Microbiology Phase 2

The stock cultures needed for quality control testing of motility are: a Salmonella typhimurium/Escherichia coli b Escherichia coli/Pseudomonas aeruginosa c Serratia marcescens/Escherichia coli d Klebsiella pneumoniae/Escherichia coli

d Klebsiella pneumoniae/Escherichia coli d Of the organisms listed only Klebsiella pneumoniae is nonmotile.

Which of the following antibiotics would routinely be tested and reported for isolates of Pseudomonas aeruginosa? a penicillin b erythromycin c clindamycin d gentamicin

d gentamicin d Aminoglycoside antibiotics such as gentamicin are active against Pseudomonas and routinely tested and reported on these isolates. Penicillin, erythromycin, and clindamycin are not active against Pseudomonas.

Refer to the following image: (IMAGE) Trophozoites of the cyst shown above are likely to: a contain red blood cells b have clear, pointed pseudopodia c contain few, if any, vacuoles d have slow, undefined motility

d have slow, undefined motility d Trophozoites of Entamoeba coli demonstrate slow and undefined motility.

Definitive identification of Neisseria gonorrhoeae is made with the. a Gram stain b oxidase test c degradation of amino acids d hydrolysis of carbohydrates

d hydrolysis of carbohydrates d Of the choices provided, only fermentation of carbohydrates provides definitive identification of Neisseria gonorrhoeae.

The expected colony count in a suprapubic urine from a healthy individual is: a 0 CFU/mL b 100 CFU/mL c 1,000 CFU/mL d 100,000 CFU/mL

a 0 CFU/mL a Urine in the bladder is normally sterile. Suprapubic aspiration removes urine directly from the bladder and yields a specimen free of urethral contamination.

How many hours after eating contaminated food do initial symptoms of staphylococcal food poisoning typically occur? a 2-6 hours b 12-18 hours c 24-48 hours d 72 hours to a week

a 2-6 hours a Staphylococcus aureus produces an enterotoxin that is associated with food poisoning. Symptoms typically appear within 2-6 hours.

The scolex of Taenia saginata has: a 4 suckers b no suckers and 14 hooklets c 24 hooklets d 26-28 sucking discs

a 4 suckers a The scolex of Taenia saginata is square with 4 suckers and no hooks.

Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42°C in an atmosphere containing: a 6% 02> 10%-15% C02, 85%-90% nitrogen b 10% H2, 5% C02, 85% nitrogen c 10% H2, 10% C02, 80% nitrogen d 25% 02, 5% C02, 70% nitrogen

a 6% 02> 10%-15% C02, 85%-90% nitrogen a Campylobacter is microaerophilic, and requires a decreased oxygen and increased carbon dioxide atmosphere for growth.

The Gram stain of drainage from a pulmonary sinus tract shows many WBCs and 3+ branching gram-positive bacilli. Colonies grow on anaerobic media after 3 days incubation. They are yellow-tan and have a molar tooth appearance. The most likely genus is: a Actinomyces b Bacteroides c Fusobacterium d Nocardia

a Actinomyces a Bacteroides and Fusobacterium are anaerobic gram-negative bacilli and Nocardia is an aerobic gram-positive bacillus stain and colony morphology described classic for Actinomyces.

Which of the following pairs of organisms usually grow on kanamycin, vancomycin, laked blood agar? a Bacteroides and Prevotella b Mobiluncus and Gardnerella c Porphyromonas and Enterococcus d VeiUonella and Capnocytophaga

a Bacteroides and Prevotella a Kanamycin-vancomycin laked blood agar is a selective medium used for the isolation of Bacteroides or Prevotella.

A Wright stain on a conjunctival smear from a neonate shows granular cytoplasmic perinuclear inclusions. This is indicative of: a Chlamydia trachomatis b herpes simplex virus c cytomegalovirus d varicella-zoster virus

a Chlamydia trachomatis a The presence of typical intracytoplasmic inclusions are particularly useful in diagnosing Chlamydia trachomatis inclusion conjunctivitis. Multinucleated giant cells are seen in cells infected with herpes simplex and varicella zoster virus. Cytomegalovirus produces large cells with intranuclear inclusions.

The reverse CAMP test, lecithinase production, double zone hemolysis, and Gram stain morphology are all useful criteria in the identification of: a Clostridium perfringens b Streptococcus agalactiae c Propionibacterium acnes d Bacillus anthracis

a Clostridium perfringens a The reverse CAMP test, production of lecithinase, and demonstration of double zone hemolysis are tests and characteristics used for the identification of Clostridium perfringens.

A strict anaerobe that produces terminal spores is: a Clostridium tetani b Corynebacterium diphtheriae c Bacillus anthracis d Propionibacterium acnes

a Clostridium tetani a Corynebacterium species and Propionibacterium species do not produce spores, and Bacillus is an aerobic organism.

An organism that demonstrates budding yeast cells with wide capsules m an India ink piepaiation of pinal fluid is probably: a Cryptococcus neoformans b Histoplasma capsulatum c Blastomyces dermatitidis d Candida albicans

a Cryptococcus neoformans a Cryptococcus neoformans is a cause of meningitis in immunocompromised patients, and produces a polysaccharide capsule.

An HIV-positive patient began to show signs of meningitis. A spinal fluid was collected and cultured for bacteria and fungus. A budding, encapsulated yeast was recovered. Which organism is consistent with this information? a Cryptococcus neoformans b Aspergillus fumigatus c Microsporum audouinii d Sporothrix schenckii

a Cryptococcus neoformans a Cryptococcus neoformans is a of meningitis in immunocompromised patients, and produces a polysacchar.de capsule.

Which ot the following sets of tests best differentiates Salmonella and Citrohacter species? a KCN, malonate, beta-galactosidase, lysine decarboxylase b dulcitol, citrate, indole, H2S production c lactose, adonitol, KCN, motility d lysine decarboxylase, lactose, sucrose, malonate, indole

a KCN, malonate, beta-galactosidase, lysine decarboxylase a Salmonella are positive for lysine decarboxylase and most are negative for KCN, malonate, and ONPG. Citrobacter are negative for lysine decarboxylase and positive for growth in KCN.

Which one of the following species of Mycobacterium does not usually fluoresce on fluorochrome stain? a Mycobacterium fortuitum b Mycobacterium tuberculosis c Mycobacterium ulcerans d Mycobacterium bovis

a Mycobacterium fortuitum a Rapidly-growing mycobacteria such as Mycobacterium fortuitum may be <10% acid fast and may not stain with fluorochrome

Which of the following reagents should be used as a mucolytic, alkaline reagent for digestion and decontamination of a sputum for mycobacterial culture? a N-acetyl-L-cystine and NaOH b NaOH alone c zephiran-trisodium phosphate d oxalic acid

a N-acetyl-L-cystine and NaOH a The most widely used digestion- decontamination method is the N-acetyl-L- cysteine-2% NaOH method.

Which of the following is a dimorphic fungus? a Sporothrix schenckii b Candida albicans c Cryptococcus neoformans d Aspergillus fumigatus

a Sporothrix schenckii a Dimorphism differentiates Sporothrix from the other fungi listed.

The recovery of some Cryptococcus species may be compromised if the isolation media contains: a cycloheximide b gentamicin c chloramphenicol d penicillin

a cycloheximide a Cycloheximide is known to inhibit the growth of some fungal pathogens, including Cryptococcus neoformans.

This structure depicts a: a cyst of a nonpathogenic amoeba b trophozoite of a nonpathogenic amoeba c cyst of a pathogenic amoeba d trophozoite of a pathogenic amoeba

a cyst of a nonpathogenic amoeba a The image displays the cyst form of Entamoeba coli, a nonpathogenic parasite.

The most meaningful laboratory procedure in confirming the diagnosis of clinical botulism is: a demonstration of toxin in the patients serum b recovery of Clostridium botulinum from suspected food c recovery of Clostridium botulinum from the patients stool d Gram stain of suspected food for gram-positive, sporulating bacilli

a demonstration of toxin in the patients serum a Botulism infection is confirmed by reference laboratories such as the CDC by demonstrating toxin in serum, feces, gastric contents or vomitus.

Refer to the following image: (IMAGE) A 24-year-old woman, who just returned from vacationing in Russia, became ill with steatorrheal diarrhea. The above organism was found in her stool. The patient most likely is suffering from: a giardiasis b amebiasis c ascariasis d balantidiasis

a giardiasis a Diarrhea associated with lamblia is caused by the consumption of contaminated water and results in greasy, foul-smelling stools.

The preferred carbon source for mycobacteria is: a glycerol b glucose c fatty acids d casein hydrolysate

a glycerol a Mycobacteria use glycerol as a carbon source in the presence of mineral salts.

Structures important in the microscopic identification of Coccidioides immitis are: a irregular staining, barrel-shaped arthrospores b tuberculate, thick-walled macroconidia c thick-walled sporangia containing sporangiospores d small pyriform microconidia

a irregular staining, barrel-shaped arthrospores a Cultures of Coccidioides immitis produce alternating arthrospores.

Plesiomonas shigelloides is a relatively new member of the family Enterobacteriaceae. What characteristic separates it from other members of the Enterobacteriaceae? a it is oxidase positive b it ferments glucose c it produces pyocyanin d it requires 10% CO2 for growth

a it is oxidase positive a Enterobacteriaceae ferment glucose and are oxidase negative. Plesiomonas was a member of the Vibrio family in part because it is oxidase positive. However, it was moved to the Enterobacteriaceae family despite its positive oxidase reaction.

Which of the following is most often used to prepare a slide from a plate culture of a dermatophyte for microscopic observation? a lactophenol cotton blue b potassium hydroxide c iodine solution d Gram stain

a lactophenol cotton blue a Lactophenol cotton blue is used as the mounting medium, since lactic acid acts as a clearing agent, phenol acts as a killing agent, glycerol prevents drying, and cotton blue gives color to the structures.

A liquid stool specimen is collected at 10:00 PM and brought to the laboratory for culture and ova and parasite examination. It is refrigerated until 10:10 AM the next day, when the physician requests that the technologist look for amoebic trophozoites. The best course of action would be to: a request a fresh specimen b perform a concentration on the original specimen c perform a trichrome stain on the original specimen d perform a saline wet mount on the original specimen

a request a fresh specimen a Protozoan trophozoites are fragile and begin to disintegrate as soon as they are passed. Liquid stool specimens should be preserved within 30 minutes of passage in order to adequately preserve parasite morphology. If a liquid specimen cannot be properly preserved, another specimen should be collected.

Which of the following is considered a primary drug for the treatment of Mycobacterium tuberculosis? a rifampin b kanamycin c rifabutin d ethionamide

a rifampin a Primary drugs for the treatment of Mycobacterium tuberculosis include isoniazid, rifampin, pyrazinamide, and ethambutol.

Ureaplasma urealyticum are difficult to grow in the laboratory on routine media because of their requirement for: a sterols b horse blood c ferric pyrophosphate d surfactant such as Tween - 80

a sterols a Ureaplasma urealyticum, like other Mycoplasma, lacks a cell wall and possesses an extremely small genome. As a result, this organism has limited biosynthetic capabi ity and fastidious growth requirements. Culture medium should contain serum (provides sterols), growth factors such as yeast extra and a metabolic substrate.

A blood culture bottle with macroscopic signs of growth is Gram stained and the technician notes small, curved gram-negative bacilli resembling "gull wings." It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent. The next step should be to: a subculture the bottle, and incubate in microaerophilic conditions b assume the organism is nonviable, and ask for repeat specimen c utilize a pyridoxal disk to detect Aeromonas d subculture the bottle to a medium containing X and V factors

a subculture the bottle, and incubate in microaerophilic conditions a Campylobacter are gram-negative, curved bacilli that require microaerophilic conditions for growth.

A gastroenterologist submits a gastric biopsy from a patient with a peptic ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to whic media? a urea broth b tetrathionate c selenite d tryptophan

a urea broth a Helicobacter pylori produces large amounts of extracellular urease and is positive for urea within 2 hours.

Chlamydial infections have been implicated in. a urethritis and conjunctivitis b gastroenteritis and urethritis c neonatal pneumonia and gastroenteritis d neonatal meningitis and conjunctivitis

a urethritis and conjunctivitis a Chlamydia trachomatis is a well-known cause of sexually transmitted infections, including urethritis and cervicitis, as well as inclusion conjunctivitis and pneumonia in neonates. It also causes trachoma and lymphogranuloma venereum.

An AFB broth culture is positive for acid-fast bacilli at 1 week while the agar slant shows no growth. The most likely explanation for this is: a the organism is a contaminant b AFB grow more rapidly in liquid media c PANTA was added to the broth d the agar slant was incubated in 5% CO2

b AFB grow more rapidly in liquid media b Liquid medium is recommended to provide more rapid recovery of AFB than solid medium. Isolation rates of mycobacteria is also higher with liquid medium.

An organism from a peritoneal abscess is isolated on kanamycin-vancomycin laked blood agar and grows black colonies on BBE agar. It is nonpigmented, catalase positive, and indole negative. The genus of this organism is: a Acidominococcus b Bacteroides c Porphyromonas d Prevotella

b Bacteroides b Bacteroides fragilis grows on BBE agar and because it can hydrolyze esculin produces black colonies. B fragilis is also catalase positive and indole negative.

A patient is suspected of having amebic dysentery. Upon microscopic examination of a fresh fecal specimen for ova and parasites, the following data were obtaine a trophozoite of 25 pm progressive, unidirectional crawl evenly distributed peripheral chromatin finely granular cytoplasm This information probably indicates: a Entamoeba coli b Entamoeba histolytica c Endolimax nana d Iodamoeba butschlii

b Entamoeba histolytica b The trophozoite of Entamoeba histolytica ranges in size from 12-60 pm, which is significantly larger than Endolimax nana. The nucleus of E histolytica displays evenly distributed peripheral chromatin unlike E coli, which has coarse peripheral chromatin and I butschlii, which has none.

A 27-year-old scuba diver has an abrasion on his left thigh. A culture of this wound grew an acid-fast organism at 30°C. This isolate most likely is: a Mycobacterium chelonae b Mycobacterium marinum c Mycobacterium tuberculosis d Mycobacterium xenopi

b Mycobacterium marinum b Mycobacterium marinum causes infections as a result of trauma to the skin and exposure to contaminated fish tanks or salt water. Its optimal growth temperature is 28e-30°C.

Coagglutination is associated with: a Chlamydia trachomatis b Neisseria gonorrhoeae c Streptococcus pneumoniae d Klebsiella pneumoniae

b Neisseria gonorrhoeae b One of the less commonly used methods for identification of Neisseria gonorrhoeae grown in culture is coagglutination.

An autopsy performed on an 8-year-old child revealed Waterhouse-Friderichsen syndrome. Blood and throat cultures taken just prior to death were positive for which organism? a Neisseria gonorrhoeae b Neisseria meningitidis c Haemophilus influenzae d Klebsiella pneumoniae

b Neisseria meningitidis b Waterhouse-Friderichsen syndrome is a known complication of severe Neisseria meningitidis infection.

Children who have infections with beta-hemolytic streptococci can develop: a acute pyelonephritis b acute glomerulonephritis c chronic glomerulonephritis d nephrosis

b acute glomerulonephritis b Noninfectious sequelae associated with infection with Streptococcus pyogenes are glomerulonephritis and rheumatic fever.

Colds and other acute respiratory diseases are most often associated with: a Epstein-Barr virus b adenovirus c coxsackie B d reovirus

b adenovirus b Adenovirus infections are common. It causes up to 5% of all respiratory infections, and the prevalence of infection is higher (up to 14%).

The diagnosis of Neisseria gonorrhoeae in females is best made from: a clinical history b an endocervical culture c a Gram stain of cervical secretions d examination for clue cells

b an endocervical culture b Clinical history does not distinguish Neisseria gonorrhoeae from Chlamydia trachomatis. Because of the presence of nonpathogenic Neisseria in the female genital tract, Gram stain does not differentiate these organisms from Ngonorrhoeae. Culture of an appropriate genital tract specimen is required to confirm identification.

A sputum specimen received at 8 AM for an AFB smear reveals acid- fast bacilli. An additional sputum is submitted that afternoon. This specimen was concentrated by the NALC-sodium hydroxide method and inoculated on 2 Lowenstein-Jensen slants and held for 8 weeks at 35°C in 5%-10% C02. No growth occurs. The best explanation is that: a the hypochlorite technique was not used b an improper specimen was submitted for culture c improper media was used for culture d cultures were held for an insufficient period of time

b an improper specimen was submitted for culture b Early-morning sputum specimens are optimal for AFB culture.

Psittacosis is transmissible to man via contact with. a insects b birds c cattle d dogs

b birds b Chlamydophila psittaci, the agent of psittacosis, is transmitted to humans via inhalation of nasal secretions, as well as infected fecal or feather dust, of psittacine birds (parrot family).

An unusual number of Mycobacterium gordonae have been isolated. The most likely souice is. a an outbreak of infections due to Mycobacterium goidonae b contamination by water organisms c contamination of commercial Lowenstein- Jensen tubes d contamination of the specimen collection containers

b contamination by water organisms b Mycobacterium gordonae is widely distributed in soil and water, and is generally considered nonpathogenic.

Which of the following procedures should be performed to confirm that an unknown mold is one of the pathogenic dimorphic fungi: a animal inoculation b culture conversion to yeast form c demonstration of sexual and asexual reproduction d serological studies

b culture conversion to yeast form b Several monomorphic molds resemble the filamentous phase of dimorphic molds, so conversion to yeast phase must be performed for identification of dimorphic molds.

In a suspected case of Hansen disease (leprosy), a presumptive diagnosis is established by: a isolation of organisms on Lowenstein-Jensen medium b detection of weakly acid-fast bacilli in infected tissue c isolation of organisms in a cell culture d detection of niacin production by the isolated bacterium

b detection of weakly acid-fast bacilli in infected tissue b Mycobacterium leprae cannot be cultured in vitro. A clinical diagnosis is made, supported by the presence of AFB in a biopsy specimen.

Photochromogens produce pigment when: a kept in the dark at 22°C b exposed to light for 1 hour c grown in the presence of CO2 d incubated with x-ray film

b exposed to light for 1 hour b Pigment production is controlled by an oxygen-dependent, light-inducible enzyme in photochromogenic mycobacteria.

Refer to the following image: (IMAGE) The organism depicted is a(n): a amoeba b flagellate c filaria d sporozoan

b flagellate b The image displays the trophozoite form of Giardia lamblia, a flagellated protozoan parasite.

The stock cultures needed for quality control testing of oxidase production are: a Escherichia coli/Klebsiella pneumoniae b Salmonella typhimurium/Escherichia coli c Escherichia coli/Pseudomonas aeruginosa d Proteus mirabilis/Escherichia coli

c Escherichia coli/Pseudomonas aeruginosa c Of the organisms listed only Pseudomonas aeruginosa is oxidase positive.

An acid-fast bacillus recovered from an induced sputum had the following characteristics: pigmentation: yellow in the dark, turning a deeper yellow-orange after 2 weeks of light exposure nitrate reduction: negative Tween® hydrolysis: positive at 5-10 days urease: negative Based on this information, the organism is most likely Mycobacterium: a scrofulaceum b gordonae c szulgai d fiavescens

b gordonae b The characteristics given differentiate Mycobacterium gordonae from the other mycobacteria listed. M szulgai and flavescens are nitrate reduction positive, and M scrofulaceum is negative for Tween® hydrolysis.

A beta-hemolytic streptococci that is bacitracin-sensitive and CAMP-negative is: a group B b group A c beta-hemolytic, not group A, B, or D d beta-hemolytic, group D

b group A b Group A streptococci (Streptococcus pyogenes) are susceptible to bacitracin and CAMP test negative.

Encephalitis is most commonly associated with which of the following viruses? a Epstein-Barr b herpes simplex c coxsackie B d varicella zoster

b herpes simplex b Herpes simplex virus is the most common cause of fatal sporadic encephalitis in the United States.

A gram-negative diplococcus that grows on modified Thayer-Martin medium can be further confirmed as Neisseria gonorrhoeae if it is. a oxidase positive, glucose positive, and maltose positive b oxidase positive and glucose positive, maltose negative c oxidase positive and maltose positive, glucose negative d glucose positive, oxidase negative and maltose negative

b oxidase positive and glucose positive, maltose negative b Neisseria gonorrhoeae is oxidase positive and ferments glucose but not maltose.

The genus of virus associated with anogenital warts, cervical dysplasia and neoplasia a herpes simplex virus b papillomavirus c cytomegalovirus d coxsackievirus

b papillomavirus b Human papilloma virus (HPV) infects epithelial tissues throughout the body, including skin, larynx, and anogenital tissue. Persistent infection with oncogenic types of HPV and integration of HPV DNA into the cellular genome is a pathway leading to HPV- induced neoplasia, such as cervical cancer.

When staining acid-fast bacilli with Truant auramine-rhodamine stain, potassium permanganate is used as a: a decolorizing agent b quenching agent c mordant d dye

b quenching agent b The counterstain acts as a quenching agent and reduces the background fluorescence of cellular debris.

The mycobacteria that produce a deep yellow or orange pigment both in the dark and light are: a photochromogens b scotochromogens c nonchromogens d rapid growers

b scotochromogens b Scotochromogens produce deep yellow or orange pigment when grown in either light or darkness.

A stool specimen for ova and parasite examination contained numerous rhabditiform larvae. Which factor does not aid in the identification of larvae? a larva tail morphology b type of water vegetation consumed c length of the buccal cavity d appearance of the genital primordium

b type of water vegetation consumed b The rhabditiform larvae of hookworm and Strongyloides stercoralis can be differentiated by the size of their genital primordium. Strongyloides has a prominent genital primordium and a small buccal cavity. Hookworm larvae have a longer buccal cavity, and the genital primordium is not evident. S. stercoralis larvae have a notched tail whereas hookworm larvae have a tapering tail.

A 2-week-old culture of a urine specimen produced a few colonies of acid-fast bacilli, which were q!£y rough and nonpigmented. The niacin test was weakly positive and the nitrate test was positive. Which of the following is the most appropriate action when a presumptive identification has been requested as soon as possible? a report the organism as presumptive Mycobacterium tuberculosis b wait a few days and repeat the niacin test; report presumptive Mycobacterium tuberculosis if the test is more strongly positive c subculture the organism and set up the routine battery of biochemicals; notify the physician that results will not be available for 3 weeks d set up a thiophene-2-carboxylic acid hydrazide (T2H); if the organism is sensitive, report Mycobacterium bovis

b wait a few days and repeat the niacin test; report presumptive Mycobacterium tuberculosis if the test is more strongly positive b The niacin test can be repeated in several days from the initial tube rather than setting up new biochemicals that would take longer

Acinetobacter Iwoffii differs from Neisseria gonorrhoeae in that the former: a exhibits a gram-negative staining reaction b will grow on MacConkey and EMB media c is indophenol oxidase-positive d produces hydrogen sulfide on a TSI slant

b will grow on MacConkey and EMB media b Both organisms are gram-negative. Neisseria gonorrhoeae is fastidious and does not grow on MacConkey or EMB agar, but Acinetobacter does. Neisseria is oxidase positive and Acinetobacter is oxidase negative.

An organism gave the following reactions: TSI: acid slant/acid butt; no H2S gas produced indole: positive motility: positive citrate: negative lysine decarboxylase: positive urea: negative VP: negative This organism most likely is: a Klebsiella pneumoniae b Shigella dysenteriae c Escherichia coli d Enterobacteria cloacae

c Escherichia coli c These biochemicals are characteristic for E coli. Klebsiella pneumoniae is indole negative and nonmotile. Shigella dysenteriae is nonmotile and Enterobacter cloacae is indole negative.

Which of the following is the most useful morphological feature in identifying the mycelial phf of Histoplasma capsulatum? a arthrospores every other cell b 2-5 pm microspores c 8-14 pm tuberculate macroconidia d 5-7 pm nonseptate macroconidia

c 8-14 pm tuberculate macroconidia c The presence of tuberculate macroconidia indicates a presumptive identification of H capsulatum. The identification must be confirmed using nucleic acid probes or exoantigen testing.

A 64-year-old male with lymphoma has a positive blood culture at 18 hours incubation. The organism is a nonlactose fermenting gram-negative bacillus on MacConkey agar. Further testing gives the following reactions: oxidase: negative TSI: alkaline/acid, no hydrogen sulfide motility: positive indole: positive citrate: positive ornithine decarboxylase: negative urea: positive phenylalanine deaminase: positive VP: negative The genus is: a Morganella b Proteus c Providencia d Serratia

c Providencia c These are typical biochemical reactions for Providencia. Key reactions that sepaiate it from most other enteric organisms aie lack of hydrogen sulfide production and phenylalanine deaminase positivity. Citrate and ornithine reactions differentiate Providencia and Morganella.

An organism was inoculated to a TSI tube and gave the following reactions: alkaline slant/acid butt, H2S, gas produced This organism most likely is: a Klebsiella pneumoniae b Shigella dysenteriae c Salmonella typhimurium d Escherichia coli

c Salmonella typhimurium c Salmonella is the only distractor that produces H2S. Also, Klebsiella and E coli produce acid/acid reactions in TSI.

Establishing the pathogenicity of a microorganism isolated from a child's throat and identified as Corynebacterium diphtheria would depend upon: a the morphological appearance as revealed by Gram stain b the type of hemolysis on blood agar c a positive toxigenicity test d the appearance of growth on Tinsdale tellurite agar

c a positive toxigenicity test c In order to determine if an isolate of Corynebacterium diphtheriae produces toxin, testing for the presence of diphtheria toxin mttst be performed using methods such as the Elek test or PCR.

Proper collection of a sample for recovery of Enterobius vermicular is include a a 24-hour urine collection b a first morning stool collection with proper preservative c a scotch tape preparation from the perianal region d peripheral blood from a finger

c a scotch tape preparation from the perianal region c The ova of Enterobius vermicularis cannot be demonstrated in a routine ova and parasite examination. The adult female Enterobius worm migrates out of the anus, and lays her eggs in the perianal folds. A scotch tape preparation of the skin of the perianal folds is used to collect ova.

Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection? a blood b urine c bone marrow d lymph node

c bone marrow c Bone marrow is considered the most sensitive specimen for the recovery of Brucella.

The disease-producing capacity of Mycobacterium tuberculosis depends primarily upon: a production of exotoxin b production of endotoxin c capacity to withstand intracellular digestion by macrophages d lack of susceptibility to the yeloperoxidase system

c capacity to withstand intracellular digestion by macrophages c Mycobacterium tuberculosis can remain viable but dormant in macrophages for many years.

The primary isolation of Neisseria gonorrhoeae requires: a anaerobic conditions b starch media c carbon dioxide d blood agar

c carbon dioxide c Neisseria gonorrhoeae requires an enhanced C02 atmosphere for optimal growth.

A nonchromogen that grows best at 42°C and is highly resistant to antibiotics is: a Mycobacterium chelonae b Mycobacterium marinum c Mycobacterium tuberculosis d Mycobacterium xenopi

d Mycobacterium xenopi d Mycobacterium xetiopi grows best at 42°-45°C and is not pigmented.

The most critical distinction between Staphylococcus aureus and other Staphylococcus is: a phosphatase reaction b DNA production c coagulase production d hemolysis

c coagulase production c Coagulase production is the primary biochemical used to differentiate S aureus from other coagulase-negative staphylococci.

The most sensitive test for the initial diagnosis of cryptococcal disease is: a India ink b Gram stain c cryptococcal antigen d Giemsa stain

c cryptococcal antigen c Cryptococcal latex antigen test has been proven to be significantly more sensitive than staining methods.

A yellow colony from a wound culture tested catalase-positive and coagulase-negative. The organism stained as gram-positive cocci in clusters. Which of the following tests would differentiate between a coagulase-negative Staphylococcus and Micrococcus? a novobiocin susceptibility b leucine aminopeptidase production c furazolidone (100 pg/disk) susceptibility d bile esculin

c furazolidone (100 pg/disk) susceptibility c Micrococcus and Staphylococcus can be differentiated by susceptibility to furazolidone (100 pg/disk). Staphylococcus is susceptible and Micrococcus is resistant.

The following results were obtained from a culture of unknown origin: Gram stain: gram-negative diplococci indophenol oxidase: positive glucose: positive maltose: negative sucrose: negative The most likely source of the specimen would be the: a respiratory tract b blood c genitourinary tract d cerebrospinal fluid

c genitourinary tract c Based on the biochemicals listed the most likely identification of the organism is Neisseria gonorrhoeae. N gonorrhoeae is most commonly isolated from the genitourinary tract.

A beta-hemolytic Streptococcus that is bacitracin-resistant and CAMP-positive is: a group A or B b group A c group B d beta-hemolytic, group D

c group B c Group B streptococci (Streptococcus agalactiae) are resistant to bacitracin and CAMP test positive.

A sputum specimen from a patient with a known Klebsiella pneumoniae infection is received in the laboratory for fungus culture. The proper procedure for handling this specimen is to: a reject the current specimen and request a repeat culture when the bacterial organism is no longer present b incubate culture tubes at room temperature in order to inhibit the bacterial organism c include media that have cycloheximide and chloramphenicol added to inhibit bacterial organisms and saprophytic fungi d perform a direct PAS stain; if no fungal organisms are seen, reject the specimen

c include media that have cycloheximide and chloramphenicol added to inhibit bacterial organisms and saprophytic fungi c Since fungi grow more slowly than bacteria, a medium with antimicrobials is included to assist in the recovery of fungi. Chloramphenicol is an antibacterial agent active against Klebsiella and most other bacteria.

Mycoplasmas differ from bacteria in that they: a do not cause disease in humans b cannot grow in artificial inanimate media c lack cell walls d are not serologically antigenic

c lack cell walls c Mycoplasma are smaller than other bacteria and lack a cell wall. Instead, they possess a trilaminar cell membrane. Because they lack a cell wall, they cannot be stained with Gram stain.

Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningitidis? a acid from maltose b growth on modified Thayer-Martin agar c lactose degradation d nitrite reduction to nitrogen gas

c lactose degradation c Both Neisseria meningitidis and N lactamica produce acid from maltose and grow on modified Thayer martin agar- N lactamica ferments lactose, N meningitidis does not.

A beta-hemolytic gram-positive coccus was isolated from the cerebrospinal fluid of a 2-day-old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disc. Which of the following should be performed for the identification of the organism? a oxidase production b catalase formation c latex antigen typing d esculin hydrolysis

c latex antigen typing c The most likely organism isolated from this specimen is Streptococcus agalactiae. Polysaccharide antigen typing will confirm the identification of S agalactiae and differentiate it from other beta-hemolytic streptococci.

MacConkey media for screening suspected cases of hemorrhagic E coli 0157:117 must contain: a indole b citrate c sorbitol d lactose

c sorbitol c Sorbitol replaces lactose in MacConkey. E coli 0157:H7 does not ferment sorbitol, whereas other species of E coli are positive for fermentation of sorbitol. This makes the media a good screen for 0157:H7.

When stool examination is negative, the preferred specimen for the diagnosis of paragonimiasis is: a bile drainage b duodenal aspirate c sputum d rectal biopsy

c sputum c Adult Paragonimus worms live in cystic cavities in the lungs. Eggs are laid by the adult and transferred to the bronchial tree with sputum. Ova may be found in sputum or swallowed and passed in stool.

The following growth results were observed on media inoculated with a foot abscess aspirate and incubated in 3%-5% CO2. SBA: 2+ large gray colonies PEA: no growth chocolate: 3+ large gray colonies MacConkey: 3+ lactose fermenters trypticase soy broth: gram-negative bacilli and gram-positive bacilli Biochemicals were set up on the colonies from the MacConkey agar plate. What should the microbiologist do next? a set up biochemicals on the colonies from SBA b send out final report to the physician after biochemicals are interpreted c subculture TSB to SBA aerobic and SBA anaerobic d test colonies on chocolate agar with hemin and NAD

c subculture TSB to SBA aerobic and SBA anaerobic C In this culture there is an aerobic or facultative gram-negative bacillus and a second organism growing in the TSB only (a gram-positive bacillus). This leads one to think it could be an anaerobe because it did not grow on any of the media incubated in 3%-5% C02. The aerotolerance test is the first step in determining if an anaerobe is present.

The porphyrin test was devised to detect strains of Haemophilus capable of: a ampicillin degradation b capsule production c synthesis of hemin d chloramphenicol resistance

c synthesis of hemin c The porphyrin test is an alternative method for detecting heme-producing species of Haemophilus. It detects whether or not the organism converts the substrate delta-amino levulinic acid into porphyrins porphobilinogen, which are intermediates synthesis of Factor X.

Pemcillium species is isolated from a bone marrow culture of a patient that travelled to southeast Asia. After 7 days the isolate produces a red pigment that diffuses into the medium. The technologist should: a prepare a slide culture b repeat the tease preparation c transfer a colony to BHI at 35°C d perform a nucleic acid probe

c transfer a colony to BHI at 35°C c Penicillium marneffeiis a dimorphic fungi only that produces a diffusible red pigment.

A positive niacin test is most characteristic of Mycobacterium: a chelonae b marinum c tuberculosis d xenopi

c tuberculosis c A positive niacin test differentiates only Mycobacterium tuberculosis from most other mycobacteria.

A digested and decontaminated sputum is inoculated into a Bactec™ 12B bottle and incubated in air at 37°C. On day 14, a positive growth index is obtained, and the auramine-rhodamine stain is positive. Broth from the initial bottle is inoculated into one Bactec™ 12B bottle, and one Bactec™ 12B bottle with NAP. After reincubation, the inoculated growth bottle shows an increase in growth index, while the bottle containing NAP shows no increase. The organism cultured from the sputum is most likely Mycobacterium: a marinum b kansasii c tuberculosis d avium-intracellulare

c tuberculosis c Mycobacterium tuberculosis and M bovis cannot grow in the presence of NAP, while other mycobacteria can grow in the presence of NAP.

A urine culture from a patient with a urinary tract infection yields a yeast culture with the following characteristics: failure to produce germ tubes hyphae not formed on cornmeal agar urease-negative assimilates trehalose The most likely identification is: a Saccharomyces cerevisiae b Cryptococcus laurentii c Candida pseudotropicalis d Candida glabrata

d Candida glabrata d Of the yeasts listed, only UCandida glabrata is urease negative and does not produce pseudohyphae.

Lab workers should always work under a biological safety hood when working with cultures of: a Streptococcus pyogenes b Staphylococcus aureus c Candida albicans d Coccidioides immitis

d Coccidioides immitis d The arthroconidia of Coccidioides immitis are highly infectious; cultures must be handled with care to minimize aerosols.

Staib medium (birdseed agar) is useful in the identification of which of the following? a Candida albicans b Candida glabrata c Saccharomyces cerevisiae d Cryptococcus neoformans

d Cryptococcus neoformans d Cryptococcust neoformas is the only yeast that produces brown colonies (due to melanin production) on birds agar.

Differentiation of Mycobacterium avium from Mycobacterium intracellulare can be accomplished by: a nitrate reduction test b Tween® hydrolysis test c resistance to 10 pg thiophene-2-carboxylic acid hydrazide (TCH) d DNA probe

d DNA probe d Mycobacterium avium and M intracellulare have the same biochemical pattern, but can be differentiated by the use of DNA probes.

When grown in the dark, yellow to orange pigmentation of the colonies is usually demonstrated by: a Mycobacterium tuberculosis b Mycobacterium kansasii c Mycobacterium fortuitum d Mycobacterium scrofulaceum

d Mycobacterium scrofulaceum d Mycobacterium scrofulaceum is a only scotochromogen.

A branching gram-positive, partially acid-fast organism is isolated from a bronchial washing on a 63-year-old woman receiving chemotherapy. The organism does not hydrolyze casein, tyrosine or xanthine. The most likely identification is: a Actinomadura madurae b Nocardia caviae c Streptomyces somaliensis d Nocardia asteroides

d Nocardia asteroides d Nocardia asteroides are partially acid fast, and do not hydrolyze the substrates casein, tyrosine, or xanthine.

Which one of the following gram-negative bacilli ferments glucose? a Alcaligenes faecalis b Pseudomonas cepacia c Acinetobacter Iwoffii d Yersinia enterocolitica

d Yersinia enterocolitica d Alcaligenes, Pseudomonas and Acinetobacter are all nonfermenters; Yersinia is a member of the Enterobacteriaceae and, by definition, ferments glucose.

A 10-year-old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory results were obtain . . Patient value Normal range % segmented neutrophils 75% 16%-60% WBC count 200 x 13^3/uL (200x10^9/L) 13.0 x 10^3/uL (13.0 x 10^9/L) The admitting diagnosis was appendicitis. During surgery the PP re isolated from the room enlarged node was removed and cultured. Small gram-negative bacilli were temperature plate. The organism most likely is. a Prevotella melaninogenica b Shigella sonnei c Listeria monocytogenes d Yersinia enterocolitica

d Yersinia enterocolitica d The history of the patient suggests an appendicitis-like syndrome, which is consistent with Yersinia enterocolitica. Also, Yenterocolitica grows better at 25°C.

A 25-year-old man who had recently worked as a steward on a transoceanic grain ship presented to the emergency room with high fever, diarrhea and prostration. Axillary lymph nodes were hemorrhagic and enlarged. A Wayson stain of the aspirate showed bacilli that were bipolar resembling safety pins. The most likely identification of this organism is: a Brucella melitensis b Streptobacillus moniliformis c Spirillum minus d Yersinia pestis

d Yersinia pestis d Yersinia pestis is classically described as having a "safety pin" appearance on Wayson stain. This patient's presentation is classic for bubonic plague.

Hie etiologic agent of botulism is: a highly motile b non-spore-forming c Clostridium perfringens d an exotoxin producer

d an exotoxin producer d The toxin produced by Clostridium botulinum is a neurotoxin that is excreted by the organism in food materials, and is then ingested.

A gram-negative bacillus has been isolated from feces, and the confirmed biochemical reactions fit those of Shigella. The organism does not agglutinate in Shigella antisera. What should be done next? a test the organism with a new lot of antisera b test with Vi antigen c repeat the biochemical tests d boil the organism and retest with the antisera

d boil the organism and retest with the antisera d Some Shigella produce capsular antigen that mask the cell wall and boiling removes the capsule.

A yeast isolate from a CSF specimen produced the following results: India ink: no encapsulated yeast cells cryptococcal antigen: negative urea: negative germ tube: negative What should the technologist do next to identify this organism? a inoculate bird seed agar b ascospore stain c cycloheximide susceptibility d carbohydrate assimilation

d carbohydrate assimilation d Conventional tests, such as carbohydrate assimilation, must be performed for definitive identification of the yeast in this CSF specimen, especially in light of the fact that the yeast is both cryptococcal antigen and germ tube negative.

Tubercle bacilli are specifically stained by: a crystal violet b 1% acid fuchsin c methylene blue d carbol fuchsin

d carbol fuchsin d Mycobacteria form stable complexes with Kinyoun carbol fuchsin.

A batch of trichrome-stained slides for ova and parasite examination contains numerous minute crystals, which totally obscure the microscopic field. Which of the Mowing measures is most appropriate remedial action? a change the Schaudinn fixative, remove coverslips and lestain b change the acid alcohol and restain c remove coverslips and remount using fresh Permount or similar medium d change the iodine alcohol solution to obtain a strong tea-colored solution, restain

d change the iodine alcohol solution to obtain a strong tea-colored solution, restain d Incomplete removal of mercuric chloride may cause the smear to contain refractive crystals. Since the 70% ethanol-iodine solution removes the mercury, it should be changed at least weekly to maintain the strong tea color.

A first morning sputum specimen is received for acid-fast culture. The specimen is centrifuged, and the sediment is inoculated on 2 Lowenstein-Jensen slants, which are incubated at 35°C : 5%-10% C02. After 1 week, the slants show abundant growth over the entire surface. Stair reveal gram-negative bacilli. To avoid this problem: a utilize a medium that inhibits bacterial growth b add sodium hypochlorite to the sediment before inoculation c incubate the tubes at room temperature to retard bacterial growth d decontaminate the specimen with sodium hydroxide

d decontaminate the specimen with sodium hydroxide d Specimens contaminated by normal flora must be decontaminated prior to inoculation of media; NaOH is the most common decontaminant.

A beta-hemolytic, catalase-positive, gram-positive coccus is coagulase negative by the slide coagulase test. Which of the following is the most appropriate action in identification of this organism? a report a coagulase-negative Staphylococcus b report a coagulase-negative Staphylococcus aureus c reconfirm the hemolytic reaction on a fresh 24-hour culture d do a tube coagulase test to confirm the slide test

d do a tube coagulase test to confirm the slide test d Staphylococcus aureus are usually beta- hemolytic. Some strains may not produce bound coagulase detected by the slide coagulase test. A tube coagulase is performed to detect free coagulase and should be performed on colonies with typical S aureus morphology that are slide coagulase- negative.

Rickettsiae infecting man multiply preferentially within which of the following cells? a reticuloendothelial b hepatic c renal tubule d endothelial

d endothelial d Rickettsia species infect and multiply within vascular endothelial cells.

Its important to differentiate between Enterococcus and group D streptococcus because: a viridans streptococci are often confused with enterococci b several enterococci cause severe puerperal sepsis c group D streptococci are avirulent d enterococci often show more antibiotic resistance than group D streptococci

d enterococci often show more antibiotic resistance than group D streptococci d Enterococcus species are more resistant to antimicrobial therapy than group D streptococci such as S hovis.

Microorganisms resembling L-forms have been isolated from the blood of patients treated with antibiotics that: a complex with flagellar protein b interfere with cell membrane function c inhibit protein synthesis d interfere with cell wall synthesis

d interfere with cell wall synthesis d Bacterial L-forms are bacteria that lose their cell wall as a result of therapy with cell wall-active antibiotics, such as beta-lactam antibiotics. Unlike Mycoplasma species, which permanently lack a cell wall, the lack of a cell wall in L-forms is a result of environmental conditions. Once beta-lactam therapy is discontinued, an L-form has the capability to regrow the cell wall.

The function of N-acetyl-L-cysteine in the reagent for acid-fast digestion-decontamination procedure is to: a inhibit growth of normal respiratory flora b inhibit growth of fungi c neutralize the sodium hydroxide d liquefy the mucus

d liquefy the mucus d N-acetyl-L-cysteine (NALC) is a mucolytic agent; the concentration of NALC may be increased to digest thick, mucoid specimens.

The microscopic structures that are most useful in the identification of dei matophytes are: a septate and branching hyphae b racquet and pectinate hyphae c chlamydospores and microconidia d macroconidia and microconidia

d macroconidia and microconidia d Dermatophytes include 3 genera that are generally differentiated by their macroconidia and microconidia formation.

An isolate on chocolate agar from a patient with epiglottitis was suggestive of HaemopW/us species. Additional testing showed that the isolate required for growth and was nonhemolytic. The organism is most likely Haemophilus: a haemolyticus b ducreyi c influenzae d parainfluenzae

d parainfluenzae d Haemophilus parainfluenzae requires NAD for growth but not hemin. This distinguishes it from H influenzae. H haemolyticus is hemolytic, and H ducreyi does not cause epiglotittis.

Skin scrapings obtained from the edge of a crusty wrist lesion were found to contain thick-walled, spherical yeast cells (8-15 pm in diameter) that had single buds with a wide base of attachment. Microscopic examination of the room temperature isolate from this specimen would probably reveal the presence of: a rosette-like clusters of pear-shaped conidia at the tips of delicate conidiophores b thick-walled, round to pear-shaped tuberculate macroconidia c numerous conidia along the length of hyphae in a "sleevelike" arrangement d round or pear-shaped small conidia attached to conidiophores of irregular lengths

d round or pear-shaped small conidia attached to conidiophores of irregular lengths d The microscopic morphology of the yeast phase is characteristic of Blastomyces. The microscopic morphology of the mycelial phase of Blastomyces is round or pear-shaped small conidia attached to conidiophores of irregular lengths.

The specimen of choice for finding the above parasite is: a stool b duodenal washing c rectal swab d scotch tape preparation

d scotch tape preparation d The ova of Enterobius vermicularis cannot be demonstrated in a routine ova and parasite examination. The adult female Enterobius worm migrates out of the anus and lays her eggs in the perianal folds. A scotch tape preparation of the skin of the perianal folds is used to collect ova.

Which of the following is the best aid in the identification of Epidermophyton floccosum X£y macroconidia? a parallel side walls with at least 10 cells b spindle-shaped spore with thin walls c spindle-shaped spore, thick walls and distinct terminal knob with echinulations d smooth walls, club-shaped

d smooth walls, club-shaped d Smooth walled, club-shaped macroconidia are characteristic of Epidermophyton fioccosum.

Biochemical reactions of an organism are consistent with Shigella. A suspension is tested in antiserum without resulting agglutination. However, after 15 minutes of boiling, agglutination occurs in group D antisera. The Shigella species is: a dysenteriae b flexneri c boydii d sonnei

d sonnei d Boiling removed the capsule so that the antiserum could react with cell wall antigen. Group D Shigella is S sonnei.

Which one of the following specimen requests is acceptable? a feces submitted for anaerobic culture b Foley catheter tip submitted for aerobic culture c rectal swab submitted for direct smear for gonococci d urine for culture of acid-fast bacilli

d urine for culture of acid-fast bacilli d Urine is an appropriate specimen for the detection of renal tuberculosis. Since feces contain anaerobic organisms as part of the indigenous flora, it is an unacceptable specimen for anaerobic culture. Foley catheter tips are also not acceptable for culture, because they are contaminated with colonizing organisms. Gram stain smears of rectal swabs for Ngonorrhoeae should also not be performed, since the presence of organisms with similar morphologies may lead to overinterpretation of smears.

The procedure that assures the most accurate detection of mecA-mediated oxacillin resistance in routine broth microdilution susceptibility testing against S aureus is: a addition of 4% NaCl b incubation at 30°C c incubation for 48 hours d use of cefoxitin for testing

d use of cefoxitin for testing d Cefoxitin is used as a surrogate for mecA-mediated oxacillin resistance in S aureus. S aureus with cefoxitin MICs >4 pg/mL are considered oxacillin resistant. The Clinical Laboratory Standards Institute (CLSI) recommends addition of 2% NaCl, incubation at 35±2°C, and incubation for 24 hours when performing susceptibility testing of S aureus against oxacillin.

When using a control strain of Staphylococcus aureus, the technologist notices that the zone around the oxacillin disk is too small. Which of the following is the most likely explanation? a inoculation of the plates 10 minutes after preparing the inoculum b incubation of the Mueller-Hinton plates at 35°C c use of a 0.25 McFarland standard to prepare inoculum d use of outdated oxacillin disks

d use of outdated oxacillin disks d Deterioration of the antimicrobial agent in the disk will cause the zone sizes to be too small (falsely resistant). Standardization of the inoculum turbidity to less than a 0.5 McFarland standard would result in an inoculum that is too light and resulting zone sizes that are too large. Incubation of the plates at 35°C and inoculating plates within 10 minutes of preparation would not have an adverse effect on zone sizes.

A reliable test for distinguishing Staphylococcus aureus from other staphylococci is. a oxidase b coagulase c catalase d optochin susceptibility

b coagulase b Coagulase is the biochemical test used to distinguish S aureus (positive) from coagulase-negative staphylococci (negative).

A specimen of hair that fluoresced under a Wood lamp was obtained from a child with low-grade scaling lesions of the scalp. Cultures revealed a fungus with mycelium and very few macroconidia or microconidia. This fungus is most likely: a Microsporum gypseum b Microsporum audouinii c Trichophyton tonsurans d Epidermophyton floccosum

b Microsporum audouinii b The absence of conidia differentiates Microsporum audouinii from the other dermatophytes listed.

Protozoan cysts are found in a wet mount of sediment from ethyl-acetate concentrated material. The cysts are without peripheral chromatin on the nuclear membrane. Each cyst has 4 nuclei, and each nucleus has a large karyosome, which appears as a refractive dot. These oval cysts are most likely: a Endolimax nana b Chilomastix mesnili c Entamoeba histolytica d Entamoeba hartmanni

a Endolimax nana a While Entamoeba hartmanni and, Endolimax nana are a similar size, E hartmanni has similar peripheral chromatin to E histolytica, while E nana has none. E histolytica cysts are larger and round when compared to E nana. Chilomastix is a flagellated protozoan, and has only 1 nucleus.

An inexperienced parasitology student may confuse the above organism with. a Entamoeba histolytica b Dientamoeba fragilis c Giardia lamblia d Trichomonas vaginalis

a Entamoeba histolytica a The cysts of Entamoeba coli and E histolytica may appear similar to the unexperienced technologist. E coli cysts are larger and contain more than 4 nuclei in each cyst.

Which selective medium is used for the isolation of gram-positive microorganisms? a Columbia CNA with 5% sheep blood b trypticase soy agar with 5% sheep blood c eosin methylene blue d modified Thayer-Martin

a Columbia CNA with 5% sheep blood a Columbia CNA agar contains colistin and nalidixic acid, which inhibit most gram-negative organisms. Eosin methylene blue is selective and inhibits gram-positive organisms and modified Thayer Martin is selective and inhibits gram-positive organisms, gram-negative bacilli and yeast.

At the present time Clostridium difficile toxin can be detected by: a fluorescent staining b EIA c latex agglutination d high-pressure liquid chromatography

b EIA b Latex agglutination identifies the organism, but does not distinguish between toxigenic and nontoxigenic strains, while EIA can detect toxins. Fluorescent staining and HPLC are not used for detection of C difficile toxins.

Which organism is the most common anaerobic bacteria isolated from infectious processes of soft tissue and anaerobic bacteremia? a Bacteroides fragilis b Fusobacterium nucleatum c Porphyromonas asaccharolytica d Clostridium perfringens

a Bacteroides fragilis a Anaerobic gram-negative bacilli predominate among anaerobes in clinical infections. Bacteroides fragilis is the most common isolated anaerobic bacteria in clinical specimens.

Which one of the following anaerobes would be negative for indole? a Bacteroides fragilis b Fusobacterium nucleatum c Porphyromonas asaccharolytica d Proteus mirabilis

a Bacteroides fragilis a Bacteroides fragilis is indole negative, unlike Fusobacterium nucleatum and Porphyromonas asaccharolytica. Proteus mirabilis is an indole negative, aerobic organism.

Relapsing fever in humans is caused by: a Borrelia recurrentis b Brucella abortus c Leptospira interrogans d Spirillum minus

a Borrelia recurrentis a Relapsing fever is caused by Borrelia recurrentis and is transmitted by the human body louse. Relapsing fever is characterized by the acute onset of high fever lasting 3-7 days, interspersed with periods of no fever lasting days to weeks.

A 17-year-old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram-negative bacilli with yellow, smooth colonies that have the following biochemical reactions: oxidase: positive TSI: alk/alk glucose: oxidized fluorescence: negative lysine decarboxylase: positive The most likely organism is: a Burkholderia cepacia b Klebsiella pneumoniae c Shewanella putrefaciens d Stenotrophomonas maltophilia

a Burkholderia cepacia a Burkholderia cepacia is associated with ONLY respiratory infections in cystic fibrosis patients, and the biochemicals are typical for this organism.

A diabetic foot swab from a 82-year-old woman with recurrent infections is submitted for culture. The Gram stain reveals: many neutrophils, no squamous epithelial cells many gram-negative bacilli many gram-positive cocci in chains The physician requests that all pathogens be worked up. In addition to the sheep blood and MacConkey agar plates routinely used for wound cultures, the technologist might also process a(n): a CNA agar plate b chocolate agar plate c XLD agar plate d chopped meat glucose

a CNA agar plate a CNA agar is a selective medium rutinelly used in the isolation of gram positive aerobic and anaerobic organisms. Since the Gram stain indicates a mixture of gram-positive and gram-negative organisms, use of CNA will aid in the recovery of the gram-positive cocci in culture.

Which of the following must be incubated in a microaerophilic environment for optimal recovery of the organism? a Campylobacter jejuni b Escherichia coli c Pseudomonas aeruginosa d Proteus mirabilis

a Campylobacter jejuni a Most Campylobacter species grow best under lower oxygen tension in an atmosphere of 5% oxygen, 10% carbon dioxide and 85% nitrogen. E coli and Proteus mirabilis are facultative anaerobes and Pseudomonas aeruginosa is an aerobe.

AFB smear positive respiratory specimens may be reliably identified as Mycobacterium tuberculosis the same day the smear was read by: a cording seen on the AFB smear b nucleic acid amplification c QuantiFERON®-TB test d DNA probes

b nucleic acid amplification b Several commercial PCR tests are available that identify Mycobacterium tuberculosis from positive respiratory specimens.

Crust from a cauliflower-like lesion on the hand exhibited brown spherical bodies 6-12 mm in diameter when examined microscopically. After 3 weeks of incubation at room temperature, a slow-growing black mold grew on Sabouraud dextrose agar. Microscopic examination revealed Cladosporium, Phialophora and Fonsecaea types of sporulation. The probable identification of this organism is: a Fonsecaea pedrosoi b Pseudallescheria boydii c Phialophora verrucosa d Cladosporium carrionii

a Fonsecaea pedrosoi a Only Fonsecaea pedrosoi produces cladiosporium, phialophora and fonsecaea types of sporulation simultaneously.

An organism that exhibits the satellite phenomenon around colonies of staphylococci is. a Haemophilus influenzae b Neisseria meningitidis c Neisseria gonorrhoeae d Klebsiella pneumoniae

a Haemophilus influenzae a Haemophilus influenzae requires X and V factors. Sheep blood agar supplies X factor, and the staphylococci produce V factor, so colonies grow around staph colonies.

Sodium bicarbonate and sodium citrate are components of which of the following? a JEMBEC system b MTM agar c NYC medium d ML agar

a JEMBEC system a The JHMBEC system is a transport and inoculation medium used for direct plating of specimens for Ngonorrhoeae. Chocolate- based selective medium is inoculated with the specimen. This is placed in an impermeable plastic bag with a bicarbonate- sodium citrate pellet that absorbs moisture to generate a carbon dioxide-rich environment,

Clinical resistance to penicillin correlates most frequently with beta-lactamase production in: a Neisseria gonorrhoeae b Neisseria meningitidis c Streptococcus agalactiae d Streptococcus pyogenes

a Neisseria gonorrhoeae a Penicillin resistance in Streptococcus pyogenes and S agalactiae have not been described. Neisseria meningitidis is rarely resistant to penicillin, which can be beta-lactamase mediated in some isolates. The primary mechanism of penicillin resistance in Ngonorrhoeae is beta-lactamase.

An organism recovered from a sputum has the following characteristics: Culture: growth at 7 days on Lowenstein-Jensen agar, incubated under aerobic conditions with C02 at 35°C Gram stain: delicate branching gram-positive bacilli acid-fast stain: branching, filamentous, "partially" acid-fast bacterium These results are consistent with which of the following genera? a Nocardia b Mycobacterium c Actinomyces d Streptomyces

a Nocardia a Nocardia are capable of growing on Lowenstein-Jensen agar within 7 days and demonstrate branching, beaded gram- positive bacilli on Gram stain. Nocardia are partially acid fast, and are stained best with the modified acid-fast stain.

In the USA, the most common organism causing eumycotic mycetoma is: a Pseudallescheria boydii b Nocardia brasiliensis c Blastomyces dermatitidis d Aspergillus fumigatus

a Pseudallescheria boydii a Pseudallescheria boydii is a common cause ONLY of eumycotic mycetoma.

The best medium for culture of Bordetella pertussis is: a Regan-Lowe agar b cystine blood agar c Martin Lewis agar d Ashdown agar

a Regan-Lowe agar a Regan-Lowe agar is an enriched and selective medium for the isolation of B pertussis. Cephalexin is added to inhibit nasopharyngeal flora. It provides better isolation of B pertussis than Bordet-Gengou medium.

Which of the following media can be used to culture Campylobacter jejuni? a Skirrow medium b CIN agar c anaerobic CNA agar d bismuth sulfite

a Skirrow medium a Skirrow medium is an enriched selective blood agar medium used for the isolation of Campylobacter from specimens with mixed flora. CIN and bismuth sulfite agars are selective and differential for Yersinia enterocolitica and Salmonella, respectively. CNA agar is selective for gram- positive organisms.

The causative agent of cysticercosis is: a Taenia solium b Taenia saginata c Ascaris lumbricoides d Trichuris trichiura

a Taenia solium a Humans may become infected with Taenia solium by either ingesting the larval form or ova. If ova are ingested the parasite cannot complete the life cycle, and cysticerci encyst in various tissues including the brain.

Multifocal brain lesion in AIDS patients is commonly caused by: a Toxoplasma gondii b Pneumocystis jiroveci c Cryptosporidium parvum d Ciardia lamblia

a Toxoplasma gondii a The most common cause of ring- enhancing brain lesions in a patient with HIV/AIDS is Toxoplasma gondii.

Appropriate culture requirements for a specimen from a patient suspected of having tularemia include: a a media with cysteine such as buffered charcoal yeast extract agar b colistin nalidixic acid agar c Mueller-Hinton agar with 5% sheep blood agar d Regan-Lowe media

a a media with cysteine such as buffered charcoal yeast extract agar a Francisella tularensis is the causative agent of tularemia. It has a specific growth requirement for cysteine.

Acceptable specimens for culture of anaerobic bacteria that cause disease include: a abscesses b gingival swabs c skin swabs d vaginal swabs

a abscesses a Anaerobes normally inhabit skin and mucous membranes as part of the normal flora. Distractors b, c, and d are virtually always unacceptable for anaerobic culture, because they normally contain anaerobic organisms. It is difficult to interpret culture results from these specimens and distinguish between pathogens and normal flora.

Gram-positive cocci in chains are seen on a Gram stain from a blood culture. The organism grows as a beta-hemolytic colony. Further tests that could be performed include. a bile esculin, PYR, bacitracin, and hippurate b catalase and coagulase c oxidase and deoxyribonuclease d Voges-Proskauer and methyl red

a bile esculin, PYR, bacitracin, and hippurate a Bile esculin, PYR, bacitracin and hippurate are biochemicals/tests used in the presumptive or definitive identification of beta-hemolytic streptococci such as S pyogenes, S agalactiae and Enterococcus.

Biochemical reactions of an organism are consistent with Salmonella. A suspension is tested in polyvalent antiserum A through G and Vi antiserum. There is agglutination in the Vi antiserum only. What should be done next? a boil suspension of the organism for 10 minutes to inactivate the Vi antigen b test organism with individual antisera for agglutination c report "no Salmonella isolated" d repeat biochemical identification of the organism

a boil suspension of the organism for 10 minutes to inactivate the Vi antigen a If the Vi antigen is present, it will not permit agglutination of the polyvalent antisera. The Vi antigen is heat labile, so boiling will remove it and appropriate agglutination can take place.

Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further tests should include: a catalase production and coagulase test b bacitracin susceptibility and serological typing c oxidase and deoxyribonuclease reactions d Voges-Proskauer and methyl red reactions

a catalase production and coagulase test a The Gram stain and culture growth describe a Staphylococcus species. Catalase production confirms that the organism belonged to the genus Staphylococcus and coagulase is used to differentiate S aureus from coagulase-negative staphylococci.

Which type of microscope would be most useful in examining viruses and the structure of microbial cells? a electron b phase-contrast c dark-field d bright-fleld

a electron a Due to the small size of viruses, they are not visible using light microscopy. Electron microscopy is used to visualize viruses and the internal structure of microorganisms.

Which of the following is the most appropriate specimen source and primary media battery? a endocervical-chocolate, Martin Lewis b sputum-sheep blood, Thayer-Martin, KV-laked blood c CSF-Columbia CNA, MacConkey d urine-sheep blood, chocolate, Columbia CNA

a endocervical-chocolate, Martin Lewis a Chocolate agar and chocolate agar-based selective media (Martin Lewis) are routinely used for the recovery of Neisseria gonorrhoeae from genital specimens. Sputum and urine specimens are routinely processed using a general purpose media (blood agar) and a selective agar (EMB or MacConkey). In addition chocolate agar is routinely included to enhance recovery of fastidious organisms such as H influenzae. CSF is routinely processed using blood and chocolate agars.

An organism has been identified as a member of the fluorescent group of Pseudomonas. Which of the following sets of tests should be used to determine the species of the organism? a growth at 42°C, pyocyanin production, gelatinase production b pyocyanin production, gelatinase production, OF glucose c growth at 37°C, pyocyanin production, OF glucose d gelatinase production, growth at 52°C, H2S

a growth at 42°C, pyocyanin production, gelatinase production a Growth at 42°C and pyocyanin production are classic tests for the identification of Pseudomonas aeruginosa. Gelatin hydrolysis separates Pseudomonas putida (negative) from Pseudomonas fluorescence (positive).

A beta-hemolytic streptococcus that has been isolated from an ear culture grows up to the edge of a 0.04 unit bacitracin disk. Which of the following tests would help to determine if the organism is Enterococcus? a growth in 6.5% NaCl broth b growth in the presence of penicillin c optochin susceptibility d fermentation of 10% lactose

a growth in 6.5% NaCl broth a Of the biochemicals listed, only growth in 6.5% NaCl will aid in the identification of Enterococcus, which has the ability to grow in the presence of high salt concentrations.

A first morning sputum is received for culture of acid-fast bacilli. It is digested and concentrated by the N-acetyl-L-cysteine alkali method. Two Sabouraud dextrose slants are incubated in the dark at 35°C with 5%-10% C02. The smears reveal acid-fast bacilli, but the slants show no growti after 8 weeks. The explanation is: a improper media used b incorrect concentration procedure used c improper specimen submitted d exposure to C02 prevents growth

a improper media used a Sabouraud dextrose is fungal media; mycobacterial media should have been inoculated.

A urine specimen was submitted for isolation of cytomegalovirus (CMV). The urine was inoculated into human fibroblast tissue culture tubes. After 72 hours, no cytopathic effect was observed in the culture tubes. The most appropriate course of action is to: a incubate the culture tubes for 2-3 weeks longer b request a fecal specimen as urine is inappropriate c repeat the test using monkey kidney cell culture tubes d request CMV serology as CMV cannot be isolated

a incubate the culture tubes for 2-3 weeks longer a Cytomegalovirus is a slow-growing herpesvirus, and may require up to 3 weeks to grow in conventional viral culture.

AFB smears of a lymph node biopsy from a child are positive. At the end of 8 weeks, the AFB cultures are no growth. To enhance the possibility of recovery of the causative organism, the technologist should: a incubate the cultures an additional 4 weeks b add mycobactin J to the media c transfer the cultures to a 30°C incubator d subculture the liquid culture to chocolate agar

a incubate the cultures an additional 4 weeks a Mycobacterium malmoense requires up to Y 12 weeks for growth.

In processing clinical specimens and fungal isolates, laboratory workers may contract systemic fungal infections through: a inhalation b ingestion c skin contact d insect vector

a inhalation a Inhalation is a common mode of transmission for fungal spores. Specimens for fungal culture should be processed in a biological safety cabinet to minimize the potential for aerosol spread.

In order to isolate Campylobacter coli/jejuni, the fecal specimen should be: a inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42°C b stored in tryptic soy broth before plating to ensure growth of the organism c inoculated onto selective plating media and incubated at both 35°C and at room temperature d incubated at 35°C for 2 hours in Cary-Blair media before inoculating onto selective plating media

a inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42°C a Campylobacter coli/jejuni require a microaerophilic atmosphere for optimal recovery. The use of selective media is recommended for recovery from fecal specimens. Selective media for Campylobacter contains antibiotics to inhibit the growth of enteric gram-negative flora. Unlike other enteric pathogens, C coli/jejuni grow well at 42°C.

Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by vhich of the following procedures? a latex antigen typing b growth in 6.5% NaCl broth c growth on bile esculin medium d bacitracin susceptibility

a latex antigen typing a Growth in 6.5% NaCl, growth in bile esculin medium and susceptibility are not used in the routine identification of Streptococcus agalactiae. Polysaccharide typing for group B antigen is routinely used for identification of S agalactiae.

The major features by which molds are routinely identified are: a macroscopic characteristics and microscopic morphology b biochemical reactions and microscopic morphology c macroscopic characteristics and selective media d specialized sexual reproductive structures

a macroscopic characteristics and microscopic morphology a Macroscopic characteristics and microscopic morphology are observations used for the routine identification of molds.

The lowest concentration of antibiotic that inhibits growth of a test that inhibits growth of a test organism is the: a minimum inhibitory concentration b serum inhibitory concentration c minimum bactericidal titer d maximum inhibitory titer

a minimum inhibitory concentration a The MIC is a basic laboratory measurement of the activity of an antibiotic against an organism. It is the lowest concentration of antibiotic that inhibits visible growth of the organism. It does not represent the concentration of antibiotic that is lethal to the organism.

Respiratory syncytial virus is best isolated using a(n): a nasopharyngeal aspirate b cough plate c expectorated sputum d throat swab

a nasopharyngeal aspirate a Respiratory syncytial virus (RSV) infected the ciliated respiratory epithelium of the upper respiratory tract. A nasopharyngeal swab or aspirate is the optimal specimen for RSV recovery.

Examination of a fungal culture from a bronchial washing reveals white, cottony aerial mycelium. A tease preparation in lactophenol cotton blue shows the structures shown in the image: (IMAGE) The most rapid test for definitive identification is: a nucleic acid probe b animal inoculation c exoantigen test d slide culture

a nucleic acid probe a Nucleic acid probe test specific for only Coccidioides immitis can be completed in <4 hours.

Which one of the following results is typical of Campylobacter jejuni: a optimal growth at 42°C b oxidase negative c catalase negative d nonmotile

a optimal growth at 42°C a Campylobacter jejuni will grow at 37°C, but prefers 42°C. It is oxidase and catalase positive and motile.

Haemophilus influenzae is most likely considered normal indigenous flora in the* a oropharynx b female genital tract c large intestine d small intestine

a oropharynx a Haemophilus influenzae is indigenous flora of the upper respiratory tract.

After 24 hours a blood culture from a newborn grows catalase-negative, gram-positive cocci. The acterial colonies are small, translucent and beta-hemolytic on a blood agar plate. Biochemical test results of a pure culture are: bacitracin: resistant CAMP reaction: positive bile esculin: not hydrolyzed 6.5% NaCi broth: no growth Assuming that all controls react properly and reactions are verified, the next step would be to: a perform a Streptococcus group typing b i eport the organism as Streptococcus pneumoniae c report the organism as Staphylococcus aureus d report the organism as Staphylococcus epidermidis

a perform a Streptococcus group typing a The colony description and biochemical results presented describe Streptococcus agalactiae. The identification of this organism is confirmed by streptococcus antigen typing.

Mycobacteria that produce pigment only after exposure to light are classified as: a photochromogens b scotochromogens c rapid growers d nonchromogens

a photochromogens a Photochromogens produce nonpigmented colonies only when grown in darkness, but pigmented colonies after exposure to light.

Which characteristic best differentiates Acinetohacter species from Moraxella species? a production of indophenol oxidase b growth on MacConkey agar c motility d susceptibility to penicillin

a production of indophenol oxidase a Both Acinetobacter and Moraxella display resistance to penicillin, and some species grow on MacConkey agar. Acinetobacter are oxidase negative, and Moraxella are oxidase positive.

An outbreak of Staphylococcus aureus has occurred in a hospital nursery. In order to establish the epidemiological source of the outbreak, the most commonly used typing method is: a pulsed-field gel electrophoresis b serological typing c coagulase testing d catalase testing

a pulsed-field gel electrophoresis a The most commonly used method to determine the relatedness of 2 or more bacterial strains is pulsed-field gel electrophoresis.

13 An Enterococcus isolated from multiple blood cultures in a patient endocarditis should be: a screened for high level aminoglycoside resistance b checked for tolerance c assayed for serum antimicrobial activity d tested for beta-lactamase production

a screened for high level aminoglycoside resistance a Systemic enterococcal infections, such as endocarditis, are commonly treated with a cell-wall-active agent and an aminoglycoside. These agents act synergistically to kill the organism. If the organism is resistant to one or both, there is no synergy, and the combination will fail. It is important to detect aminoglycoside and beta-lactam resistance in these cases. Enterococci have intrinsic moderate level resistance to aminoglycosides. Acquired resistance corresponds to very high MICs (greater than 500 pg/mL) for gentamicin and is termed high level resistance.

When processing throat swabs for a group A Streptococcus culture, the medium of choice is: a sheep blood agar b rabbit blood agar c human blood agar d horse blood agar

a sheep blood agar a Sheep blood agar is preferred because clear-cut patterns of hemolysis are obtained.

Anaerobic susceptibility testing is helpful in the management of patients with: a synovial infections b rectal abscesses c streptococcal pharyngitis d pilonidal sinuses

a synovial infections There is evidence that antimicrobial resistance among anaerobic organisms is significant, and that inappropriate therapy correlates with poor patient outcomes. Susceptibility testing is useful when anaerobes are isolated from normally sterile sites such as synovial fluid. Rectal abscesses and pilonidal sinuses are polymicrobial in nature, and often resolved by surgical management.

The susceptibility results below are reported on an Enterococcus faecalis isolated from peritoneal fluid. ampicillin: susceptible vancomycin: resistant clindamycin: susceptible levofloxacin: resistant linezolid: susceptible The physician calls questioning the results. Which of the following should have been done before the report was released? a the clindamycin result should have been removed from the report since it is inactive against Enterococcus b the ampicillin result should have been changed to resistant since the isolate is vancomycin resistant c the linezolid result should have been removed from the report since it is inactive against Enterococcus d ciprofloxacin should have been added to the report since levofloxacin was resistant

a the clindamycin result should have been removed from the report since it is inactive against Enterococcus a Enterococcus species may appear active in vitro to clindamycin, cephalosporins and trimethoprim/sulfamethoxazole but are not effective clinically and should not be reported as susceptible.

Upon review of a sputum Gram stain, the technician notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is: a the slide was inadequately decolorized with acetone/alcohol b the sputum smear was prepared too thin c the cellular components have stained as expected d the iodine was omitted from the staining procedure

a the slide was inadequately decolorized with acetone/alcohol a Problems with analysis of Gram staining generally result from errors including interpretation of the slide (smear prepared too thick), excessive heat fixing, and improper decolorization. Inadequate decolorization with acetone/alcohol results in a smear in which host cells (neutrophils and squamous cells), as well as bacteria, all appear blue.

The steam autoclave method of sterilization: a uses 15 lbs of pressure for 15 minutes b utilizes dry heat for 20 minutes c produces a maximum temperature of 100 C d requires a source of ethylene oxide

a uses 15 lbs of pressure for 15 minutes a The traditional gravity displacement steam sterilization cycle is 121°C for 15 minutes at 15 pounds per square inch. Ethylene oxide is an alternative sterilization method.

Which of the following clean catch urine culture colony counts indicates the patient likely has a urinary tract infection? a 10^1 CFU/mL b 10^3 CFU/mL c 10^5 CFU/mL d no growth

b 10^3 CFU/mL b Patients with infection often have at least 100,000 bacteria/mL of urine in the bladder. However one third of young women with symptomatic cystitis have less than 100,000 bacteria/mL of urine. The Infectious Disease Society of America consensus definition of cystitis is greater than or equal to 1,000 CFU/mL of a uropathogen.

The presence of 20% bile in agar will allow growth of: a Fusobacterium necrophorum b Bacteroides ovatus c Prevotella melaninogenica d Porphyromonas gingivalis

b Bacteroides ovatus b Bile tolerant Bacteroides species will grow on agar with 20% bile (BBE agar), while Fusobacterium, Prevotella, and Porphyromonas are sensitive to 20% bile and will not grow on BBE agar. This reinforces the usefulness of bile esculin agar for differentiation of anaerobic gram-negative bacilli.

A Campylobacter pecies isolated from a stool culture gives the following biochemical reactions: naidixk: acid: cephatothm hippurate hydrolysis: oxidase, cataiase susceptible resistant positive positive positive This biochemical profile is consistent with: a Campylobacter fetus b Campylobacter jejuni c Campylobacter coli d Campylobacter laridis

b Campylobacter jejuni b Campylobacter jejuni and C coli are closely only related and both are pathogens. The test that differentiates the two is hippurate hydrolysis.

A 29-year-old man is seen for recurrence of a purulent urethral discharge 10 days after the successful treatment of culture proven gonorrhea. The most likely etiology of his urethritis is: a Mycoplasma hominis b Chlamydia trachomatis c Trichomonas vaginalis d Neisseria gonorrhoeae

b Chlamydia trachomatis b Up to 1/3 of patients with Neisseria gonorrhoeae infection are also co¬infected with Chlamydia trachomatis. Patients with identified infection with one organism are usually treated for both infections.

A genus that is found in soil and water and causes infections in immunocompromised patients has the following characteristics: sheep blood agar: violet pigment MacConkey agar: growth 42°C incubation: growth oxidase: positive OF glucose: fermenter indole: negative The genus is: a Campylobacter b Chromobacterium c Aeromonas d Serratia

b Chromobacterium b The violet pigment on sheep blood agar is a characteristic for the genus Chromobacterium. Serratia is oxidase negative, and Campylobacter does not produce a pigment and does not grow on MacConkey agar.

An anaerobic, spore-forming, nonmotile, gram-positive bacillus isolated from a foot wound is most likely; a Actinomyces israelii b Clostridium perfringens c Bacillus subtilis d Eubacterium lentum

b Clostridium perfringens b Actinomyces and Eubacterium are anaerobic gram-positive bacilli that do not form spores; Bacillus is not an anaerobic organism. Clostridium perfringens is a spore- forming anaerobe organism.

An anaerobic gram-positive bacilli with subterminal spores was isolated from a peritoneal abscess.The most likely identification of this organism is: a Bacillus cereus b Clostridium septicum c Eubacterium lentum d Bifidobacterium dentium

b Clostridium septicum b Bacillus cereus is not an anaerobic organism; Eubacterium and Bifidobacterium are anaerobic gram-positive bacilli that do not form spores. Clostridium septicum forms subterminal spores.

A fecal specimen, inoculated to xylose lysine deoxycholate (XLD) and Hektoen enteric (HE) M . produced colonies with black centers. Additional testing results are as follows: Biochemical screen Result Serological test Result glucose positive polyvalent no agglutination H2S positive group A no agglutination lysine decarboxylase positive group B| no agglutination urea negative group C no agglutination ONPG negative group D no agglutination indole positive group V, no agglutination The most probable identification is: a Salmonella enterica b Edwardsiella tarda c Proteus mirabilis d Shigella sonnei

b Edwardsiella tarda b Shigella is H2S negative, while Salmonella, Edwardsiella and Proteus are H2S positive. Proteus mirabilis is indole negative, so a lack of agglutination with Salmonella antisera indicates the presence of Edwardsiella.

A child was bitten on the arm by her sibling and the resulting wound grew a slender gram-negative bacilli that has the following characteristics: growth on SBA: colonies that "pit" the agar colonies odor: like bleach catalase: negative oxidase: positive TSI: no growth The identification of this organism is: a Moraxella catarrhalis b Eikenella corrodens c Kingella kingae d Legionella pneumophila

b Eikenella corrodens b "Pitting the agar" and the bleach smell of the colonies are hallmark characteristics of Eikenella corrodens.

Infection of the urinary tract is most frequently associated with: a Staphylococcus aureus b Escherichia coli c Enterococcus faecalis d Serratia marcescens

b Escherichia coli b >80% of uncomplicated UTIs are caused by E coli.

Which of the following organisms can grow in the small bowel and cause diarrhea in children traveler's diarrhea, or a severe cholera-like syndrome through the production of enterotoxms. a Yersinia enterocolitica b Escherichia coli c Salmonella typhi d Shigella dysenteriae

b Escherichia coli b E coli can produces several different types of toxins that result in different gastroenteritis manifestations.

A 4-year-old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is: a Listeria monocytogenes b Haemophilus influenzae c Streptococcus agalactiae d Neisseria meningitidis

b Haemophilus influenzae b Haemophilus influenzae was previously the most common cause of bacterial meningitis in young children. However, the Haemophilus influenzae type B vaccine has been in use for several years, resulting in a low incidence of H influenzae causing meningitis. This patient has not had most childhood vaccinations, so he is susceptible to H influenzae.

A small, gram-negative bacillus is isolated from an eye culture. It grows only on chocolate agar and is oxidase-variable. The most likely organism is: a Acinetobacter Iwoffii b Haemophilus influenzae c Stenotrophomonas maltophilia d Pseudomonas aeruginosa

b Haemophilus influenzae b Growth only on chocolate agar is typical for Haemophilus influenzae, which is a gram- negative coccobacillus that causes upper respiratory infections.

A cerebrospinal fluid has been inoculated onto sheep blood and chocolate agar plates and into a tube of trypticase soy broth. All media were incubated in a non atmospheric 5%C02. Which of the following organisms would usually be isolated by this procedure? a Francisella tularensis b Haemophilus influenzae c Bordetella pertussis d Bacteroides fragilis

b Haemophilus influenzae b Haemophilus influenzae is recovered on chocolate agar. Francisella and Bordetella pertussis are fastidious and require special media for growth. Bacteroides is an anaerobe that will not grow aerobically.

A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood agar. The isolate grows readily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results: ONPG: + indole: glucose: + oxidase: citrate: + VP: + The organism is most likely: a Edwardsiella tarda b Klebsiella pneumoniae c Escherichia coli d Proteus vulgaris

b Klebsiella pneumoniae b Klebsiella is the only distractor that is VP positive, and the other biochemical reactions are typical for K pneumoniae.

A vaginal/rectal swab is collected from a pregnant patient to screen for group B Streptococcus colonization. What is the best medium to use for specimen inoculation? a blood agar b LIM broth c CNA agar d thioglycollate broth

b LIM broth b Detection of group B Streptococcus (GBS) in the genital and gastrointestinal tracts of pregnant women can identify infants at risk for GBS infection. The CDC currently recommends the collection of vaginal and rectal swabs or a single swab inserted first into the vagina and then the rectum at 35-37 weeks gestation. The swab(s) should be inoculated into a selective broth medium such as LIM broth (Todd-Hewitt broth with colistin and nalidixic acid). The use of vaginal/rectal swabs and selective broth medium greatly increases the recovery of GBS.

Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar base media? a Lowenstein-Jensen, American Thoracic Society (ATS), Middlebrook 7H11 b Lowenstein-Jensen, Middlebrook 7H11, Lowenstein-Jensen Gruft c Middlebrook 7H10, Petragnani, Lowenstein-Jensen d Middlebrook 7H10, Middlebrook 7H11, Mitchison 7H11

b Lowenstein-Jensen, Middlebrook 7H11, Lowenstein-Jensen Gruft b Lowenstein-Jensen is an egg-based medium, 7H11 is an agar-based medium, and Lowenstein-Jensen Gruft is a selective egg- based medium.

A neonatal blood culture collected through a catheter grows a small yeast. Microscopically, the yeast appear round at one end, with a budlike structure on a broad base at the other end. Growth is enhanced around olive oil-saturated discs. The organism isolated is: a Candida tropicalis b Malassezia furfur c Candida lipolytica d Malassezia pachydermatis

b Malassezia furfur b Malassezia furfur causes catheter-related only sepsis, requires lipids for growth, and is a small yeast with a wide bud.

A light yellow colony from a skin lesion grew aerobically and tested as catalase positive and coagulase negative. The organism gram stained as positive cocci in clusters. The organism was modified oxidase positive, bacitracin (0.04U) susceptible and resistant to lysostaphin. What is the identification of this organism? a Staphylococcus aureus b Micrococcus luteus c Staphylococcus epidermidis d Peptostreptococcus anaerobius

b Micrococcus luteus b Micrococcus is modified oxidase positive, bacitracin (0.04U) susceptible and resistant to lysostaphin.

A Gram stain performed on a sputum specimen revealed gram-negative diplococci within PMNs. Oxidase testing is positive and carbohydrate degradation tests are inert. The organism is: a Neisseria lactamica b Moraxella catarrhalis c Neisseria meningitidis d Neisseria sicca

b Moraxella catarrhalis b The Neisseria species listed all ferment several carbohydrates, Moraxella catarrhalis is biochemically inert and does not ferment carbohydrates.

A man presents with pain on urination and urethral discharge. A Gram stain of the discharge is seen in the image: (IMAGE) What is the most likely identification of this organism? a Acinetobacter baumannii b Neisseria gonorrhoeae c Haemophilus ducreyi d Escherichia coli

b Neisseria gonorrhoeae b Gonococcal urethritis in adult males is often diagnosed by the observation of gram-negative diplococci within or closely associated with neutrophils in smears prepared from urethral discharge. The Gram stain in males has a sensitivity of 90%-95% and a specificity of 95%-100% for diagnosing gonorrhea in symptomatic males.

A gram negative bacillus with bipolar staining was isolated from a wound infection caused by a bite from a pet cat. The following characteristic reactions were seen: oxtdase positive glucose OF: fermentative cataiase positive motility: negative MacConfcey agar no growth which of the following is the most likely organism? a Pseudomonas aeruginosa b Pasteurella multocida c Aeromonas hydrophila d Vtbno cholerae

b Pasteurella multocida b Pasteurella multocida does not grow on MacConkey agar, and is associated with wounds resulting from dog and cat bites. Vibrio cholerae is motile and Pseudomonas and Aeromonas grow on MacConkey.

>100,000 CFU/mL of a gram-negative bacilli were isolated on MacConkey from a urine specimen. Biochemical results are as follows: glucose: acid, gas produced indole: negative urea: positive TDA: positive H2S: positive The organism is most likely: a Morganella morganii b Proteus mirabilis c Proteus vulgaris d Providencia stuartii

b Proteus mirabilis b Morganella and Providencia do not produce H2S; the indole reaction differentiates P mirabilis and P vulgaris.

A urine culture had the following culture results: sheep blood: Columbia CNA: MacConkey: swarming no growth >100,000 CFU/mL nonlactose-fermenter >100,000 CFU/mL nonlactose-fermenter with red pigment The isolates from MacConkey agar had the following biochemical reactions: Test Isolate 1 Isolate 2 TSI alk/acid alk/acid urea positive negative TDA positive negative H2S positive negative The organisms are most likely: a Proteus vulgaris and Enterobacter cloacae b Proteus mirabilis and Serratia marcescens c Morganella morganii and Klebsiella pneumoniae d Providencia stuartii and Serratia liquefaciens

b Proteus mirabilis and Serratia marcescens b Serratia can produce a red pigment; Proteus mirabilis swarms, is TDA positive and produces H2S.

An isolate fiom a stool culture gives the following growth characteristics and biochemical reactions: MacConkey agar: colorless colonies Hektoen agar: yellow-orange colonies TSI: acid slant/acid butt, no gas, no H2S urea: positive These scieening reactions are consistent with which of the following enteric pathogens? a Yersinia enterocolitica b Shigella sonnei c Vibrio parahaemolyticus d Campylobacter jejuni

b Shigella sonnei b Shigella has colorless colonies on both Mac Con key and Hektoen agars. Yersinia is lactose negative, but Hektoen agar (has both lactose and sucrose) produces yellow colonies from the fermentation of sucrose. V parahaemolyticus needs at least 1% NaCl to grow and Campylobacter does not grow on MacConkey or Hektoen agars.

A mold grown at 25°C exhibited delicate septate hyaline hyphae and many conidiophores extending at right angles from the hyphae. Oval, 2-5 pm conidia were formed at the end of the conidiophores giving a flowerlike appearance. In some areas "sleeves" of spores could be found along the hyphae as well. A 37 C culture of this organism produced small, cigar-shaped yeast cells. This organism is most likely: a Histoplasma capsulatum b Sporothrix schenckii c Blastomyces dermatitidis d Acremonium falciforme

b Sporothrix schenckii b The characteristics listed define Sporothrix and differentiate it from other dimorphic fungi.

Production of beta-lactamase is inducible in which of the following: a Haemophilus influenzae b Staphylococcus aureus c Cory neb acterium diphtheriae d Streptococcus pyogenes

b Staphylococcus aureus b Some bacteria such as Enterococcus sp, H influenzae and Neisseria gonorrhoeae continually produce beta-lactamase. S aureus produces beta-lactamase only after exposure 70 to an inducing agent (such as penicillin). C diphtheriae and S pyogenes do not produce beta-lactamase.

Which of the following characteristics best distinguishes Mycobacterium scrofulaceum from Mycobacterium gordonae? a iron uptake b Tween® hydrolysis c good growth at 25°C d niacin production

b Tween® hydrolysis b Tween® hydrolysis differentiates Mycobacterium gordonae (Tween® positive) from M scrofulaceum

Which of the 2 different antimicrobial agents listed below are commonly used and may result m synergistic action in the treatment of endocarditis caused by Enterococcus faecahs? a an aminoglycoside and a macrolide b a penicillin derivative and an aminoglycoside c a cell membrane active agent and nalidixic acid d a macrolide and a penicillin derivative

b a penicillin derivative and an aminoglycoside b Enterococcus species are relatively resistant to beta-lactam agents and aminoglycosides. Combination therapy with a beta-lactam agent or vancomycin and an aminoglycoside provide a synergistic combination to effectively treat enterococcal infections.

A pregnant patient is screened at 36 weeks gestation for group B Streptococcus (GBS). A vaginal swab is collected and cultured in Todd-Hewitt broth with 8 pg gentamicin/mL and 15 pg nalidixic acid/mL. The broth is subcultured onto sheep blood agar after 24 hours of incubation. No GBS are seen on the subculture and the results are reported as negative. The patient later goes on to deliver an infant with early onset GBS disease. What is the most likely reason for the negative GBS culture? a the patient was screened to early since screening after 38 weeks is recommended b a vaginal swab was collected instead of a vaginal/rectal swab c the Todd-Hewitt broth used was inhibitory to the organism d the selective broth was incubated only 24 hours before subculture

b a vaginal swab was collected instead of a vaginal/rectal swab b Group B Streptococcus (GBS) colonizes only both the genital and gastrointestinal tracts of pregnant women. Collection of a vaginal and rectal specimen is recommended by the CDC to maximize GBS detection in this population. Patients should be screened at 35-37 weeks gestation. In addition selective broth culture is recommended (Todd-Hewitt broth with antibiotics) although other selective media are also available. When selective broth culture is used it should be incubated for 18-24 hours prior to subculture onto blood agar.

An aspirate of a deep wound was plated on blood agar plates aerobically and anaerobically. At 24 hours there was growth on the anaerobic plate only. The next step in the evaluation of this culture is to: a reincubate for another 24 hours b begin organism identification c issue the final report d set up a Bauer-Kirby sensitivity

b begin organism identification b A probable anaerobe is the only organism growing so the microbiologist can proceed with identification.

The ONPG test allows organisms to be classified as a lactose fermenter by testing for following? a permease b beta-galactosidase c beta-lactamase d phosphatase

b beta-galactosidase b Through the action of the enzyme beta- galactosidase, ONPG cleaves into galactose and o-nitrophenol (a yellow compound).

A penicillin-resistant Neisseria gonorrhoeae produces: a alpha-hemolysin b beta-lactamase c enterotoxin d coagulase

b beta-lactamase b Antimicrobial resistance in Neisseria gonorrhoeae is widespread. The production of beta-lactamase (penicillinase) breaks open the beta lactam ring of penicillin, destroying its activity. Thus, Ngonorrhoeae that produce beta lactamase are resistant to penicillin.

Which species of Mycobacterium includes a BCG strain used for vaccination against tuberculosis? a tuberculosis b bovis c kansasii d fortuitum/chelonae complex

b bovis b Mycobacterium tuberculosis can remain viable but dormant in macrophages for many years.

A smear of skin tissue reveals fluorescent septate hyphae. The smear was prepared using: a acridine orange b calcofluor white c auramine rhodamine d periodic acid-Schiff

b calcofluor white b Calcofluor white binds to cellulose and chitin present in fungal cell walls.

An organism previously thought to be nonpathogenic, Moraxella catarrhalis, is now known to be associated with opportunistic respiratory infection and nosocomial transmission. Characteristici dentification criteria include: a oxidase negative b carbohydrates negative (asaccharolytic) c beta-lactamase negative d gram-negative bacilli

b carbohydrates negative (asaccharolytic) b Moraxella catarrhalis is an oxidase- positive gram-negative diplococcus that is usually beta-lactamase positive. It does not ferment carbohydrates.

A patient has a suspected diagnosis of subacute bacterial endocarditis. His blood cultures grow non-spore-forming pleomorphic gram-positive bacilli in the anaerobic bottle. What test(s) will give a presumptive identification of this microorganism? a beta-hemolysis and oxidase b catalase and spot indole c esculin hydrolysis d hydrolysis of gelatin

b catalase and spot indole b Propionibacterium acnes is part of the normal flora on the skin and is a common blood culture contaminant. The Gram stain given is typical for P acnes, and it is catalase and indole positive.

The best method to demonstrate the ova of Enterobius vermicularis is. a acid-ether concentration b cellophane tape preparation c formalin-ether concentration d zinc sulfate flotation

b cellophane tape preparation b The ova of Enterobius vermicularis cannot be demonstrated in a routine ova and parasite examination. The adult female Enterobius worm migrates out of the anus, and lays her eggs in the perianal folds. A scotch tape preparation of the skin of the perianal folds is used to collect ova.

Characteristics of the genus Capnocytophaga include: a grows in ambient air b colonies are large and spreading after 2-4 day c considered "nonfermenter" d gram-positive bacillus

b colonies are large and spreading after 2-4 day b Capnocytophaga requires increased C02, ferments glucose, sucrose, and lactose, and is a gram-negative bacillus. Capnocytophaga produces characteristic spreading colonies.

In the disk diffusion method of determining antibiotic susceptibility, the size of the inhibition zone used to indicate susceptibility has been determined by: a testing 30 strains of 1 genus of bacteria b correlating the zone size with minimum inhibitory concentrations c correlating the zone size with minimum bactericidal concentrations d correlating the zone size with the antibiotic content of the disk

b correlating the zone size with minimum inhibitory concentrations b The zone size observed has no meaning in and of itself. Interpretive standards are derived from a correlation between zone sizes and minimum inhibitory concentrations. Usually a large number of organisms from a given species or group (eg, Enterobacteriaceae) are tested.

An antibiotic used to suppress or kill contaminating fungi in media is: a penicillin b cycloheximide c streptomycin d amphotericin B

b cycloheximide b Cyclohexamide, which inhibits protein synthesis, is the common agent used in Mycosel ' or mycobiotic agar to inhibit faster-growing saprophytic fungi. Penicillin and streptomycin do not inhibit fungi. Amphotericin B is not routinely used as an additive in fungal media.

The best medium for culture of Francisella tularensis is: a Bordet-Gengou medium b cystine glucose blood agar c Loeffler medium d charcoal selective medium

b cystine glucose blood agar b Francisella tularensis is fastidious and not readily recovered in culture. Cysteine blood glucose agar is an enriched medium with beef heart infusion, peptones, glucose and rabbit blood. It also includes cystine, which is required by F tularensis for growth.

In disk diffusion susceptibility testing, as an antimicrobial agent diffuses away from the concentration of antibiotic is: a increased b decreased c unchanged d inoculum dependent

b decreased b The amount of antibiotic used in disk diffusion susceptibility testing is standardized and constant. Once the disk is placed on the inoculated plate and makes contact with the agar, the antibiotic in the disk begins to diffuse out. As it diffuses into the media, the concentration of antibiotic gets lower the further it diffuses from the disk.

A test is performed on an isolate of Staphylococcus aureus to determine inducible clindamycin resistance: (IMAGE) Based on the result seen in the image how should the erythromycin and clindamycin be reported? a erythromycin: resistant; clindamycin: resistant b erythromycin: resistant; clindamycin: susceptible c erythromycin: susceptible; clindamycin: resistant d erythromycin: susceptible; clindamycin: susceptible

b erythromycin: resistant; clindamycin: susceptible b The image displays a negative D test result. There is no flattening of the zone of inhibition around the clindamycin disk adjacent to the erythromycin disk. Thus, there is no inducible clindamycin resistance, and the isolate is reported as clindamycin- susceptible, while the erythromycin is reported as resistant.

After satisfactory performance of daily disk diffusion susceptibility quality control is documented, the frequency of quality control can be reduced to: a twice a week b every week c every other week d every month

b every week b Daily disk diffusion quality control can be converted to weekly testing when 30 days of consecutive testing demonstrates no more than 3 antibiotic/organism combinations outside of the acceptable limits.

A liquid fecal specimen from a three-month-old infant is submitted for microbiological examination. In addition to culture on routine media for Salmonella and Shigeli. this specimen should be routinely: a examined for the presence of Entamoeba hartmanni b examined for the presence of Campylobacter sp c screened for the detection of enterotoxigenic Escherichia coli d placed in thioglycollate broth to detect Clostridium botulinum

b examined for the presence of Campylobacter sp b Campylobacter continues to be the most common enteric pathogen isolated from patients with diarrhea. Routinely fecal specimens should be cultured for Salmonella, Shigella and Campylobacter. Fecal specimens are not routinely cultured for enterotoxigenic E coli or C botulinum. E hartmanni is a onpathogenic parasite and does not cause diarrhea.

Which 2 diseases are usually preceded by infection with beta-hemolytic streptococci? a rheumatic fever, undulant fever b glomerulonephritis, rheumatic fever c rheumatic fever, tularemia d glomerulonephritis, undulant fever

b glomerulonephritis, rheumatic fever b Noninfectious sequelae associated with infection with Streptococcus pyogenes are glomerulonephritis and rheumatic fever.

The advantage of thick blood smears for malarial parasites is to. a improve staining of the organisms b improve detection of the organisms c remove RBC artifacts d remove platelets

b improve detection of the organisms b The increased amount of blood placed on the slide of a thick smear for blood parasites improves the sensitivity of the smear. Thick smears should be performed on all requests for blood parasites.

Blood cultures from a case of suspected leptospiremia should be drawn: a between 10 PM and 2 AM b in the first 7-10 days of infection c during febrile periods, late in the course of the disease d after the first 10 days of illness

b in the first 7-10 days of infection b Leptospira organisms can be readily detected by culturing blood during the first week of illness. After this time the organisms disappear from blood and are excreted from the urine for up to 1 month.

Virus transport medium containing penicillin, gentamicin and amphotericin is used to collect and transport specimens for virus culture because this medium: a enables rapid viral growth during the transport time b inhibits bacterial and fungal growth c destroys nonpathogenic viruses d inhibits complement-fixing antibodies

b inhibits bacterial and fungal growth b antibiotics and antifungal agents are added to viral transport medium to inhibit the growth of bacteria and fungus.

Which of the following indicates the presence of a viral infection in tissue smears or biopsies? a cytopathic effect b intranuclear inclusions c cell lysis d mononuclear inflammatory cells

b intranuclear inclusions b In tissue smears or biopsy specimens, the presence of virally infected cells is indicated by intranuclear or intracytoplasmic inclusions.

The lab has been using a latex agglutination assay to detect Clostridium difficile in stools, which identifies a nontoxin cell wall antigen. The lab is considering adoption of an ELA method that detects Clostridium difficile toxin A. Which of the following would provide the best compariso. a latex agglutination vs culture on cycloserine cefoxitin-egg-fructose agar b latex agglutination vs EIA vs cell culture cytotoxin assay c EIA vs culture on cycloserine cefoxitin-egg-fructose agar d EIA vs cell culture cytotoxin assay

b latex agglutination vs EIA vs cell culture cytotoxin assay b One must compare the sensitivity of o^y latex agglutination that is currently used in the laboratory with the proposed EIA method for toxin A detection. The cell culture cytotoxin assay should be included as a gold standard for toxin detection.

When evaluating a new susceptibility testing system, if the new system characterizes a susceptible isolate as resistant, this is termed a: a very major error b major error c minor error d acceptable error

b major error b When evaluating susceptibility testing systems the following conventions are used: a very major error occurs when the system characterizes a resistant isolate as susceptible; a major error occurs when the system characterizes a susceptible isolate as resistant; and a minor error occurs when the system characterizes a susceptible or resistant isolate as intermediate, or an intermediate isolates as susceptible or resistant.

Assuming the agent isolated from a patient's spinal fluid produces a positive oxidase test, the most likely diagnosis is: a tuberculous meningitis b meningococcal meningitis c viral meningitis d pneumococcal meningitis

b meningococcal meningitis b Of the possible types of meningitis listed, only Neisseria meningitidis is oxidase positive.

The best procedure to differentiate Listeria monocytogenes from Corynebacterium species is: a catalase b motility at 25°C c motility at 35°C d Gram stain

b motility at 25°C b Corynebacterium and Listeria are catalase-positive and gram-positive bacilli. Listeria demonstrates "tumbling motility that is best demonstrated following growth at 25°C. A few species of Cory neb acterium species are motile when grown at 35°C.

Shigella species characteristically are: a urease positive b nonmotile c oxidase positive d lactose fermenters

b nonmotile b The biochemical characteristic that best fits Shigella is that it is nonmotile. Shigella are urease negative and oxidase negative. Shigella are lactose nonfermenters.

A urine Gram stain shows gram-positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technician should perform a coagulase test and a/an: a polymyxin B susceptibility b novobiocin susceptibility c oxidase d beta lactamase

b novobiocin susceptibility b The organism in this urine culture is a Staphylococcus species. Coagulase will differentiate S aureus from coagulase- negative staphylococci (CNS) and novobiocin susceptibility will differentiate S saprophyticus from other CNS. S saprophyticus is a common cause of urinary tract infections in young females.

Many fungal infections are transmitted to man via inhalation of infectious structures. Which of the following is usually contracted in this manner? a Sporothrix schenckii b Trichophyton rubrum c Malassezia furfur d Histoplasma capsulatum

d Histoplasma capsulatum d Histoplasma capsulatum is most frequently transmitted by inhalation.

A 73-year-old man diagnosed as having pneumococcal meningitis is not responding to his penicillin therapy. Which of the following tests should be performed on the isolate to best determine this organism's susceptibility to penicillin? a beta-lactamase b oxacillin disk diffusion c penicillin disk diffusion d Schlichter test

b oxacillin disk diffusion b With the exception of the oxacillin disk screening test, disk diffusion is not recommended for testing S pneumoniae against beta-lactam agents. S pneumoniae does not produce beta-lactamase, so beta- lactamase testing would not be useful. The Schlichter test is not a method for determining an organisms susceptibility to a given agent.

An antibiotic that inhibits cell wall synthesis is: a chloramphenicol b penicillin c sulfamethoxazole d colistin

b penicillin b Penicillin inhibits penicillin binding proteins that are essential to peptidoglycan (cell wall) synthesis. Chloramphenicol inhibits protein synthesis, colistin increases cell membrane permeability, and sulfamethoxazole inhibits folate metabolism.

A physician calls the laboratory to verify a result of Mycobacterium tuberculosis, stating that the clinical history of the patient is not compatible with tuberculosis. On review of the patient's culture, the smear was negative and the culture became positive at 5 weeks in the broth culture. Additionally, it was determined that another patient's specimen that was processed the same day was 4+ AFB on smear and the culture was positive at 10 days for Mycobacterium tuberculosis. The lab should: a include a positive control when processing specimens b perform molecular fingerprinting on both isolates c repeat the nucleic acid probe d set up susceptibility tests

b perform molecular fingerprinting on both isolates b If the molecular fingerprint is the same, the smear-negative culture should be considered a false positive, and the laboratory should review its processing procedures.

A 21-year-old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be: a set up immediately b rejected as unacceptable c inoculated into thioglycollate broth d sent to a reference laboratory

b rejected as unacceptable b Many anaerobic bacteria are commensal flora in the oropharynx. Anaerobic bacteria do not cause pharyngitis. The most common cause of pharyngitis is Streptococcus pyogenes. Other causes include Arcanobacterium haemolyticum, Corynebacterium diphtheriae, Neisseria gonorrhoeae and viruses.

Characteristically, enterococci are: a unable to grow in 6.5% NaCl b relatively resistant to penicillin c sodium hippurate positive d bile esculin negative

b relatively resistant to penicillin b Enterococci are bile esculin-positive, hippurate-negative and have the ability to grow in 6.5% NaCl. Enterococci are relatively resistant to penicillin and require combination therapy to treat serious infections.

Quality control testing of CHROMagar™ Candida medium shows very weakly colored colonies after incubation at 25°C, ambient atmosphere for 48 hours. The technologist should: a repeat the quality control tests to verify results b repeat the quality control tests but incubate at 35°C c repeat the quality control tests using new subcultures of the quality control organisms d discard this lot of CHROMagar™ and repeat the quality control tests on a new lot number

b repeat the quality control tests but incubate at 35°C b CHROMagar™ produces the best color only development when incubated at 35°-37°C.

Upon finding the above in a fecal concentrate, the technologist should: a telephone the report of this pathogen to the physician immediately b review the fecal concentration carefully for the presence of other microorganisms that may be pathogenic c look for motile trophozoites d request a new specimen because of the presence of excessive pollen grains

b review the fecal concentration carefully for the presence of other microorganisms that may be b Entamoeba coli is a nonpathogenic protozoan. Its presence indicates the ingestion of fecally contaminated food or water and should lead to a closer review of the specimen for pathogenic parasites or the collection of additional specimens.pathogenic

An aspirated specimen of purulent material was obtained from a brain abscess. After 24 hours incubation, pinpoint colonies grew on sheep blood and small, yellowish colonies grew on chocolate. Gram stain of the organism showed gram-negative cocci. Results of carbohydrate degradation studies were as follows: glucose: acid maltose: acid sucrose: acid lactose: negative Additional testing revealed that the organism was oxidase positive and beta-galactosidase negative. The organism is most likely Neisseria: a meningitidis b sicca c lactamica d gonorrhoeae

b sicca b Neisseria sicca is the only Neisseria species of those listed that ferments glucose, maltose and sucrose.

A control strain of Clostridium should be used an anaerobe jar to assure: a that plate media is working b that an anaerobic environment is achieved c that the jar is filled with a sufficient number of plates d that the indicator strip is checked

b that an anaerobic environment is achieved b Several Clostridium species are obligate anaerobes, and will only grow in an anaerobic environment. The growth of one of these clostridium species would confirm that an anaerobic environment has been achieved in anaerobic jar.

Three sets of blood cultures were obtained from an adult patient with fever and suspected endocarditis. The aerobic bottle of one set had growth of Staphylococcus epidermidis at 5 days of incubation. This indicates that: a there was low-grade bacteremia b the organism is most likely a contaminant c the patient has a line infection d the blood culture bottles are defective

b the organism is most likely a contaminant b Coagulase-negative staphylococci are commonly associated with contaminated blood cultures; however, they are also increasing as a cause of true bacteremia. Significant bacteremia in a patient with endocarditis is usually continuous and low grade. In most cases, all blood cultures drawn will yield positive results. The facts that only 1 bottle of 1 set was positive, and that the bottle did not become positive until day 5 of incubation, indicate that this isolate is most likely a contaminant.

The proper blood-to-broth ratio for blood cultures to reduce the antibacterial effect of serum in adults is: a 1:2 b 1:3 c 1:10 d 1:30

c 1:10 c Human blood contains substances that may inhibit microbial growth. Diluting blood in culture broth reduces the concentration of these substances as well as any antibiotics that may be present. The recommended blood broth ratio is 1:5-1:10. Dilutions less than this may cause the blood to clot trapping organisms in the clot. Greater dilutions may increase the time to detection

Which of the following is the most important variable in the recovery of organisms in patients with bacteremia? a subculture of all bottles at day 5 of incubation b the volume of blood cultured c use of chlorhexadine for skin antisepsis d collection of multiple blood culture sets from a single venipuncture

b the volume of blood cultured b The volume of blood collected is the single most important variable in the recovery of organisms in patients with bloodstream infections. Since many cases of adult bacteremia are of low magnitude, there is a direct relationship between the yield of blood culture (positivity) and volume of blood collected. The collection of multiple blood culture sets from a single venipuncture is an unacceptable practice due to the potential for contamination. The practice of terminal subculture of blood culture bottles at 5 days is no longer recommended. The use of chlorhexadine for skin antisepsis does not affect organism recovery, but aids in decreasing blood culture contamination.

Which of the following factors would make an organism appear to be more resistant on a disk diffusion susceptibility test? a too little agar in the plate b too many organisms in the inoculum c the presence of 0.5% NaCl in the medium d a medium with a pH of 7.4

b too many organisms in the inoculum b To ensure the reproducibility of disk diffusion testing, the inoculum must be standardized. If the inoculum is too dense (too many organisms), zone sizes would be smaller than expected and appear falsely resistant.

When performing a Kovac indole test, the substrate must contain: a indole b tryptophan c ornithine d paradimethylaminobenzaldehyde

b tryptophan b The indole test is used for determining an organism's ability to produce indole from deamination of tryptophan by tryptophanase.

When performing a stool culture, a colony type typical of an enteric pathogen is subcultured on a blood agar plate. The resulting pure culture is screened with several tests to obtain the following results: TSI: acid butt, alkaline slant, no gas, no H2S phenylalanine deaminase: negative motility: positive serological typing: Shigella flexneri (Shigella subgroup B) The serological typing is verified with new kit and controls. The best course of action would be to: a report the organism as Shigella flexneri without further testing b verify reactivity of motility medium with positive and negative controls c verify reactivity of the TSI slants with positive and negative controls for H2S production d verify reactivity of phenylalanine d aminase with positive and negative controls

b verify reactivity of motility medium with positive and negative controls b All of the biochemical and serological reactions listed are consistent with an identification of Shigella flexneri, with the exception of motility. All Shigella are nonmotile.

A clean catch urine sample from a nursing home patient is cultured using a .001 mL loop. It grows 67 colonies of a lactose fermenter that has the following biochemical reactions: TSI: acid/acid oxidase: negative motility: positive indole: negative citrate: positive VP: positive lysine decarboxylase: negative ornithine decarboxylase: positive urea: negative What should the microbiologist report? a 670 CFU/mL Serratia marsecens sp b 6,700 CFU/mL Providencia stuartii c 67,000 CFU/mL Enterobacter cloacae d 67,000 CFU/mL Klebsiella oxytoca

c 67,000 CFU/mL Enterobacter cloacae c The correct quantitation on a urine sample is obtained by counting the colonies and multiplying them by the dilution factor, which in this case is 1000 because a .001 pL loop was used for culture. The biochemicals are characteristic of Enterobacter cloacae.

The Gram stain from a blood culture shows gram-positive cocci in chains. No growth occurs on blood agar plates incubated both aerobically and anaerobically. Additional testing should be done to detect the presence of: a Staphylococcus saprophyticus b Aerococcus urinae c Abiotrophia defectiva d Streptococcus pneumoniae

c Abiotrophia defectiva c Nutritionally deficient streptococci such as Abiotrophia do not grow on sheep blood agar without the addition of cysteine or proximity to S aureus colonies.

While swimming in a lake near his home, a young boy cut his foot, and an infection developed. The culture grew a nonfastidious gram-negative, oxidase positive, beta-hemolytic, motile bacilli that produced deoxyribonuclease. The most likely identification is: a Enterobacter cloacae b Serratia marcescens c Aeromonas hydrophila d Escherichia coli

c Aeromonas hydrophila c Enterobacteriaceae, such as E coli, Serratia and Enterobacter, are oxidase negative. The only selection that is oxidase positive is Aeromonas. It is associated with wounds contaminated with water.

Fluid from a cutaneous black lesion was submitted for routine bacterial culture. After 18 hours of incubation at 35°C there was no growth on MacConkey agar, but 3+ growth on sheep blood agar. The colonies were nonhemolytic, nonmotile, 4-5 mm in diameter and off-white with a ground glass appearance. Each colony had an irregular edge with comma-shaped outgrowths that stood up like "beaten egg whites" when gently lifted with an inoculating needle. A Gram stain of a typical colony showed large, gram-positive rectangular bacilli. The organism is most likely: a Clostridium perfringens b Aeromonas hydrophila c Bacillus anthracis d Mycobacterium marinum

c Bacillus anthracis c Bacillus anthracis are large, rectangular gram-positive bacilli that produce colonies with an irregular edge (often described as a "medusa-head" appearance) on blood agar. Colonies are nonhemolytic, catalase positive and nonmotile.

Which organism commonly causes food poisoning by consumption of foods containing excessive populations of organisms or preformed enterotoxin? a Salmonella enteritidis b Shigella sonnei c Bacillus cereus d Escherichia coli

c Bacillus cereus c Bacillus cereus is the etiologic agent of 2 distinct types of food poisoning syndromes. Spores can survive cooking and germinate. Vegetative cells multiply and produce toxin.

The Epstein-Barr virus is associated with which of the following? a chickenpox b Hodgkin lymphoma c Burkitt lymphoma d smallpox

c Burkitt lymphoma c The classic clinical syndrome associated with Epstein-Barr virus (EBV) infection is infectious mononucleosis. However, in immunocompromised patients, EBV is associated with posttransplant lymphoproliferative disorders, and malignancies such as Burkitt lymphoma.

A stool sample is sent to the laboratory for culture to rule out Clostridium difficile. What media should the microbiologist use and what is the appearance of the organisms on this media? a BBE: colonies turn black b Brucella agar: red pigmented colonies c CCFA: yellow, ground glass colonies d CNA: double zone hemolytic colonies

c CCFA: yellow, ground glass colonies c Selective media are needed to isolate Clostridium difficile from stool and CCFA is also differential—fermentation of lactose produces classic colony morphology for this organism.

The morphological characteristics of a yeast grown in rabbit plasma are shown in the image: The most likely identification of this yeast is. a Candida tropicalis b Candida krusei c Candida albicans d Candida glabr at a

c Candida albicans c Candida albicans produce tubular structure with no constrictions (germ tubes) when incubated in rabbit plasma.

Which of the following statements concerning the germ tube test is true? a using a heavy inoculum enhances the rapid production of germ tubes b germ tubes should be read after 2 hours incubation at 25°C c Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively d serum will be stable for 1 year if stored at 4°C prior to use

c Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively c Candida albicans (positive) and C tropicalis (negative) can be used as control organisms for quality control of the germ tube test.

Iodine staining of a McCoy cell monolayer culture of a cervical swab reveals a large brown intracytoplasmic inclusion. What is the most likely infecting organism? a cytomegalovirus b Ehrlichia chaffeensis c Chlamydia trachomatis d Rickettsia prowazekii

c Chlamydia trachomatis c Iodine staining can be used to detect omy the glycogen-rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

Which one of the following organisms could be used as the positive quality control test for lecithinase on egg yolk agar? a Bacteroides fragilis b Fusobacterium necrophorum c Clostridium perfringens d Clostridium sporogenes

c Clostridium perfringens Clostridium perfringens is lecithinase positive. Bacteroides, Fusobacterium and Clostridium sporogenes are lecithinase negative.

The examination of human feces is no help in the detection of- a Strongyloides stercoralis b Entamoeba histolytica c Echinococcus granulosus d Ancvlostoma duodenale

c Echinococcus granulosus c The diagnostic stages of Strongyloides, Entamoeba and Ancylostoma can be detected in the stool of infected patients. The diagnostic stage of Echinococcus granulosus is not detected in an infected patients stool.

A mycobacterial isolate that causes multiple skin nodules, grows at 30°C and requires hemin for growth is Mycobacterium: a marinum b genavense c haemophilum d xenopi

c haemophilum c Mycobacterium haemophilum grows best at 30°C, requires hemin or ferric ammonium citrate for growth, and causes subcutaneous lesions presenting as multiple skin nodules.

A iaundiced 7-year-old boy, with a history of playing in a pond in a rat-infested area, has a urine specimen submitted for a direct dark-held examination. No organisms are seen in the specimen. Which medium should be inoculated in an attempt to isolate the suspected organism? a blood cysteine dextrose b PPLO agar c Fletcher semisolid d chopped meat glucose

c Fletcher semisolid c The clinical syndrome described is most likely the icteric form of Leptospira interrogans. The most commonly used medium for culture is Fletcher semisolid agar. Cultures are incubated in the dark for up to 6 weeks at 28°-30°C and examined weekly by darkfield microscopy

An isolate from a cornea infection had the following culture results: Sabouraud dextrose: white & cottony at 2 days, rose color at 6 days slide culture: slender sickle shape macroconidia The most likely organism is : a Acremonium b Aspergillus c Fusarium d Geotrichuma

c Fusarium c Fusarium frequently cause cornea infections and have sickle-shaped macroconidia.

A thin, gram-negative bacillus with tapered ends isolated from an empyema specimen grew only on anaerobic sheep blood agar. It was found to be indole positive, lipase negative, and was inhibited by 20% bile. The most probable identification of this isolate would be: a Bacteroides distasonis b Prevotella melaninogenica c Fusobacterium nucleatum d Clostridium septicum

c Fusobacterium nucleatum c Fusobacterium nucleatum is classically only described as a long, slender, gram-negative bacillus with tapered ends. Inhibition of growth by 20% bile and a positive indole reaction narrow the selection process.

Multiple blood cultures from a patient with endocarditis grew a facultatively anaerobic, pleomorphic gram-negative bacilli with the following characteristics: hemolysis: negative MacConkey agar: no growth sheep blood agar: growth in 5%-10% CO2 chocolate agar: growth in 5%-10% CO2 catalase: negative V factor: not required X factor: not required oxidase: negative nitrate: positive, reduced to nitrites indole: negative The most likely identification is: a Brucella abortus b Actinobacillus actinomycetemcomitans c Haemophilus aphrophilus d Cardiobacterium hominis

c Haemophilus aphrophilus c Biochemicals and growth characteristics are indicative of Haemophilus aphrophilus. Brucella and Cardiobacterium are oxidase positive, and Actinobacillus are catalase positive.

A gram stain of a touch prep from a gastric biopsy shows gram-negative bacilli that are slender and curved. The most likely pathogen is. a Burkholderia cepacia b Corynebacterium urealyticum c Helicobacter pylori d Pasteurella multocida

c Helicobacter pylori c Helicobacter pylori is known to cause gastritis and is a gram-negative, curved bacillus.

Gram stain examination of a CSF specimen indicates the presence of yeast-like cells with gram- positive granular inclusions. Which of the following techniques should be used next to assist in the identification of this organism? a 10% KOH b lactophenol cotton blue c India ink d periodic acid-Schiff

c India ink c Cryptococcus may not stain well on Gram stain. Rapid identification is important when yeast is detected in CSF, the presence of capsules seen in an India ink preparation would be presumptive for C neoformans.

The best medium for culture of Mycobacterium tuberculosis is: a Bordet-Gengou agar b Loeffler medium c Lowenstein-Jensen medium d cystine blood agar

c Lowenstein-Jensen medium c Lowenstein-Jensen is an egg-based medium used to isolate AFB. The other media are not used for the isolation of AFB.

Culture of a strand of hair, that fluoresced yellow-green when examined with a Wood lamp, produced a slow-growing, flat gray colony with a salmon-pink reverse. Microscopic examination demonstrated racquet hyphae, pectinate bodies, chlamydospores, and a few abortive or bizarre¬shaped macroconidia. The most probable identification of this isolate is: a Epidermophyton floccosum b Microsporum canis c Microsporum audouinii d Trichophyton rubrum

c Microsporum audouinii c Hair that fluoresces yellow-green under a Woods lamp indicates the presence of a Microsporum species. The colony morphology and microscopic characteristics are consistent with M audouinii.

The nitrate test for mycobacteria can be performed with a reagent impregnated paper strip or by the use of standard reagents. In order to quality control the test properly, which of the following should be used for a positive control? a Mycobacterium bovis b Mycobacterium gordonae c Mycobacterium tuberculosis d Mycobacterium intracellulare

c Mycobacterium tuberculosis c Mycobacterium tuberculosis is the {LY only mycobacterium listed that is nitrate eduction positive.

A fibrous skin nodule is removed from the back of a patient from Central America. A microfilaria seen upon microscopic exam of the nodule is: a Wuchereria bancrofti b Brugia malayi c Onchocerca volvulus d Loa loa

c Onchocerca volvulus c Onchocerca volvulus is the only only microfilaria that is detected in the skin snips of patients with raised skin nodules. The microfilaria of Wuchereria, Brugia and Loa loa are found in the blood of infected patients

Which one of the following anaerobes is inhibited by sodium polyanethol sulfonate (SPS)? a Bacteroides fragilis b Propionibacterium acnes c Peptostreptococcus anaerobius d Veillonella parvula

c Peptostreptococcus anaerobius c SPS in blood culture media enhances recovery of most bacteria, including anaerobes. However, Peptostreptococcus anaerobius is inhibited by SPS.

A 44-year-old man was admitted to the hospital following a 2-week history of low-grade fever, malaise and anorexia. Examination of a Giemsa stain revealed many intraeryt rocytic parasites. Further history revealed frequent camping trips near Martha s Vineyard and Nantuc et Is and, but no travel outside the continental United States. This parasite could easily be con use wi . a Trypanosoma cruzi b Trypanosoma rhodesiense/gambiense c Plasmodium falciparum d Leishmania donovani

c Plasmodium falciparum c The patients history is suggestive of Babesia infection. Babesia microti ring forms are similar to Plasmodium falciparum. A travel history is helpful in determining the cause of infection.

A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hours, was found to fluoresce brick-red under ultraviolet light. A Gram stain of the organism revealed a coccobacillus that had the following characteristics: growth in bile: inhibited vancomycin: resistant kanamycin: resistant colistin: susceptible catalase: negative esculin hydrolysis: negative indole: negative The identification of this isolate is: a Bacteroides ovatus b Prevotella oralis c Prevotella melaninogenica d Porphyromonas asaccharolytica

c Prevotella melaninogenica c Both Prevotella and Porphyromonas colonies fluoresce brick red. Porphyromonas is susceptible to vancomycin and can be catalase positive.

Pus from a draining fistula on a foot was submitted for culture. Gross examination of the specimen revealed the presence of a small (0.8 mm in diameter), yellowish, oval granule. Direct microscopic examination of the crushed granule showed hyphae 3-4 pm in diameter and the presence of chlamydospores at the periphery. After 2 days a cottony, white mold was seen that turned gray with a gray to black reverse after a few days. When viewed microscopically, moderately large hyaline septate hyphae with long or short conidiophores, each with a single pear-shaped conidium, 5-7 x 8-10 pm, were seen. The most likely identification is: a Exophiala jeanselmei b Fonsecaea pedrosoi c Pseudallescheria boydii d Cladosporium carrionii

c Pseudallescheria boydii c microscopic characteristics differentiate Pseudallescheria boydii from the ther fungi listed.

The optochin (ethylhydrocupreine hydrochloride) disk is used for the identification of: a Haemophilus influenzae b group A beta-hemolytic streptococci c Streptococcus pneumoniae d alpha-hemolytic streptococci

c Streptococcus pneumoniae c Optochin susceptibility is used to differentiate S pneumoniae, which are susceptible, from other alpha-hemolytic streptococci, which are resistant.

Which of the following organisms is, to date, considered universally susceptible to penicillin: a Haemophilus influenzae b Neisseria gonorrhoeae c Streptococcus pyogenes d Cory neb acterium diphtheriae

c Streptococcus pyogenes c Haemophilus influenzae and Neisseria gonorrhoeae do not have predictable susceptibility to penicillin. Corynebacterium diphtheriae is not universally susceptible to penicillin. To date, no penicillin resistance has been demonstrated in Streptococcus pyogenes.

Which one of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated from a clinically significant source? a Staphylococcus aureus-clindamycin b Proteus mirabilis-gentamicin c Streptococcus pyogenes-penicillin d Escherichia coli-levofloxacin

c Streptococcus pyogenes-penicillin c Susceptibility testing should be performed when the susceptibility of the organism cannot reliably be predicted and resistance is known or suspected. Susceptibility testing of penicillins for treatment of S pyogenes does not need to be performed routinely since resistance has not been documented.

Which organism fails to grow on artificial media or in cell cultures? a Chlamydia trachomatis b Neisseria gonorrhoeae c Treponema pallidum d herpes simplex virus

c Treponema pallidum c Chlamydia trachomatis, Neisseria gonorrhoeae and herpes simplex virus can all be isolated in culture. Direct culture of Treponema pallidum on artificial media has not been achieved. Darkfield microscopy and serological techniques are used to diagnose T pallidum infection.

Darkfield microscopy is can be used to visualize: a Pseudomonas aeruginosa b Streptococcus pneumoniae c Treponema pallidum d Legionella pneumophila

c Treponema pallidum c Darkfield microscopy can be performed to visualize Treponema pallidum in genital or skin lesions. Darkfield examination allows for the visualization of Tpallidum s typical morphology and motility

Which of the following sets of organisms may exhibit a brick red fluorescence? a Porphyromonas asaccharolytica and Clostridium ramosum b Clostridium difficile and Fusobacterium sp c Veillonella parvula and Prevotella melaninogenica d Fusobacterium sp and Veillonella parvula

c Veillonella parvula and Prevotella melaninogenica c Prevotella, Porphyromonas and Veillonella produce colonies that fluoresce brick red.

One of the enterotoxins produced by enterotoxigenic Escherichia coli in traveler's diarrhea is similar to a toxin produced by: a Clostridium perfringens b Clostridium difficile c Vibrio cholerae d Yersinia enterocolitica

c Vibrio cholerae c The toxin produced by enterotoxigenic E coli is similar in action and amino acid sequence to cholera toxin.

A 4-year-old is admitted with symptoms of meningitis, and a Gram stain of the cerebrospinal fluid reveals small, pleomorphic, gram-negative coccobacilli. After 24 hours incubation at 35°C, small, moist, gray colonies, which are oxidase variable, are found on the chocolate agar plate only. Which of the following biochemical data would be consistent with this isolate? a CTA dextrose: positive CTA maltose: positive ONPG: negative b sodium hippurate hydrolysis: positive A disc: negative CAMP test: positive c X factor: no growth V factor: no growth XV factor: growth horse blood: no hemolysis d catalase: positive esculin hydrolysis: positive methyl red: positive "umbrella" motility at room temperature

c X factor: no growth V factor: no growth XV factor: growth horse blood: no hemolysis c These are classic gram stain, growth and biochemicals for Haemophilus influenzae.

An 8-year-old girl was admitted to the hospital with a three-day history of fever, abdominal pain, diarrhea, and vomiting. A stool culture grew many lactose-negative colonies that yielded the following test results: oxidase: negative TSI: acid slant/acid butt indole: negative urease: positive ornithine decarboxylase: positive sucrose: positive H^S: negative motility at 25°C: positive The most probable identification of this organism is: a Escherichia coli b Proviciencia stuartii c Yersinia enterocolitica d Edwardsiella tarda

c Yersinia enterocolitica c Edwardsiella produces H2S; E coli is indole positive; Providencia has a TSI reaction of alkaline/acid. Yersinia typically shows motility at 25°C and not 35°C.

The optimal wound specimen for culture of anaerobic organisms should be: a a swab of lesion obtained before administration of antibiotics b a swab of lesion obtained after administration of antibiotics c a syringe filled with pus, obtained before administration of antibiotics d a syringe filled with pus, obtained after administration of antibiotics

c a syringe filled with pus, obtained before administration of antibiotics c The use of swabs for collection of specimens for anaerobic culture is discouraged. Aspiration with a needle and syringe is recommended. Whenever possible cultures should be obtained before the administration of antibiotics to optimize organism recovery.

In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of staphylococcus aureus (ATCC 25923), all the disk zone sizes are too small. The most likely reason for this is that the: a Mueller-Hinton plates were poured too thin b potency of the antibiotic disks is too high c bacterial suspension was not diluted to the proper concentration d disks should have been set up on mannitol salt

c bacterial suspension was not diluted to the proper concentration c Quality control zone sizes that are too small could indicate that the organism inocdum is too high, plates were poured too thick, or that the potency of the antibiotic disks is too low.

In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic susceptibility to aminoglycosides? a incubation temperature b duration of incubation c cation content of media d depth of agar

c cation content of media c Variations in the concentrations of divalent cations primarily calcium and magnesium affect the results of aminoglycoside, tetracycline and colistin tests with P aeruginosa isolates. A cation concentration that is too high results in smaller zone sizes, and a concentration that is too low increases zone sizes.

The enterotoxin produced by certain strains of hemolytic, coagulase positive Staphylococcus aureus: a is destroyed by boiling for 15-30 minutes b is identical to the dermonecrotic toxin c causes one type of bacterial food poisoning d is highly antigenic

c causes one type of bacterial food poisoning c Staphylococcus aureus produces an enterotoxin that is associated with short- incubation food poisoning.

Which of the following combinations is useful for confirming the presence of extended spectrum beta-lactamases in E colil a ampicillin + cefepime b cefoxitin + penicillin c ceftazidime + clavulanic acid d cefpodoxime + cefotaxime

c ceftazidime + clavulanic acid c Extended spectrum beta lactamases (ESBL) are inhibited by clavulanic acid. Confirmatory tests of the presence of ESBL are based on the enhanced activity of a beta-lactam antibiotic, usually cefotaxime or ceftazidime, when it is tested with clavulanic acid compared to the activity of the beta- lactam tested alone.

First generation cephalosporins can be adequately represented by: a cefotetan b ceftriaxone c cephalothin d cefoxitin

c cephalothin c Cephalothin is a first-generation cephalosporin, cefotetan and cefoxitin are second-generation cephalosporins, and ceftriaxone is a third generation cephalosporin.

Media used to support to support growth of Legionella pneumophilia should contain which of the following additives? a X and V factors b hemin and Vitamin K c charcoal and yeast extract d dextrose and laked blood

c charcoal and yeast extract c Buffered charcoal yeast extract medium is a specialized enrichment medium for the isolation of Legionella. The nutritive base includes yeast extract. Charcoal is added to the medium as a detoxifying agent.

A 10-year-old child with cystic fibrosis presents with cough and shortness of breath. Her sputum Gram stain is seen in the image: (IMAGE) Based on the Gram stain what would be the best medium and incubation condition to optimize recovery of the organism seen? a MacConkey agar incubated in C02 b Tinsdale agar incubated in ambient air c chocolate agar incubated in C02 d CNA agar incubated in ambient air

c chocolate agar incubated in C02 c The Gram stain demonstrates numerous neutrophils and small, pleomorphic gram- negative bacilli suggestive of Haemophilus. H influenzae is an important cause of lower respiratory tract infections in patient with pre-existing lung disease such as cystic fibrosis. Haemophilus are fastidious, and require the use of an enriched medium such as chocolate agar and incubation at 35°-37°C in a moist environment supplemented with 5%-10% C02.

Cerebrospinal fluid from a febrile 25-year old man with possible meningitis is rushed to the laboratory for a stat Gram stain and culture. While performing the Gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should use a: a blood agar plate b chopped meat glucose c chocolate agar plate d Thayer-Martin plate

c chocolate agar plate C Enriched media such as chocolate agar has no inhibitory effects on bacterial growth and contains additional nutrients that supports the growth of fastidious organisms such as H influenzae and Neisseria.

A medium that aids in the presumptive identification of organisms based on their appearance on the medium is called: a enriched b selective c differential d specialized

c differential c Differential media contain compounds, often carbohydrates, that provide a presumptive identification based on colony color or a precipitate around the colony. Examples include MacConkey, Hektoen and xylose lysine desoxycholate agar.

Which compound, detected by Lugol iodine, is used in the nonimmunologic detection of Chlamydia trachomatis in cell culture? a DNA b RNA c glycogen d DNA polymerase

c glycogen c Iodine staining can be used to detect only the glycogen-rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

The organism most commonly associated with neonatal purulent meningitis is: a Neisseria meningitidis b Streptococcus pneumoniae c group B streptococci d Haemophilus influenzae

c group B streptococci c All of the organisms listed are potential causes of meningitis. Group B Streptococcus is associated with neonatal meningitis and meningitis in the elderly.

A gamma-hemolytic Streptococcus that blackens bile esculin agar but does not grow in 6.5% NaCl broth is most likely: a group B Streptococcus b Enterococcus c group D Streptococcus d Streptococcus pneumoniae

c group D Streptococcus c Group D streptococci and Enterococcus produce a positive bile esculin test; however, of these 2, only Enterococcus grows in the presence of 6.5% NaCl.

Which one of the following results is typical of Campylobacter fetus subspecies fetus? a optimal growth at 42°C b oxidase negative c growth at 37°C d catalase negative

c growth at 37°C c Most Campylobacter grow at 42°C, except C fetus. C fetus grows best at 37°C and is catalase and oxidase positive.

a catheterized urine is inoculated onto blood and MacConkey agar using a 0 01 mL loop After 48 hours. 68 colonies of a small translucent nonhemolytic organism grew on blood agar but not MacConkey. Testing reveals small gram-positive, catalase-negative cocci. The preliminary report and follow-up testing would be: a growth of 680 colonies colonies/mL of gram-positive cocci, optochin and bacitracin susceptibility tests b growth of 6,800 colonies mL of a Staphylococcus species, coagulase test to follow c growth of 6,800 colomes/mL of a Streptococcus species, esculin hydrolysis and NaCl growth test to follow d growth of 6,800 colonies/mL of a Streptococcus species, no further testing

c growth of 6,800 colomes/mL of a Streptococcus species, esculin hydrolysis and NaCl growth test to follow c The number of colonies isolated is multiplied by 100 when a 0.01 mL loop is used for inoculation. Gram-positive, catalase negative cocci are indicative of streptococci.

Which of the following would best differentiate Streptococcus agalactiae from Streptococcus pyogenes ? a ability to grow in sodium azide broth b a positive bile-esculin reaction c hydrolysis of sodium hippurate d beta-hemolysis on sheep blood agar

c hydrolysis of sodium hippurate c Of the biochemicals listed only hydrolysis of sodium hippurate will differentiate Streptococcus agalactiae {[positive) from S pyogenes (negative).

SPS is used as an anticoagulant for blood cultures because it: a inactivates penicillin and cephalosporins b prevents clumping of red cells c inactivates neutrophils and components of serum complement d facilitates growth of anaerobes

c inactivates neutrophils and components of serum complement c Most commercially available blood culture media contain sodium polyanetholsulfonate (SPS) in concentrations between 0.025 and 0.05%. SPS has anticoagulant activity, and inactivates neutrophils as well as some antibiotics including gentamicin and polymyxin. It also precipitates components of serum complement.

Quality control results for disk diffusion susceptibility tests yield the following results: aminoglycoside zones too small and penicillin zones too large. This is most likely due to the: a inoculum being too heavy b inoculum being too light c pH of Mueller-Hinton agar being too low d calcium and magnesium concentration in the agar being too high

c pH of Mueller-Hinton agar being too low c Mueller-Hinton agar used for disk diffusion susceptibility testing is standardized at pH 7.2-7.4. Penicillins function better in an acidic environment, so zone sizes would become larger if the media pH is too low. Aminoglycosides, on the other hand, are less effective in an acidic environment, so zone sizes would become smaller if the pH of the media is too low. Plates should not be incubated in a carbon dioxide atmosphere, which lowers the pH of the media.

Refer to the following image: (IMAGE) The egg depicted above is most likely to be found in children suffering from: a diarrhea b constipation c perianal itching d stomach pain

c perianal itching c The most common sign of Enterobius vermicularis infection is intense perianal itching.

Which of the following groups of specimens would be acceptable for anaerobic culture? a vaginal, eye b ear, leg tissue c pleural fluid, brain abscess d urine, sputum

c pleural fluid, brain abscess c Materials collected from sites not harboring indigenous flora (sterile body fluids, abscess exudate and tissue) should be cultured for anaerobic bacteria. However, since anaerobes normally inhabit the skin and mucus membranes as part of the indigenous flora, specimens such as urine, sputum, and vaginal, eye and ear swabs are not acceptable for culture.

In the optochin (ethylhydrocupreine hydrochloride) susceptibility test, if there is a zone of inhibition of 19-30 mm surrounding the disk following overnight incubation at 37"C, the colony most likely consists of: a staphylococci b streptococci c pneumococci d intestinal bacilli

c pneumococci c Optochin susceptibility is used to differentiate S pneumoniae, which are susceptible, from other alpha-hemolytic streptococci, which are resistant.

In preparing an India ink slide, the technician should ensure that the. a CSF is unspun b sputum is well mixed c proper amount of reagent is added d slide is properly dried first

c proper amount of reagent is added Interpretation of India ink preparations can be hindered if too much India ink is added, blocking the transmission of light. Equal parts of India ink and CSF should be combined.

Characteristics of the HACEK group of bacteria include: a association with urinary tract infections b Gram stain of pleomorphic gram-positive bacilli c requirement of 5%-10% C02 for growth d requirement of 42°C for growth

c requirement of 5%-10% C02 for growth c The HACEK group of organisms ONLY are gram-negative bacilli that require increased C02 for growth. They are commonly associated with endocarditis, and include Haemophilus species (especially H aphrophilus), Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella species.

A technologist is reading a Gram stain from a CSF and observes many neutrophils and lancet-shaped gram-positive diplococci. Which set of chemistry and hematology CSF results would most likely be seen in someone with this type of infection? CSF results WBC Glucose Protein A increased increased increased B decreased decreased decreased C increased decreased increased D decreased increased decreased a result A b result B c result C d result D

c result C c The classic CSF alterations associated with bacterial meningitis are a high WBC count with a neutrophil predominance as well as a low CSF glucose and a high CSF 72 protein.

Polyvinyl alcohol used in the preparation of permanently stained smears of fecal material: a concentrates eggs b dissolves artifacts c serves as an adhesive d enhances stain penetration

c serves as an adhesive c Polyvinyl alcohol is an adhesive and is used in the preparation of smears for stains, such as trichrome.

A Gram stain of a necrotic wound specimen showed large gram-positive bacilli. There was 3+ growth on anaerobic media, with colonies producing a double zone of hemolysis. To identify the organism, the microbiologist should: a determine if the organism ferments glucose b perform the oxidase test c set up egg yolk agar plate d test for bile tolerance

c set up egg yolk agar plate c The Gram stain and double zone of hemolysis are characteristics of Clostridium perfringens. C perfringens is lecithinase positive on the egg yolk agar test for lecithinase and lipase.

Tests for beta-lactamase production in Haemophilus influenzae: a are not commercially available b include tests that measure a change to an alkaline pH c should be performed on all blood and CSF isolates d are not valid for any other bacterial species

c should be performed on all blood and CSF isolates c As many as 20%-40% of H influenzae produce beta-lactamases. Detection of these enzymes should be performed on any isolate considered to be a pathogen using the chromogenic cephalosporin (nitrocefm) test.

A fungal isolate from the sputum of a patient with a pulmonary infection is suspected to be Histoplasma capsulatum. Tuberculate macroconidia were seen on the hyphae of the mo ld phase which was isolated at room temperature on Sabouraud dextrose agar containing chloramp enic and cycloheximide (SDA-CC). A parallel set of cultures incubated at 35°C showed bacterial growt on SDA, but no growth on SDA-CC. Which of the following is the appropriate course of action. a repeat subculture of the mold phase to tubes of moist SDA-CC, incubate at 35°C b subculture the mold phase to tubes of moist BHI-blood media, incubate at 25°C c subculture the mold phase to moist BHI-blood media, incubate at 35°C d perform animal inoculation studies

c subculture the mold phase to moist BHI-blood media, incubate at 35°C c Conversion of thermally dimorphic fungi in culture requires the use of moist enriched (blood-containing) agar incubated at 35°C.

Salmonella enteritidis is isolated from multiple blood cultures in a patient with fever. Susceptibility results are as follows: ampicillin-susceptible ceftriaxone-susceptible ciprofloxacin-susceptible trimethoprim/sulfamethoxazole-resistant. What is the next best step? a report all of the susceptibility testing results with no changes b perform a beta-lactamase test on the isolate before reporting the ampicillin as susceptible c test the isolate against nalidixic acid and if resistant report the ciprofloxacin as resistant d report gentamicin since the trimethoprim/sulfamethoxazole is resistant

c test the isolate against nalidixic acid and if resistant report the ciprofloxacin as resistant c Extraintestinal isolates of Salmonella should be tested for resistance to nalidixic acid in addition to fluoroquinolones. Fluoroquinolones susceptible stains of Salmonella that are resistant to nalidixic acid may be associated with clinical failure or delayed response to therapy. In the case where ciprofloxacin is susceptible and nalidixic acid is resistant the nalidixic acid result should be used for reporting.

Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antibiotics tested. The testing was repeated using media from a previously used lot number, and all zone sizes were acceptable. Which of the following best explains the unacceptable zone sizes? a the antibiotic disks were not stored with the proper desiccant b the depth of the media was too thick c the depth of the media was too thin d the antibiotic disks were not properly applied to the media

c the depth of the media was too thin c All Mueller-Hinton agar used for disk diffusion susceptibility testing should be poured to a depth of 4mm. If the depth of the media is <4mm, this may be associated with excessively large zones and false- positive susceptibility results. Agar that is >4mm in depth may cause excessively small zone sizes.

During the past month, Staphylococcus epidermidis has been isolated from bloo0d cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that: a the blood culture media are contaminated with this organism b the hospital ventilation system is contaminated with Staphylococcus epidermidis c there has been a break in proper skin preparation before drawing blood for culture d a relatively virulent isolate is being spread from patient to patient

c there has been a break in proper skin preparation before drawing blood for culture c Appropriate skin antisepsis is the most important factor in preventing contaminated blood cultures. Staphylococcus epidermidis is a common blood culture contaminant because it is a common inhabitant of the skin.

Anaerobic infections differ from aerobic infections in which of the following? a they usually respond favorably with aminoglycoside therapy b they usually arise from exogenous sources c they are usually polymicrobic d Gram stains of specimens are less helpful in diagnosis

c they are usually polymicrobic c Most infections involving anaerobes are polymicrobic and can include obligate aerobes, facultative anaerobes, microaerophilic bacteria in addition to anaerobic bacteria.

The ability to detect oxacillin-resistant Staphylococcus aureus may be enhanced by: a shortening incubation of standard susceptibility plates b incubating susceptibility plates at 39°-41°C c using Mueller-Hinton broth with 2% NaCl d adjusting inoculum to 0.1 McFarland before inoculating susceptibility plates

c using Mueller-Hinton broth with 2% NaCl c For optimum detection of oxacillin- resistant S aureus, a suspension with a turbidity equivalent to a 0.5 McFarland standard should be inoculated into a cation- adjusted Mueller-Hinton broth with 2% NaCl. Plates should be incubated at 35 ± 2°C for 24 hours. Temperatures above 35°C may not detect oxacillin resistance.

In a disk diffusion susceptibility test, which of the following can result if disks are placed on the inoculated media and left at room temperature for an hour before incubation? a the antibiotic would not diffuse into the medium, resulting in no zone b zones of smaller diameter would result c zones of larger diameter would result d there would be no effect on the final zone diameter

c zones of larger diameter would result c A delay of more than 15 minutes between placing the disks on an inoculated plate and incubation permits excess prediffusion of the antimicrobial agent from the disk. This would result in a larger than expected zone diameter.

On day 3 of a fungal culture, grayish cottony growth is observed that is filling the container. The most likely mold isolated is a: a dermatophyte b dimorphic mold c zygomycete d dematiaceous mold

c zygomycete c Zygomycetes grow rapidly and fill the dish with cotton candy-like growth.

The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is: a 4°C b 20°C c 25°C d 42°C

d 42°C d Campylobacter jejuni/coli grow better at 42°C than 37°C and other organisms in the colon are inhibited at this high temperature.

A sheep blood agar plate inoculated with 0.001mL of urine grows 70 colonies of Staphylococcus aureus. How many colony forming units per mL of urine be reported? a 70 b 700 c 7,000 d 70,000

d 70,000 d When 0.001 mL of urine is plated, the growth of one colony is equivalent to 1000 CFU/mL. Thus 70 colonies is 70,000 CFU/mL.

A patient with a nosocomial pneumonia has a sputum Gram stain that shows many neutrophils MLS and numerous small gram-negative coccobacilli. The organism grew in 24 hours as a mucoid, hemolytic colony on blood agar and a colorless colony on a MacConkey agar. The organism had the following characteristics: oxidase: negative catalase: positive nitrate: negative ONPG: negative ornithine decarboxylase: negative lysine decarboxylase: negative The organism is: a Stenotrophomonas maltophilia b Alcaligenes faecalis c Moraxella lacunata d Acinetobacter baumannii

d Acinetobacter baumannii d Alcaligenes and Moraxella are oxidase positive; Stenotrophomonas is a gram-negative bacillus and is lysine and ONPG positive; Acinetobacter baumais nitrate and ONPG negative, and it is a gram- negative coccobacillus.

Which of the following genera include anaerobic gram-negative nonsporulating bacilli? a Brucella b Pasteurella c Actinomyces d Bacteroides

d Bacteroides d Brucella and Pasteurella are aerobic, gram-negative bacilli, and Actinomyces is on anaerobic gram-positive bacillus. Bacteroides species are anaerobic, gram-negative bacilli.

A culture from an infected dog bite on a small boys finger yielded a small, gram-negative cobacillus that was smooth, raised and beta-hemolytic on blood agar. The isolate grew on MacConkev agar, forming colorless colonies. The organism was motile, cataiase positive, oxidase e reduced nitrate, and was urease positive within 4 hours. No carbohydrates were :• : minted The most likely identification of this isolate is: a Brucella canis b Yersinia pestis c Francisella tularensis d Bordetella bronchiseptica

d Bordetella bronchiseptica d bordetella bronchiseptica are normal flora the respiratory tract of various animals. reaction is that it is rapidly urea Positive (within 4 hours). Brucella is also urea positive, but does not grow on MacConkey

An aerobic, gram-negative coccobacillus was isolated on Bordet-Gengou agar from a nasopharyngeal swab 48 hours after culture from a 6-month-old infant with suspected pertussis. The organism exhibited the following characteristics: MacConkey agar: no growth urea: negative at 4 hours, positive at 24 hours oxidase: negative cataiase: positive The most probable identification of this isolate is: a Moraxella la cun at a b Pasteurella ureae c Bordetella pertussis d Bordetella parapertussis

d Bordetella parapertussis d The oxidase and urea reactions differentiate Bordetella pertussis and B parapertussis. B pertussis is oxidase positive and urea negative.

An isolate of an unknown beta-hemolytic Streptococcus is streaked perpendicular to a streak of beta-lysin-producing Staphylococcus aureus. After incubation a zone of arrowhead hemolysis is noted at the interface of the 2 streaks. What is the name of the test and the presumptive identification of the unknown Streptococcus? a hippurate hydrolysis and 5 agalactiae b CAMP test and S pyogenes c hippurate hydrolysis and S pyogenes d CAMP test and S agalactiae

d CAMP test and S agalactiae d The question describes the CAMP test, which is positive for Streptococcus agalactiae.

The formation of germ tubes presumptively identifies. a Candida tropicalis b Candida parapsilosis c Candida glabrata d Candida albicans

d Candida albicans d Candida albicans produces germ tubes.

A Gram stain from a swab of a hand wound reveals: moderate neutrophils no squamous epithelial cells moderate gram-positive cocci in chains moderate large gram-negative bacilli Select the appropriate media that will selectively isolate each organism. a KV-laked agar, Thayer-Martin b sheep blood, MacConkey c Columbia CNA, chocolate d Columbia CNA, MacConkey

d Columbia CNA, MacConkey d Columbia CNA agar is a selective medium used for the isolation of gram- positive organisms. The medium contains colistin and nalidixic acid, which inhibits gram-negative organisms. MacConkey agar is a selective and differential medium used for the isolation of gram-negative organisms. The medium contains bile and crystal violet, which inhibits gram-positive organisms.

Which of the following may be used as a positive quality control organism for the bile esculin test? a Staphylococcus epidermidis b Staphylococcus aureus c Streptococcus pyogenes d Enterococcus faecalis

d Enterococcus faecalis d Enterococcus is positive for the bile esculin test while Streptococcus pyogenes and staphylococci are negative.

Quality control of the spot indole test requires the use of ATCC cultures of: a Pseudomonas aeruginosa/Proteus mirabilis b Salmonella typhi/Shigella sonnei c Escherichia coli/Proteus vulgaris d Escherichia coli/Enterobacter cloacae

d Escherichia coli/Enterobacter cloacae d Quality control of indole requires both a positive and a negative control. E coli and E cloacae respectively produce a positive and negative reaction with indole.

Which feature distinguishes Erysipelothrix rhusiopathiae from other clinically significant non-spore-forming, gram-positive, facultatively anaerobic bacilli? a "tumbling" motility b beta-hemolysis c more pronounced motility at 25°C than 37°C d H2S production

d H2S production d Erysipelothrix rhusipathiae is the only gram-positive bacillus that produces hydrogen sulfide when inoculated into triple sugar iron agar.

A jaundiced 7-year-old boy, with a history of playing in a pond in a rat infested area, has a urine specimen submitted for a direct darkfield examination. Several spiral organisms are seen. Which of the following organisms would most likely be responsible for the patient s condition? a Spirillum minus b Streptobacillus moniliformis c Listeria monocytogenes d Leptospira interrogans

d Leptospira interrogans d Leptospira are spiral-shaped organisms with hooked ends. They are ubiquitous in water (eg, lakes, ponds) and associated with renal infection in animals. Leptospirosis is a zoonosis, and humans are usually infected via direct or indirect contact with the urine of infected animals (including rats). Between 5%-10% of patients with leptospirosis have the icteric form and develop jaundice, and may develop acute renal failure.

Chocolate agar base containing vancomycin, colistin, anisomycin, and trimethoprim is also known a EMB agar b modified Thayer-Martin agar c Columbia CNA agar d Martin Lewis agar

d Martin Lewis agar d Martin Lewis agar is a modification of the modified Thayer Martin formulation, and contains a higher concentration of vancomycin and anisomycin instead of nystatin. These modifications provide better inhibition of gram-positive organisms and Candida.

A cell culture line used for the recovery of Chlamydia trachomatis from clinical specimens is: a HeLa 229 b Hep-2 c BHK-21 d McCoy

d McCoy d McCoy cells, in addition to buffalo green monkey kidney cells, are susceptible to infection with Chlamydia trachomatis, and are used routinely for the recovery of C trachomatis in culture.

Which of the following organisms may be mistaken for Neisseria gonorrhoeae in Gram stained smears of uterine cervix exudates? a Lactobacillus species b Streptococcus agalactiae c Pseudomonas aeruginosa d Moraxella osloensis

d Moraxella osloensis d Moraxella osloensis is a gram-negative coccobacillus that is often plump and occurs in pairs and demonstrates a morphology similar to Neisseria. The presence of this organism in endocervical specimens contaminated with vaginal secretions can lead to over interpretation of smears for N gonorrhoeae.

Primary amoebic encephalitis may be caused by: a Entamoeba coli b Dientamoeba fragilis c Endolimax nana d Naegleria fowleri

d Naegleria fowleri d Naegleria fowleri is the etiologic agent of primary amoebic encephalitis.

A fungus superficially resembles Penicillium species but may be differentiated because its phialides are Ion8 and tapering and bend away from the central axis. The most probable identification is: Exophiala b Acremonium c Cladosporium d Paecilomyces

d Paecilomyces d Elongated and tapered phialides (tenpins) are characteristic of Paecilomyces.

Organisms that can be easily identified to the species level from the ova in fecal specimens include: a Metagonimus yokogawai, Heterophyes heterophyes b Taenia solium, Taenia saginata c Necator americanus, Ancylostoma duodenale d Paragonimus westermani, Hymenolepis nana

d Paragonimus westermani, Hymenolepis nana d Of the organisms listed, only Paragonimus and Hymenolepis can be identified to the species level by the appearance of their ova in stool.

The stock cultures needed for quality control testing of deamination activity are: a Escherichia coli/Klebsiella pneumoniae b Salmonella typhimurium/Escherichia coli c Escherichia coli/Pseudomonas aeruginosa d Proteus mirabilis/Escherichia coli

d Proteus mirabilis/Escherichia coli d Of the organisms listed only Proteus mirabilis is phenylalanine deaminase positive

A nonfermenting gram-negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on sheep blood agar has a grape-like odor. The organism is: a Burkholderia cepacia b Moraxella lacunata c Chryseobacterium (Flavobacterium) meningosepticum d Pseudomonas aeruginosa

d Pseudomonas aeruginosa d Pseudomonas aeruginosa often has a sweet odor that smells like grapes.

An organism isolated from the surface of a skin burn is found to produce a diffusible green pigment on a blood agar plate. Further studies of the organism would most likely show the organism to be: a Staphylococcus aureus b Serratia marcescens c Flavobacterium meningosepticum d Pseudomonas aeruginosa

d Pseudomonas aeruginosa d Pseudomonas aeruginosa produces the blue-green pigment, pyocyanin.

Which of the following tests is used to monitor bactericidal activity during antimicrobic therapy in cases of endocarditis? a Elek b tolerance c Sherris synergism d Schlichter

d Schlichter d The serum bactericidal, or Schlichter, test can be used to assess the activity of patient's serum when they are receiving long-term therapy for endocarditis or osteomyelitis. High titers of antibacterial activity in the serum suggest adequate dosing, a nontolerant isolate or normal elimination of the antibiotic.

The stock cultures needed for quality control testing of deoxyribonuclease (DNase) production are: a Salmonella typhimurium /Escherichia coli b Escherichia coli/Pseudomonas aeruginosa c Proteus mirabilis /Escherichia coli d Serratia marcescens/Escherichia coli

d Serratia marcescens/Escherichia coli d Of the organisms listed only Serratia marcescens is DNase positive.

Which one of the following genera is among the least biochemically reactive members of the Enterobacteriaceae? a Proteus b Pseudomonas c Citrobacter d Shigella

d Shigella d Shigella is lactose negative, most species do not produce gas, are VP, urea, lysine decarboxylase and citrate negative, and they are nonmotile.

A TSI tube inoculated with an organism gave the following reactions: alkaline slant, acid butt, no H2S, no gas produced This organism is most likely: a Yersinia enterocolitica b Salmonella typhi c Salmonella enteritidis d Shigella dysenteriae

d Shigella dysenteriae d Salmonella produce H2S in TSI and Yersinia produces an acid slant and acid butt. Shigella fits this biochemical profile.

Of the following bacteria, the most frequent cause of prosthetic heart valve infections occurring within 2-3 months after surgery is: a Streptococcus pneumoniae b Streptococcus pyogenes c Staphylococcus aureus d Staphylococcus epidermidis

d Staphylococcus epidermidis d Staphylococcus epidermidis is the most common cause of prosthetic valve endocarditis.

Diagnosis of typhoid fever can be confirmed best by culture of : a stool b urine c blood d bone marrow

d bone marrow d The sensitivity of blood culture is only 50%-70%. Stool cultures are positive in <50% of patients and urine cultures are positive even less frequently. Bone marrow has a sensitivity of up to 90%. Higher colony counts are present in bone marrow and counts are not decreased by up to 5 days of antimicrobial therapy prior to specimen collection.

A gram-positive coccus isolated from a blood culture has the following characteristics: optochin susceptibility: negative bacitracin (0.04 U) susceptibility: negative bile esculin hydrolysis: negative hippurate hydrolysis: positive catalase: negative This organism is most likely: a Staphylococcus aureus b Streptococcus pneumoniae c Streptococcus pyogenes d Streptococcus agalactiae

d Streptococcus agalactiae d Streptococcus agalactiae is catalase and bile esculin hydrolysis negative and bacitracin and optochin resistant. Streptococcus agalactiae hydrolyzes hippurate.

An important cause of acute exudative pharyngitis is: a Staphylococcus aureus (beta-hemolytic) b Streptococcus pneumoniae c Streptococcus agalactiae d Streptococcus pyogenes

d Streptococcus pyogenes d Streptococcus pyogenes is the cause of exudative pharyngitis, commonly called strep throat.

The term "internal autoinfection" is generally used in referring to infections with. a Ascaris lumbricoides b Necator americanus c Trichuris trichiura d Strongyloides stercoralis

d Strongyloides stercoralis d Strongyloides stercoralis rhabditiform larvae are capable of transforming into filariform (infective) larvae in the intestines of immunocompromised patients. This establishes an autoinfective cycle.

A college student attended a beach party where raw oysters and other shellfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram-negative bacilli with the following characteristics: oxidase: positive MacConkey agar: pink colonies 0/129 (150 pg): susceptible Thu most likely organism is: a Aeromonas hydrophila b Pseudomonas putida c Serratia marcescens d Vibrio vulnificus

d Vibrio vulnificus d The consumption of raw shell fish is only a risk factor for Vibrio vulnificus and the biochemical reactions support a Vibrio species. V vulnificus is one of the only vibrios that ferments lactose.

Refer to the following illustration... Examine the broth microdilution suceptibility test shown above and determine the MIC for gentamicin. a >64ug/mL b 32 ug/mL c 16 pg/mL d <2 pg/mL

d When reading a broth microdilution susceptibility test, growth in each well is determined by comparison with the growth control well and indicated by turbidity. The well with the lowest concentration of antibiotic displaying no growth is read as the minimum inhibitory concentration (MIC).

Which of the following is the most appropriate organism and media combination? a Legionella species—Regan Lowe b Clostridium difficile—phenylethyl alcohol (PEA) c Campylobacter species—charcoal yeast extract d Yersinia enterocolitica—cefsulodin-irgasan-novobiocin (CIN)

d Yersinia enterocolitica—cefsulodin-irgasan-novobiocin (CIN) d CIN agar is a selective and differential medium for the isolation and differentiation of Y enterocolitica. This medium contains sodium desoxycholate, crystal violet, cefsulodin, irgason (triclosan), and novobiocin as selective agents, and mannitol as the carbohydrate.

Gram stain of a thigh wound showed many gram-positive spore-forming bacilli. The specimen was placed on brain heart infusion blood agar and incubated aerobically at 35°C for 3 days. At the end of that time, the plates showed no growth. The most likely explanation is that some of the specimen should have been incubated: a on chocolate agar b for 5 days c under 5% CO2 d anaerobically

d anaerobically d The specimen Gram stain suggests the presence of Bacillus or Clostridium. Since no growth was observed aerobically, the specimen should be inoculated to media that are incubated anaerobically.

Penicillium can best be separated from Aspergillus by: a color of the colonies b optimum growth temperature c presence of rhizoids d arrangement of the conidia on the conidiophore

d arrangement of the conidia on the conidiophore d Microscopic morphology (arrangement only of the conidia on the conidiophore) is used to differentiate Penicillium from Aspergillus.

Which of the following is the most appropriate method for collecting a urine specimen from a patient with an indwelling catheter? a remove the catheter, cut the tip, and submit it for culture b disconnect the catheter from the bag, and collect urine from the terminal end of the catheter c collect urine directly from the bag d aspirate urine aseptically from the catheter tubing

d aspirate urine aseptically from the catheter tubing d Indwelling catheters are closed systems, and should not be disconnected for specimen collection. Urine samples should not be collected from catheter bags, and Foley catheter tips are unsuitable for culture because they are contaminated with colonizing organisms. Urine from indwelling catheters should be collected by aseptically puncturing the tubing (collection port).

Haemophilus influenzae becomes resistant to ampicillin when the organism produces a(n): a capsule of polysaccharide material b affinity for the beta-lactam ring of the ampicillin c porphobilinogen d beta-lactamase enzyme

d beta-lactamase enzyme d The beta-lactamase enzyme produced by Haemophilus influenzae inactivates the antibiotics that have a beta-lactam ring in their structure, such as penicillins and cephalosporins.

Streptococcus pneumoniae can be differentiated best from the viridans group of streptococci by a Gram stain b the type of hemolysis c colonial morphology d bile solubility

d bile solubility d Bile solubility testing of alpha-hemolyt streptococci differentiates S pneumoniae (soluble) from other alpha-hemolytic streptococci such as viridans streptococci (insoluble).

Viridans streptococci can be differentiated from Streptococcus pneumoniae by: a alpha hemolysis b morphology c catalase reaction d bile solubility

d bile solubility d Bile solubility testing of alpha-hemolytic streptococci differentiates S pneumoniae (soluble) from other alpha-hemolytic streptococci, such as viridans streptococci (insoluble).

The method of choice to detect Acanthamoeha sp from corneal ulcer scrapings is: a Novy, MacNeal and Nicolle (NNN) medium b culture on McCoy cells c direct exam d blood agar flooded with a 24-hour growth of E coli

d blood agar flooded with a 24-hour growth of E coli d The recommended technique for culturing Acanthamoeba is the use of nonnutrient agar seeded with a lawn of E coli. Specimens with suspected Acanthamoeba are inoculated onto a freshly inoculated lawm of E coli, incubated and observed for 7 days. Identification is based on the characteristic patterns of locomotion and morphologic features of the trophic and cystic forms.

Propionibacterium acnes is most often associated with: a normal oral flora b post-antibiotic diarrhea c tooth decay d blood culture contamination

d blood culture contamination d Propionibacterium acnes is part of the normal flora of the skin, so it is frequently isolated from improperly collected blood cultures.

A sputum specimen is received for culture and Gram stain. The Gram stained smear from this specimen is seen in the image (total magnification 100x): (image) The technologist's best course of action would be to: a inoculate appropriate media and incubate anaerobically b inoculate appropriate media and incubate aerobically c call the physician and notify him of this "life-threatening" situation d call the patient care area and request a new specimen

d call the patient care area and request a new specimen d There are several sputum-screening systems for assessing the quality of respiratory specimens. In general, neutrophils are a positive indicator of quality, and squamous epithelial cells are a negative indicator of quality, suggesting oropharyngeal contamination. This specimen contains an abundance of squamous cells (> 10/low power field), and would be unacceptable for culture.

The most common cause for failure of a GasPak™ anaerobic jar to establish an adequate environment for anaerobic incubation is: a the failure of the oxidation-reduction potential indicator system due to deterioration of methylene blue b the failure of the packet to generate adequate H2 and/or C02 c condensation of water on the inner surface of the jar d catalysts that have become inactivated after repeated use

d catalysts that have become inactivated after repeated use d The 2 most common causes of failure of the GasPak™ system is a defective gasket in the jar lid that allows escape of gas from inside the jar and inactivated catalyst pellets.

Proper media for culture of a urethral discharge from a man include: a sheep blood and phenylethyl alcohol agars b eosin-methylene blue and sheep blood agars c thioglycollate broth and chocolate agar d chocolate and modified Thayer-Martin agars

d chocolate and modified Thayer-Martin agars d Chocolate agar and chocolate agar- based selective media should be used for recovery of Neisseria gonorrhoeae from urethral discharge. Chocolate agar provides the nutrients required by N gonorrhoeae and selective media contains antimicrobial agents that inhibits other organisms and permits recovery of pathogenic Neisseria.

Two blood cultures are positive for yeast from a patient with an intravenous catheter. One T culture grew Candida albicans, while the other grew Candida krusei. Which medium should the technologist use to subculture the blood bottles to in order to verify that the cultures are pure? a Sabouraud dextrose agar b potato dextrose agar c cornmeal agar d chromogenic agar

d chromogenic agar d Chromogenic agar is extremely effective only in detecting mixed yeast populations in clinical specimens.

A laboratory aid receives a bronchoscopy sample with the request for culture of Legionella. The assistant asks a microbiologist for direction on plating protocol. The correct response from t e microbiologist is: a culture on thiosulfate citrate bile salt media b incubate the culture media anaerobically c reject the specimen and request a sputum sample d culture on buffered charcoal yeast extract agar with antibiotics

d culture on buffered charcoal yeast extract agar with antibiotics d Buffered charcoal yeast extract agar is recommended for culture of specimens for Legionella.

Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchoalveolar lavage (BAL) specimen from this patient had a positive antigen test for Legionella but no organisms were recovered on buffered charcoal yeast extract medium after 2 days of incubation. The best explanation is that the: a antibody titer represents an earlier infection b positive antigen test is a false positive c specimen was cultured on the wrong media d culture was not incubated long enough

d culture was not incubated long enough d Media for isolation of Legionella should be incubated at 35°-37°C for at least 7 days.

A first morning sputum is received for culture of mycobacteria. It is digested and concentrated by the N-acetyl-L-cysteine alkali method. Two Lowenstein-Jensen slants are incubated in the dark at 35°C with 5%-10% C02. The smears reveal acid-fast bacilli, and after 7 days no growth appears on the slants. The best explanation is: a improper specimen submitted b incorrect concentration procedure c exposure to C02 prevents growth d cultures held for insufficient length of time

d cultures held for insufficient length of time d Many species of mycobacteria are slow growing, and may take up to 12 weeks for growth.

Which of the following methods is inadequate for the detection of vancomycin-intermediate S aureus? a broth macrodilution b agar dilution c gradient diffusion d disk diffusion

d disk diffusion The disk diffusion procedure will not differentiate S aureus strains with reduced susceptibility to vancomycin (MICs 4-8 pg/mL) from susceptible stains even when incubated for 24 hours.

What material should be used to prepare slides for direct smear examination for virus detect: special stains or FA technique? a vesicular fluid b leukocytes from the edge of the lesion c the top portion of the vesicle d epithelial cells from the base of the lesion

d epithelial cells from the base of the lesion d Since viruses are intracellular organisms, the collection of cellular material is required to be able to demonstrate virus using stains or fluorescent techniques. Scrapings of the base of a vesicle are required to collect cellular material.

The appropriate specimen for the diagnosis of mucormycosis is: a nasal swab b sputum c sinus washing d eschar biopsy

d eschar biopsy d Mucormycosis is an aggressive infection where biopsy, curettage or fine-needle aspiration is essential for diagnosis.

Listeria can be confused with some streptococci because of its hemolysis and because it is: a nonmotile b catalase negative c oxidase positive d esculin positive

d esculin positive d Listeria may be confused with some streptococci because Listeria is beta- hemolytic and is capable of hydrolyzing esculin.

An aspirate of a deep wound was plated on blood agar plates and incubated aerobically and anaerobically. At 24 hours there was growth on both plates. This indicates that the organism is a(n): a nonfermenter b obligate anaerobe c aerobe d facultative anaerobe

d facultative anaerobe d Facultative anaerobes are organisms that can grow under both aerobic and anaerobic conditions.

Middlebrook 7H10 and 7H11 media must be refrigerated in the dark, and incubated in the dark as well. If these conditions are not met, the media may prove toxic for mycobacteria because: a carbon dioxide will be released b growth factors will be broken down c light destroys the ammonium sulfate d formaldehyde may be produced

d formaldehyde may be produced d If exposed to light, agar-based media such as 7H11 may release formaldehyde, which is toxic to mycobacteria.

Enzymatic drug modification is a mechanism of resistance for which antimicrobial? a levofloxacin b sulfamethoxazole c vancomycin d gentamicin

d gentamicin d Aminoglycoside modifying enzymes modify aminoglycosides, such as gentamicin, resulting in poor binding to the bacterial ribosome. Resistance to levofloxacin, vancomycin and sulfamethoxazole is a result of nonenzymatic alteration of the antimicrobial target causing reduced antibiotic binding or activity.

The Image depicts a Gram stain (final magnification l,000x) of a knee fluid from a patient who has recently undergone knee replacement surgery: The best interpretation of this Gram stain is: a gram-positive cocci suggestive of Staphylococcus b gram-positive bacilli suggestive of Corynebacterium c gram-positive bacilli suggestive of Listeria d gram-positive cocci suggestive of Streptococcus

d gram-positive cocci suggestive of Streptococcus d The Gram stain depicts gram-positive cocci arranged in chains. Members of the genus Streptococcus characteristically grow in pairs and chains, and tend to chain more in fluid. Staphylococci are also gram-positive cocci that can appear singly, in pairs, short chains or, more typically, clusters.

If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is: a a positive test for cytochrome oxidase b oxidative metabolism in the OF test c production of fluorescein pigment d growth at 42*C

d growth at 42*C d Pseudomonas aeruginosa grows at 42°C, but this temperature is inhibitory for other Pseudomonas species.

Nutritionally deficient streptococci are: a enterococci b group D nonenterococci c cell wall-deficient streptococci d in the genera Granulicatella and Abiotrophia

d in the genera Granulicatella and Abiotrophia d Organisms that used to be categorized as nutritionally variant or deficient streptococci have been reclassified into the genera Abiotrophia and Granulicatella.

To quality control the autoclave, a vial of Bacillus stearothermophilus is autoclaved and should then be: a inoculated to blood agar b incubated at 37*C c inoculated to chocolate agar d incubated at 56*C

d incubated at 56*C d Bacillus stearothermophilus is commonly used as an indicator organism for the appropriate functioning of autoclaves. Unlike most Bacillus species, B stearothermophilus grows at 56°C.

Which one of the following combinations of organisms would be appropriate as controls to test the functions listed? a beta-hemolysis-negative Escherichia coli and Streptococcus pyogenes b catalase-negative Staphylococcus aureus and Staphylococcus epidennidis c H2S production-negative Proteus mirabilis and Staphylococcus epidermidis d indole-negative Escherichia coli and Proteus mirabilis

d indole-negative Escherichia coli and Proteus mirabilis d Of the combinations listed, the use of E coli and Proteus mirabilis will produce a positive and negative result for indole respectively. The remainder of the organisms are all positive for the test described

Which of the following is a growth requirement for the isolation of Leptospira? a an atmosphere of 10% C02 b an incubation temperature of 4°C c 4-5 day incubation d medium containing 10% serum plus fatty acids

d medium containing 10% serum plus fatty acids d Leptospira cultures are incubated in the dark for up to 6 weeks in ambient air at 28°-30°C, and examined weekly by darkfield microscopy. Fletcher semisolid agar contains peptone, bee extract and rabbit serum, which create an enriched medium to support the growth of leptospires.

Antifungal susceptibility tests for yeasts are: a performed routinely b highly reproducible c not clinically relevant d more useful in identifying resistant strains

d more useful in identifying resistant strains d Many factors influence clinical response to an antifungal agent; studies have shown that strains that are resistant in vitro are less likely to show a clinical response in vivo.

On a culture suspected to be Mycobacterium tuberculosis, the most important test to perform is: a catalase production b tellurite reduction c Tween® 80 hydrolysis d niacin production

d niacin production d Growth rate, colony morphology and positive niacin differentiates Mycobacterium tuberculosis from other mycobacteria.

The most sensitive substrate for the detection of beta-lactamases is: a penicillin b ampicillin c cefoxitin d nitrocefin

d nitrocefin d The chromogenic cephalosporin test using nitrocefin is the most sensitive and specific test for detection of beta lactamase. Acidimetric tests employing penicillin are less expensive, but not as sensitive, as the nitrocefin assay.

Which of the following antimicrobials would be inappropriate to report on an E coli isolated from a wound culture? a gentamicin b ampicillin c cefazolin d nitrofurantoin

d nitrofurantoin d Certain antimicrobials, such as nitrofurantoin and norfloxacin, are used only or primarily to treat urinary tract infections. These agents should not be reported for pathogens recovered from other sites of infection.

A vaginal smear is submitted for a Gram stain for Neisseria gonorrhoeae. The technologist finds the following results on the Gram stain: many white blood cells few epithelial cells many gram-positive bacilli few gram-negative diplococci few gram-positive cocci in chains The technologist should: a report out smear positive for gonorrhea b report out smear negative for gonorrhea c request a new specimen due to number of white blood cells d not read or report a Gram stain on a vaginal specimen

d not read or report a Gram stain on a vaginal specimen d Because of the presence of nonpathogenic Neisseria in the female genital tract, Gram stain does not differentiate these organisms from Ngonorrhoeae. For this reason Gram stain results should not be reported on vaginal specimens.

An urethral swab obtained from a man with an urethral exudate was plated directly on chocolate agar and modified Thayer-Martin agar, and a Gram stain was made. The Gram stain showed gram- negative diplococci. The culture plates were incubated at 35°C, but had no growth at 48 hours. The most likely failure for organism growth is that the: a wrong media were used b Gram stain was misread c organism only grows at room temperature d organism requires CO2 for growth

d organism requires CO2 for growth d Neisseria gonorrhoeae requires an enhanced carbon dioxide atmosphere for optimal growth.

An expectorated sputum is sent to the laboratory for culture from a patient with respiratory distress. The Gram stain of the specimen shows many squamous epithelial cells (>25/lpf) and rare neutrophils. The microscopic appearance of the organisms present include: moderate gram-positive cocci in chains and diplococci moderate gram-negative diplococci moderate palisading gram-positive bacilli all in moderate amounts This Gram stain is most indicative of: a a pneumococcal pneumonia b an anaerobic infection c an Haemophilus pneumonia d oropharyngeal flora

d oropharyngeal flora d Sputum specimen quality is assessed to determine if the specimen is representative of the site of infection. The presence of white blood cells is an indicator of infection, and presence of squamous epithelial cells is an indicator of oropharyngeal contamination. In this specimen, >25 epithelial cells per low power field is an indicator of poor specimen quality, and the bacteria present are representative of oropharyngeal flora.

The method used for processing specimens for mycobacterial culture contaminated with Pseudomonas is: a N-acetyl-L-cystine and NaOH b NaOH c zephiran-trisodium phosphate d oxalic acid

d oxalic acid d The oxalic acid method is superior to alkali methods for processing specimens contaminated with Pseudomonas.

Differentiating tests that will separate Burkholderia from Stenotrophomonas include. a Gram stain reaction b growth on MacConkey agar c glucose fermentation d oxidase

d oxidase d Both organisms are gram-negative bacilli and grow on MacConkey agar. Neither ferments glucose. Stenotrophomonas is oxidase negative, while most other nonfermenters are oxidase positive.

Artifacts found in a stool specimen that can be confused with ova or cysts are: a partially digested meat fibers b degenerated cells from the gastrointestinal mucosa c dried chemical crystals d pollen grains

d pollen grains d Pollen grains are common artifacts in stool specimens submitted for ova and parasite examination. Their appearance is similar to protozoan cysts.

The most rapid method for detection of Francisella tularensis is: a serological slide agglutination utilizing specific antiserum b dye stained clinical specimens c fluorescent antibody staining techniques on clinical specimens d polymerase chain reaction

d polymerase chain reaction d Methods for rapid diagnosis of Francisella tularensis include fluorescent antibody staining of smears and tissues, antigen detection in urine detection of lipopolysaccharide using specific monoclonal antibodies and PCR. Only PCR has gained widespread use. PCR is appealing because smears and cultures are usually negative, and organism isolation may be hazardous. Serological diagnosis may take weeks to confirm.

The one characteristic by which an unknown Cryptococcus species can be identified as Cryptococcus neoformans is: a appearance of yellow colonies b positive urease test c presence of a capsule d positive phenol oxidase test

d positive phenol oxidase test d Cryptococcus neoformans is the only clinically encountered yeast that is phenol oxidase positive.

A Gram stain of organisms on Loeffler agar showed pleomorphic gram-positive bacilli. The organism should be subcultured to: a blood b chocolate c MacConkey d potassium tellurite

d potassium tellurite d Media containing potassium tellurite is used for the recovery of Cory neb acterium diphtheriae.

The characteristic that is most commonly associated with the presence of strict anaerobic bacteria and can be taken as presumptive evidence of their presence in a clinical specimen is the: a presence of a single bacterial species b production of gas in a thioglycollate broth culture c growth on a blood agar plate incubated in an anaerobic jar d presence of a foul, putrid odor from tissue specimens and cultures

d presence of a foul, putrid odor from tissue specimens and cultures d Anaerobic bacteria characteristically produce foul-smelling metabolic end products.

A formed stool is received in the laboratory at 3 AM for ova and parasite exam. The night shift technologist is certain that the workload will prevent examination of the specimen until 6 AM when the next shift arrives. The technologist should: a request that a new specimen be collected after 6 AM b perform a zinc sulfate floatation procedure for eggs and hold the remaining specimen at room temperature c examine a direct prep for trophozoites and freeze the remaining specimen d preserve the specimen in formalin until it can be examined

d preserve the specimen in formalin until it can be examined d Formed stool is unlikely to contain trophozoites so direct examination of the stool is not necessary. The stool should be preserved as soon as possible to preserve any cysts, ova or larvae that may be present in the specimen.

A bronchial washing is processed for acid-fast bacilli. Which of the following precautions should be taken in order to prevent infection of laboratory personnel? a add an equal amount of NALC to the specimen b process all specimens under ultraviolet light c centrifuge specimen only after the addition of preservative d process all specimens in a biological safety hood

d process all specimens in a biological safety hood d Specimens processed for mycobacterial culture must be processed in a biological safety cabinet to minimize aerosol transmission of the organism.

Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species? a flagellar pattern b growth at 24°C c oxidase activity d rapid hydrolysis of urea

d rapid hydrolysis of urea d Both organisms are oxidase positive; Bordetella bronchiseptica is urea positive in 4 hours.

Members of the family Enterohacteriaceae share which one of the following characteristics? a produce cytochrome oxidase b ferment lactose c produce beta-hemolysis d reduce nitrate to nitrite

d reduce nitrate to nitrite d Members of Enterobacteriaceae are oxidase negative, ferment glucose, and reduce nitrate to nitrite.

In reviewing the number of Mycobacterium, isolates for the current year, it was noted that there were 76% fewer isolates than the previous year (115 vs 28). The technologist in charge of the area has documented that the quality control of media, reagents and stains has been acceptable and there has been no gross contamination of the cultures noted. The most appropriate course of action to pursue would be: a stop use of commercial media and produce in-house b change to different formulations of egg and agar based media c change over to the Bactec™ system for isolation of Mycobacterium d review the digestion and decontamination procedure

d review the digestion and decontamination procedure d The concentration of sodium hydroxide may be too strong due to decreased recovery of AFB and lack of contaminated cultures.

Characteristics necessary for the definitive identification of Mycobacterium tuberculosis are: a buff color, slow growth at 37°C, niacin production-positive, nitrate reduction-negative b rough colony, slow growth at 37°C, nonpigmented c rough, nonpigmented colony, cording positive, niacin production-negative, catalase-negative at pH 7/68°C d rough, nonpigmented colony, slow growth at 37 C, niacin production-positive, nitrate reduction-positive

d rough, nonpigmented colony, slow growth at 37 C, niacin production-positive, nitrate reduction-positive d Growth rate, colony morphology, niacin production, and nitrate reduction differentiate Mycobacterium tuberculosis from other mycobacteria.

A Staphilococcus aureus isolate has an MIC of 4ug/m: to axacillin. There is uncertainty as to whether this represents an oxacillin (heteroresistant) resistant strain or a hyperproducer of beta-lactamase. Strain Oxacillin Amoxicillin-clavulanic acid strand A Sus Sus stand B Sus Res strand C Res Sus strand D Res Res Based on the above results for oxacillin and amoxicillin, which strand is heteroresistant? a strand A b strand B c strand C d strand D

d strand D d A Staphylococcus aureus isolate with an MIC of 4 pg/mL is resistant to oxacillin.. As per the Clinical and Laboratory Standards Institute (CLSI) recommendations a heteroresistant strain would be defined as a methicillin (oxacillin) resistant S aureus (MRSA/ORSA). An MRSA/ORSA isolate would be reported as resistant to all beta lactam agents, beta lactam/beta lactamase inhibitor combinations, such as amoxicillin- clavulanic acid, and carbapenems.

The laboratory receives a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritis, and fatigue. The blood culture is positive after 5 days, and the organism has the following characteristics: Gram stain: small, gram-negative coccobacilli sheep blood agar: growth after 48 hours with small, smooth, raised colonies What should the microbiologist do next? a consider the growth contamination and perform another gram stain b perform biochemical identification for HACEK organisms c perform identification and susceptibility testing using an automated system d take extra safety precautions for possible Brucella

d take extra safety precautions for possible Brucella d Brucella causes undulant fever and is a cause of fever of unknown origin. It is slow growing, and is associated with laboratory- acquired infections. It is also a potential agent of bioterrorism. Suspected Brucella isolates should not be tested in automated or manual identification systems.

All species of the genus Neisseria have the enzyme to oxidize: a naphthylamine b dimethylaminobenzaldehyde c glucopyranoside d tetramethyl-phenylenediamine

d tetramethyl-phenylenediamine d Since all Neisseria species are oxidase positive, they possess the enzyme to oxidize tetramethyl-phenylenediamine.

Susceptibility testing is performed on a Staphylococcus aureus isolate from a blood culture with the following results: oxacillin: resistant cefazolin: susceptible clindamycin: susceptible erythromycin: susceptible trimethoprim/sulfamethoxazole: susceptible vancomycin: susceptible What should the technologist do next? a ceftriaxone should be reported instead of cefazolin b clindamycin should be tested for inducible resistance prior to reporting c the trimethoprim/sulfamethoxazole result should be removed since all S aureus are resistant d the cefazolin result should be changed to resistant since the oxacillin result is resistant

d the cefazolin result should be changed to resistant since the oxacillin result is resistant d Oxacillin resistant staphylococci are resistant to all beta-lactam agents, beta-lactam/beta-lactamase inhibitor combinations and carbapenems. Results for these antibiotics should be reported as resistant or should not be reported.

Vibrio parahaemolyticus can be isolated best from feces on: a eosin methylene blue (EMB) agar b Hektoen enteric (HE) agar c Salmonella Shigella (SS) agar d thiosulfate citrate bile salts (TCBS) agar

d thiosulfate citrate bile salts (TCBS) agar d TCBS is a highly selective and differential medium for the recovery of most Vibrio species including V parahaemolyticus. Hektoen and Salmonella-Shigella agars are selective and differential for the isolation and differentiation of enteric pathogens such as Salmonella and Shigella. EMB is a selective and differential medium for gram-negative enteric bacilli.

A community hospital microbiology laboratory is processing significant numbers of stool cultures because of an outbreak of diarrhea following heavy rains and flooding in the county. A media that should be incorporated in the plating protocol is: a colistin nalidixic acid for Listeria b MacConkey agar with sorbitol for Campylobacter c mannitol salt agar for Enterococcus species d thiosulfate citrate bile salts sucrose for Vibrio species

d thiosulfate citrate bile salts sucrose for Vibrio species d Thiosulfate citrate bile salt agar is a selective media for Vibrio, an it a so differentiates sucrose-fermenting species, such as Vcholerae and Valginolyticus.

The species of mycobacteria that will give a positive niacin test is Mycobacterium: a Leprae b kansasii c fortuitum d tuberculosis

d tuberculosis d A positive niacin reaction differentiates Mycobacterium tuberculosis from M leprae, M kansasii and M fortuitum.