CLS 251 Microbiology

Which one of the following organisms is commonly cultures from the nasopharynx of healthy people but is RARELY pathogenic: Select one: a. Beta hemolytic streptococci b. Corynebacterium species c. Haemophilus influenzae d. Neisseria meningitidis e. Staphylococcus aureus

b. Corynebacterium species

Stenotrophomonas maltophilia and Burkholderia cepacia share each of the following EXCEPT for which characteristic? a. Decarboxylation of lysine b. Cytochrome oxidase activity c. Production of colonies with a yellow pigment d. Good growth on MacConkey agar

b. Cytochrome oxidase activity Both produce yellow pigment colonies, grow on the MacConkey, and decarboxylation of lysine

Which of the following dematiaceous fungal species produce conidia in clusters? Select one: a. Alternaria species b. Exophiala species c. Cladosporium species

b. Exophiala species

Which of these laboratory methods are recommended for confirmation of influenza A H1N1 subtype infection? Select one: a. Immunofluorescence assay (IFA) b. Reverse transcriptase-polymerase chain reaction (RT-PCR) c. Rapid Influenza A/B test

b. Reverse transcriptase-polymerase chain reaction (RT-PCR)

Illustrated in the high power photomicrograph is a large 140 um ovum as it would appear in a stool specimen preparation. The adult flukes reside in the portal veins of the large intestine where ova are discharged into the lumen and into the feces. Low grade diarrhea may be experienced. From the multiple choices select the species of fluke related to this ovum. Select one: a. Schistosoma haematobium b. Schistosoma mansoni c. Fasciola hepatica d. Schistosoma japonicum

b. Schistosoma mansoni

Which of the following parasites enters its host through ingestion of infected pork? Select one: a. Schistosoma mansoni b. Trichinella spiralis c. Necator americanus d. Ascaris lumbricoides

b. Trichinella spiralis

________________ is predominantly associated with skin and soft tissue infections (SSTIs), such as abcesses, cellulitis, folliculitis and impetigo.

Community-associated MRSA

The trophozoite illustrated in the photograph is large, measuring 120 um, representative of what might be observed in a stool specimen obtained from an immune-compromised patient with low-grade diarrhea. Select from the multiple choice responses to derive a presumptive identification.

Balantidium coli

Illustrated in the upper composite photograph are non-hemolytic, smooth, entire non-pigmented white colonies growing on blood agar. Human isolates are most commonly from nosocomial infections related to endotracheal tubes and tracheostomies, with peritonitis inpatients receiving peritoneal dialysis. Distinctly light lavender-pink pigmented colonies are observed growing on MacConkey agar. Tiny coccobacilli simulating those of Neisseria species are observed in gram stains as illustrated in the lower photmicrograph. Other identifying features include the oxidative production acids from most carbohydrates (saccharolytic) and a negative oxidase test. From these observations, select from the multiple choices the presumptive identification of this isolate.

Acinetobacter baumannii

A major difference between Salmonella enterica and Shigella infections is that ONLY in salmonellosis can which of the following be observed?

Animals serve as a reservoir of infection.

Illustrated in the top image is a 10-day-old colony growing on the surface of Sabouraud Dextrose with Brain Infusion (SABHI) agar, incubated at 30 degrees C, recovered from an induced septum sample obtained from a 42-year-old Mid-western farmer. The colonies are not genus/species specific, and appear as a mold with a delicate, silky, cob-web like yellow-white mycelium. The species identification is made by observing the Lactophenol blue-stained tease mount preparation illustrated in the bottom image. With these observations, select the presumptive identification of this isolate from the choices shown below.

Blastomyces dermatitidis

Spinal fluid cultures on a 3-day-old infant revealed beta-hemolytic, Gram-positive cocci occurring in pairs and chains. The organism was catalase-negative and bile esculin-negative. Resistance to 0.04 U disk of bacitracin was noted. The other test necessary to identify this organism is a positive test by:

CAMP the case is typical of Streptococcus agalactiae(Group B strep). The main presumptive identification test is CAMP.

Except for its two day rapid growth on SABHI agar incubated at 30 C, the hair-like gray-white colony illustrated in the top photograph, consistent with a Zygomycete, was recovered in culture as an environmental contaminant of a skin ulcer. These species identification can be made from the lactophenol blue stained microscopic mount seen in the bottom photomicrograph. From these observations, select from the multiple choices the name of this isolate.

Circinella species

As a gram positive coccus, I've become a bit fancy Short chains and motile, plus I carry the gene VanC.

Enterococcus cassilflavus

The long, pencil-shaped, multi-celled, thin, and smooth-walled macroconidia illustrated in this image are characteristic of which species?

Exserohilum species

A 42-year-old chain smoker experienced an increase in cough, sputum production, and intermittent shortness of breath for over one week. A diagnosis of chronic bronchitis with acute exacerbation was made. The image shows a Gram stain of an early morning, spontaneously expectorated sputum. Based on the pleomorphic coccobacilli shown in the Gram stain, what is the most likely cause of the exacerbation?

Haemophilius influenza

An 87-year old patient had a foot wound that grew gram-negative rods on MacConkey agar as pink to dark pink oxidase-negative colonies along with the following results: TSI: A/A Indole: neg. MR: neg. VP: pos. Citrate: pos. H2S: neg. Urea: pos. Motility: neg. Ornithine: neg. Antibiotic susceptibility: Carboxicillin and ampicillin resistant, all others sensitive. What is the MOST likely organism?

Klebsiella pneumonia

A 30 year old Hispanic pregnant female developed fever and signs and symptoms of meningitis following ingestion of feta cheese sent by relatives in Mexico. The colonies recovered from a positive blood culture is shown in the upper photograph; the microscopic features in the lower photograph. The most likely identification is:

Listeria monocytogenes

The dematiaceous colony illustrated here grew to a diameter of 3-4 cm in 5 days. The dematiaceous fungus that can be ruled out is: Select one: a. Phialophora verrucosum b. Exserohilum species c. Alternaria species d. Ulocladium species

Phialophora verrucosum

On a plate growing S. pneumonia, the zone of inhibition around the disk shown in the image has been measured at 23 mm. Based on this result, you should:

Report oxacillin-susceptible

The ovum as illustrated in the high-power photomicrograph, averages 140 um. The ova are most commonly observed in a urine sediment from a patient complaining of frequent urination, dysuria, hematuria and recurrent urinary tract infections. Note the characteristic delicate, sharply pointed terminal spine (blue arrow) extruding from the anterior margin of the shell. From the multiple choices listed below, select the presumptive identification of this ovum.

Schistosoma haematobium

An infective agent of skin wound infections and an agent of toxic shock syndrome, the large, entire, golden-yellow, smooth convex colonies on blood agar were recovered from a swab specimen after 48 hours incubation at 37 degrees C. In the photomicrograph, clusters of gram-positive cocci were observed microscopically in a gram stain prepared from one of the colonies. The coagulase reactions are pictured in the lower images. With these observations, select the name of this isolate from the multiple choices as listed.

Staphylococcus aureus

The Optochin (ethylhydrocupreine hydrochloride) disc is MOST often used for the identification of which organism?

Streptococci pneumoniae

Tiny, gray-white colonies growing on the surface of chocolate agar were initially thought to be Haemophilus species. Consistent with this observation, streaks of colony growth had been observed adjacent to a beta hemolytic Staphylococcus test streak. A gram stain of this isolate is pictured here taken, from this blood agar plate. What presumptive identification can be made?

Streptococcus pneumonia CAMP test pos. Incorrect

In molecular diagnostic testing, hybridization employs complementary base pair binding of a synthetic strand to DNA or RNA Select one: True False

True Hybridization is a technique used to determine presence of target DNA or RNA by adding a synthetic strand that binds by complementary base pairing to the target.

Illustrated in the top photograph is a small circular white colony with a downy surface, recovered from a skin scraping specimen after 7 days of growth on agar supplemented with thiamine and inositol. The identification is made by observing the aerial hyphae (middle frame) and the underlying chains of pigmented chlamydospores among the hyphae (lower frame) as seen in this composite image. With these observations, select the identification of this dermatophyte.

Trichophyton tonsurans Incorrect

Select form the following choices the specimen that is inadequate for the recovery of anaerobes and should be summarily rejected upon receipt in the microbiology laboratory. Select one: a. Swab specimens taken from a deep sub-cutaneous abcess b. Needle aspirate in an anaerobic E-swab tube c. Syringe aspirate hand-carried to microbiology laboratory d. Uterine cervical swab in Cary-Blair transport medium

a. Swab specimens taken from a deep sub-cutaneous abcess

Select from the multiple choices the specimen that is inadequate for the recovery of anaerobes and should be summarily rejected upon receipt in the microbiology laboratory. Select one: a. Swab specimens taken from of deep sub-cutaneous abscess b. Needle aspirate in an anaerobic E-swab tube c. Syringe aspirate hand-carried to microbiology laboratory d. Uterine cervical swab in Cary-Blair transport medium

a. Swab specimens taken from of deep sub-cutaneous abscess Incorrect

I reside in the mouth where I measure approximately 17 micro meters. Select one: a. Entamoeba coli trophozoite b. Entamoeba gingivalis trophozoite c. Acanthamoeba species trophozoite d. Trichomonas vaginalis trophozoite

b. Entamoeba gingivalis trophozoite

Which two of the following organisms are gram-positive? Select one: a. Pasteurella b. Erysipelothrix c. Aeromonas d. Lactococcus

b. Erysipelothrix d. Lactococcus

Which one of the following organisms is sensitive to bacitracin: Select one: a. Group A Streptococcus b. Group B Streptococcus c. Group D Streptococcus d. Staphylococci

a. Group A Streptococcus

The colonies shown in the upper image were obtained on blood agar from a sputum specimen after 10 days incubation at 30° C. The lower image is a photomicrograph of a lactophenol blue mount made from a portion of the colony. The delicate cob-web appearance of the colonies on blood agar (upper image) and the production of macroconidia with a conspicuous prickly surface as seen in the lower image are characteristic of: Select one: a. Histoplasma capsulatum b. Coccidioides immitis c. Blastomyces dermatitidis d. Paracoccidiodes brasiliensis

a. Histoplasma capsulatum

The colonies shown in the upper image were obtained on blood agar from a sputum specimen after 10 days incubation at 30˚ C. The lower is a photomicrograph of a lactophenol blue mount made from a portion of the colony. The delicate cob-web appearance of the colonies on blood agar (upper image) and the production of macroconidia with a conspicuous prickly surface as seen in the lower image are characteristic of: Select one: a. Histoplasma capsulatum b. Coccidioides immitis c. Blastomyces dermatitidis d. Paracoccidiodes brasiliensis

a. Histoplasma capsulatum

Which substance acts as a mordant in the Gram Stain process? Select one: a. Acetone b. Crystal Violet c. Ethanol d. Iodine e. Safranin O

d. Iodine

Match the hepatitis B test with the appropriate disease phase. 1. HBsAg 2. Anti-HBs 3. Anti-HBc 4. Anti-HBc

1.Late incubation, acute 2.Recovery 3.Acute, convalescent 4.Acute, convalescent, recovery

If a Brucella species is suspected in a blood culture it should be held for a maximum of how many days on a commercial blood culture system?

10-14

Illustrated in the upper photograph of the composite is the surface of a blood agar plate on which small, entire, gray-yellow colonies are observed, with yellow pigmentation shown on the cotton swab. Light pink, non-fermentative colonies are seen on MacConkey agar (composite upper right), confirmed by the Alk/Alk reaction on KIA (left tube in composite lower image). Shown in this composite also are key reactions - positive lysine decarboxylase (center), and oxidative utilization of maltose and sucrose (right). This non-fermenter is most commonly an opportunistic pathogen in cases of respiratory infection associated with chronic granulomatous disease and cystic fibrosis. From these observations, select from the multiple choices the identification of this isolate.

Burkholderia cepacia

Minimum inhibitory concentration (MIC) susceptibility tests should be performed against other beta lactam antibiotics on important S. pneumonia isolates from blood cultures and other sterile body fluids when a MIC for penicillin is performed. Select one: True False

False The MIC susceptibility test results obtained for penicillin also are predictive for ampicillin, cefotaxime, imipenem, and other beta-lactam antibiotics, precluding the necessity for performing specific tests against these drugs.

A 21-year-old female developed painful swelling of the left knee associated with low grade fever. The knee was painful to palpitation, an effusion was evident, and the overlying skin was slightly erythematous. Fluid was aspirated and a direct Gram stain was performed (see image). Based on the Gram stain morphology, which of the following bacterial species is LEAST likely to serve as the etiologic agent in the case described?

Haemophilus influenza

The CAMP reaction is most helpful in the identification of n=beta hemolytic streptococci, group B (shown in the photograph as the arrowhead-shaped zone of the hemolysis at the tip of the red arrow). A beta hemolytic gram positive bacillus that produces the rectangular-shaped area of hemolysis as shown by the blue arrow in the photograph is:

Listeria monocytogenes Creates the rectangle on a CAMP test

The skin infection of the foot of a farmer as illustrated in the upper photograph was caused in a farmer when walking barefoot in soil contaminated with a filariform larva. Based on the morphology of the 50 um in diameter ovum (lower image), select from the question/answer list the species that is the presumptive cause of the infection.

Necator americanus

Small intracellular gram-negative cocci were observed in a centrifuged spinal fluid sediment as presented in the upper photomicrograph. A clinical diagnosis of meningitis was suspected. Yellow-gray colonies after 24-hour incubation had been observed on blood agar. Based on the carbohydrate utilization tube reactions observed in the lower photograph, select from the multiple choices the presumptive identification of this isolate.

Neiserria meningitidis Ferments glucose and maltose

The condition most likely to predispose a person to septicemia by viridans streptococci is:

Poor oral hygiene

HIV is known as a retrovirus because:

RNA is used as the template for DNA synthesis

This isolate is a catalase negative, gram positive coccus on sheep blood agar. The P disk has 5 ug of optochin and the zone around it is 16 mm. It has been streaked perpendicular to a beta lysine-producing Staphylococcus aureus. The presumptive identification is:

Streptococcus pneumoniae

The Epstein-Barr Virus is associated with which of the following conditions: Select one: a. Measles b. Burkitt's lymphoma c. Mumps d. Chicken pox

b. Burkitt's lymphoma

The most common rapid slide test (MONOSPOT©) for infectious mononucleosis employs: Select one: a. Horse erythrocytes b. Sheep erythrocytes c. Intact beef erythrocytes d. None of the above

a. Horse erythrocytes

Which bacterial species is a common agent of neonatal bacteremia? A. Streptococcus pyogenes B. Listeria monocytogenes C. Staphylococcus aureus D. Enterococcus faecium

B. Listeria monocytogenes Listeria are non-capsulated, non-acid-fast, ß-hemolytic, gram-positive bacilli that have a characteristic tumbling motility. They are found primarily in the environment and in the human GI tract. Since L. monocytogenes multiplies intracellularly, control of listeriosis requires cell-mediated immunity; thus, immunocompromised patients (such as newborns) are at high risk.

Illustrated in the top photograph are small, smooth, 48 hour old white yeast colonies growing on potato dextrose agar. The rudimentary spikes from the surface of the colonies (arrows) indicate that a germ tube test should be performed. The bottom image is the germ tube test for this isolate. Select from the multiple choices the identification of this yeast isolate.

Candida albicans

Observed in a stool specimen passed from a person with minor intestinal symptoms is an 8 um in diameter cyst as shown in the photomicrograph. Note the four nuclei and their distinctive blotlike karyosomes. Based on the microscopic appearance of this cyst, select from the list of answer choices the presumptive identification. Select one: a. Iodamoeba butschlii b. Chilomastix mesnili c. Entamoeba hartmanni d. Endolimax nana

Endolimax nana is the correct response. E. nana cysts are small, ranging from 6 - 8 um, and are characterized by the presence of four nuclei, each with a minute central karyosome surrounded by a clear space. Note that the nuclei are devoid of a ring of outer chromatin, referred to as "ball in socket".

Any laboratory that analyzes microbes or refers specimens that have the potential to contain microbial agents or toxins is a sentinel laboratory. Select one: True False

True

Which organism is a cell wall deficient bacterium that commonly causes atypical or "walking pneumonia?" Select one: a. Mycoplasma pneumonia b. Pneumocystis carinii c. Mycobacterium xenopi d. Bifidobacterium dentium

a. Mycoplasma pneumonia

Prior to receiving antibiotic therapy, a patient had a urinary tract infection with gram-negative, motile rods producing the following reactions: Indole: pos. H2S (TSI): pos. MR: pos. VP: neg. Phenylalanine deaminase: pos. Urea: pos. Citrate: pos. Ornithine decarboxylase: neg. Gelatin hydrolysis: pos. Based on the reactions above, what organism is MOST likely causing the infection? Select one: a. Proteus vulgaris b. Enterobacter cloacae c. Serratia marcescens d. Klebsiella pneumonia

a. Proteus vulgaris

The red ring at the top of the media in this tube indicates a positive indole reaction. The precursor substance in the medium from which the indole is produced is: Select one: a. Tryptophan b. p-dimethylaminobenzaldehyde c. Pyruvic acid d. Peptone

a. Tryptophan Indole, along with pyruvic acid and ammonia, are the chemical products resulting from the deamination of the amino acid tryptophan, under the action of the enzyme tryptophanase, produced by indole-positive bacterial species. P-dimethylaminobenzaldehyde is the reagent added to the incubated media to detect the presence of indole. As stated above, pyruvate is one of the byproducts along with indole in the deamination of tryptophan. Peptone is added to the medium as an enrichment for bacterial growth. Indirectly, if the peptone contains large quantities of tryptophan, it could serve as a source of indole production. Nevertheless, the intended answer here is tryptophan.

A gram-negative coccobacillus produces small gray colonies surrounded by a zone of hemolysis on a potato-blood-glycerol agar. The organism aslo grew on chocolate agar, but NOT on sheep blood agar. This is MOST likely to be which organism? Select one: a. Alcaliqenes fecalis b. Bordetella pertussis c. Franciscella tularensis d. Hemophilus influenza e. Yersinia pestis

b. Bordetella pertussis This bacterium grows well in glycerin-potato-blood agar of Bordet and Gengou and shows a slower growth pattern, usually requiring from 3 to 5 days after incubation. The colonies are beta-hemolytic, small and dome-shaped, possessing a gray metallic-look, sometimes similar to mercury droplets.)

The isolate is represented by the slow growing small, gray-white, opaque and non-hemolytic colonies on blood agar. Short, gram-negative bacilli are, lying singly but also in the form of characteristic "rosette-like" clusters (arrows) are observed in the lower photomicrograph. As additional biochemical reactions necessary to confirm a presumptive identification, oxidase and indole reactions are positive; catalase, nitrate and urease reactions are negative. Based on these observations, select from the multiple choices the presumptive identification of this isolate. Select one: a. Capnocytophaga canimorsus b. Cardiobacterium hominis c. Eikemella corrodens d. Kingella kingae

b. Cardiobacterium hominis

The infective stage for the majority of all intestinal amoebae is the: Select one: a. Trophozoite b. Cyst c. Larva d. Egg

b. Cyst

Which two of the following organisms are gram-positive? Select one or more: a. Pasturella b. Erysipelthrix c. Aeromonas d. Lactococcus

b. Erysipelthrix d. Lactococcus

A one of the morphological families of parasites, features that characterize various Nematode species include: Select one: a. Disease may be transmitted via a direct fecal to oral route b. Filariform larvae may serve as an infective form for humans c. Both A and B d. None of the above

c. Both A and B

A recto-sigmoidoscopy revealed pseudomembranes in a patient with severe diarrhea following prolonged treatment with ampicillin. Which of the following organisms is MOST likely to be isolated? Select one: a. Bacteroides fragilis b. Clostridium botulinum c. Clostridium difficile d. Fusobacterium nucleatum e. Klebsiella oxytoca

c. Clostridium difficile Clostridium difficile is a gram-positive, anaerobic, spore-forming bacillus that produces a strong toxin. C difficile is a common cause of antibiotic-associated diarrhea and pseudomembranous colitis.

The well circumscribed cutaneous papule with the distinct outer erythematous border illustrated in the upper photograph developed over a period of 5 days at the site of a tick bite. The lower photograph illustrates colonies growing on a buffered charcoal yeast extract agar plate that had been inoculated with material from the ulcer bed three days before. Tiny, pale-staining gram negative coccobacilli were seen on a gram stain. The most likely causative agent is: Select one: a. Bacillus anthracis ("malignant pustule") b. Erysipelothrix rhusiopathiae c. Francisella tularensis d. Streptococcus pyogenes (pyoderma)

c. Francisella tularensis

Which one of the following statements is true regarding the 2009 H1N1 virus? Select one: a. Novel 2009 H1N1 virus is an influenza B virus b. Novel 2009 H1N1 virus only infects pigs and horses c. In 2009, the novel H1N1 virus spread during warmer months

c. In 2009, the novel H1N1 virus spread during warmer months

Under a Woods' lamp, infected hair strands from several children with tinea capitis showed green fluorescence, and subsequent cultures grew fungi with aerial mycelia and terminal chlamydospores. These isolates are most likely: Select one: a. Candida albicans b. Epidermophyton floccosum c. Microsporum audouinii d. Microsporum gypseum e. Trichophyton rubrum

c. Microsporum audouinii

Small, gray-white colonies, as observed growing on 7-H10 agar to the left in the upper composite photograph, were recovered from an upper respiratory specimen after 7 days incubation. This Mycobacterium species in the pas was uncommonly recovered from human infections until the advent of AIDS when it became an agent of pulmonary and other infections. Notably, colony isolates from patients with AIDS have developed a pale yellow pigmentation that does not intensify with light exposure (right image in upper composite photograph). The acid-fast bacilli as observed in the lower photomicrograph are short and lie singly or in loose clusters. From these observations select from the multiple choices the presumptive identification of this isolate. Select one: a. Mycobacterium marinum b. Mycobacterium tuberculosis c. Mycobacterium avium/intracellulare d. Mycobacterium kansasii

c. Mycobacterium avium/intracellulare

Which one of the following does NOT have capsular material as a defense mechanism? Select one: a. H. influenza b. K. pneumonia c. N. meningitides d. S. aureus e. S. pneumonia

d. S. aureus This capsular material is an antiphagocytic substance which helps deter bacterial death by macrophages and other white blood cells.

Surprise! Animals are not the only creatures infected with bacteria. The bacterial species causing onion rot is: Select one: a. Shewanella putrifaciens b. Burkholderia cepacia c. Pantoea agglomerans (Erwinia herbicola) d. Klebsiella planticola

c. Pantoea agglomerans (Erwinia herbicola) Incorrect

An isolate of S. pneumoniae from a respiratory specimen gave a zone of inhibition of 18 mm aroung a 1 ug oxacillin using the disk diffusion test. What should the next step be? Select one: a. Report the isolate as penicillin sensitive b. Report the isolate as penicillin resistant c. Set up an MIC on the isolate d. Report the isolate as moderately susceptible

c. Set up an MIC on the isolate

The combination of organisms that is correctly paired with the reactions for appropriate quality control (one organism positive for the reaction and one organism negative for the reaction) are: Select one: a. Coagulase: Staphylococcus saprophyticus and Staphylococcus epidermidis b. H2S production: Proteus mirabilis and Salmonella c. Phenylalanine deamination: Escherichia coli and Yersinia enterocolytica d. Indole: Escherichia coli and Proteus mirabilis

d. Indole: Escherichia coli and Proteus mirabilis

Fluorometers are designed so that the path of the excitation light is at a right angle to the path of the emitted light. What is the purpose of this design? Select one: a. Prevent loss of emitted light b. Prevent loss of the excitation light c. Focus emitted and excitation light upon the detector d. Prevent excitation light from reaching the detector

d. Prevent excitation light from reaching the detector

Multiple young 3-day old colonies having a low cottony surface mycelium that upon maturity develop a distinctly gray pigmentation (referred to as "house mouse gray"). The reverse of the colony remains light gray in color and does not show the darker pigmentation. Microscopic examination of a small inoculums from the surface of the colony is illustrated in the lower photomicrograph. From the list of multiple choices, select the genus name of the fungus being represented. Select one: a. Beauveria b. Sepedonium c. Chrysosporium d. Scedosporium

d. Scedosporium

As one of the aerobic actinomycetes, the light yellow, entire, convex, smooth, non hemolytic colonies is observed on blood agar. The gram stain, showing gram-positive bacilli, with filamentous forms seen in younger cultures, is not distinctive. Key to the identification is the hydrolysis of casein, as seen in the lower photograph. Xanthine was not hydrolyzed. The presumptive identification is: Select one: a. Rhodococcus equi b. Nocardia asteroides c. Oerskovia turbata d. Streptomyces species

d. Streptomyces species Incorrect

Which of the following does not pose a significant risk of transmitting bloodborne pathogens? Select one: a. Bloody urine b. Semen c. Pleural fluids d. Sweat

d. Sweat

The target cell of the AIDS virus is the: Select one: a. B lymphocyte b. Erythrocyte c. Granulocyte d. T lymphocyte e. Histiocyte

d. T lymphocyte

The end product of the fermentative metabolism that characterizes members of the Enterobacteriaceae is: Select one: a. CO2 and water b. Nitrogen gas c. Pyruvic acid d. Various mixed acids

d. Various mixed acids Although the fermentation of glucose passes through pyruvic acid as a pivotal compound, the end products of fermentative metabolism are the mixed acids such as acetic, formic, butyric, propionic, etc. The production of these acids is responsible for the conversion of the color of Kligler iron agar (pink to yellow) that is common to all members of the Enterobacteriaceae. CO2 and water are the end products of oxidative metabolism. Nitrogen gas is formed from the complete denitrification of nitrates or nitrites.

Compared to blood agar media, chocolate blood agar FAVORS the growth of which organisms? Select one: a. anaerobic bacteria b. facultative anaerobes c. all gram-positive bacteria d. more fastidious bacteria e. hemolytic bacteria

d. more fastidious bacteria

Illustrated in this photograph is a sulfide indole motility (SIM) tube (left) and an esculin hydrolysis slant (right) after inoculation with an unknown gram positive bacillus and incubation at 30 degrees C for 24 hours. Based on the reactions observed, the most likely identification is

Listeria monocytogenes: umbrella motility in tube, gram + rod, esculin hydrolysis pos. SIM tubes test for 3 things: (1) hydrogen sulfide production (2) indole production, and (3) motility. If an organism produces the enzyme tryptophanase, it will degrade tryptophan into indole, pyruvate, and ammonia. If indole is produced it will appear red. Organisms which produce the enzyme thiosulfate reductase can reduce sulfur to hydrogen sulfide gas. In the SIM deep tubes, the source of sulfur is sodium thiosulfate. If hydrogen sulfide gas is produced, it reacts with ferrous sulfate, giving a black precipitate. Organisms which are motile will exhibit diffuse growth that spreads out from the initial stab line, whereas organisms which are not motile will only grow where the agar was initially stabbed. The purpose of a esculin hydrolysis slant is to see if the microbe can hydrolyze the compound esculin as a carbon source. When microbes metabolize esculin in a nutrient medium, the dark brown compound esculetin is produced

The entire, smooth, convex Mycobacterium species colonies growing on 7H10 agar were observed to be dark yellow pigmented early in culture even before having been exposed to light. This isolate was found to be Tween-80 positive as seen in the reaction tubes in the bottom photograph. Select from the multiple choices the presumptive identification of this isolate. a. Mycobacterium gordonae b. Mycobacterium fortuitum c. Mycobacterium kansasii d. Mycobacterium marinum

a. Mycobacterium gordonae Tween 80 is a detergent. Some Mycobacterium species posses an enzyme-lipase, that splits the compound and releases oleic acid and polyoxyethylated sorbitol.The color change from orange yellow to red is the positive test. This test is useful in identifying Mycobacterium kansasii (which can produce positive results within 3-6 hours). Test is used mainly to differentiate slow-growing Mycobacterium (Scotochromogens) with similar colony appearance, M. gordonae (positive) and M. scrofulaceum (negative). When grown in the dark M. kansasii colonies are at first non-pigmented but turn yellow after exposure to light.

Which one of the following results is typical of Campylobacter fetus subspecies jejuni? Select one: a. Optimal growth at 42 degrees C b. Oxidase negative c. Catalase negative d. Nonmotile e. Best growth at room temperature

a. Optimal growth at 42 degrees C

An infective agent of skin wound infections and an agent of toxic shock syndrome, the large, entire, golden-yellow, smooth convex colonies on blood agar were recovered from a swab specimen after 48 hours incubation at 37 degrees C. In the photomicrograph, clusters of gram-positive cocci were observed microscopically in a gram stain prepared from one of the colonies. The coagulase reactions are pictured in the lower images. With these observations, select the name of this isolate from the multiple choices as listed. a. Staphylococcus aureus b. Staphylococcus saprophyticus c. Micrococcus luteus d. Staphylococcus epidermidis

a. Staphylococcus aureus

A small gram-negative rod isolated from an eye grows on chocolate agar but NOT on sheep blood agar. It produces satellite growth around staphylococci on sheep blood agar, however. The organism requires: Select one: a. X and V factor b. X factor only c. V factor only d. Neither X or V factor

a. X and V factor

The lecithin hydrolysis, indicated by the tips of the arrows in this photograph of an egg yolk agar plate, may be produced by each of the following Bacillus species except: Select one: a. Bacillus cerebus b. Bacillus subtilis c. Bacillus mycoides d. Bacillus anthracis

b. Bacillus subtilis

If CFS tubes numbered #1, #2, and #3 CANNOT be analyzed within one hour, the correct procedure for the microbiology sample tubes is to: Select one: a. Refrigerate it b. Freeze it c. Leave it at room temperature d. Incubate in a 56 degree water bath

c. Leave it at room temperature

The colonies illustrated in the composite blood agar/MacConkey agar to the left were recovered from an inflammatory infection of the oral cavity of a 16-year-old student. The colonies on both agar plates incubated anaerobically are small, entire, and smooth with a light gray-yellow pigmentation. Small gram-negative rods arranged singly and in loose clusters had been observed microscopically in a gram-stained preparation. Spot indole and lipase reactions are positive. Note in the image to the right the alk/alk non-fermentative carbohydrate reaction on Kligler Iron agar, with lack of fermentation of the sugars presented in the tub es to the right (asaccharolytic). Select from the multiple choices the name of this anaerobic, asaccharolytic, gram-negative isolate. Select one: a. Porphyromonas asaccharolytica b. Fusobacterium nucleatum c. Bacteroides fragilis d. Propionibacterium acnes

b. Fusobacterium nucleatum Incorrect

Detection of antigens in clinical specimens when parasites are observed in stool specimens is the current test of choice for identification when a diagnosis is in doubt, providing an increased sensitivity over more common microscopy techniques. Several commercial products (DFAs, EIAs, and rapid tests) are available. Illustrated in the photomicrograph is an H & E - stained tissue section of duodenum illustrating the presence of an intra-luminal intestinal trophozoite in which an antigen assay of duodenal fluid might be helpful in making a definitive identification. Select from the multiple choices the presumptive identification. Select one: a. Chilomastix mesnili b. Giardia duodenalis c. Dientamoeba fragilis d. Trichomonas hominis

b. Giardia duodenalis

Which one of the following descriptions about Pasturella is FALSE? Select one: a. Forms large amounts of indole. b. Grows well on MacConkey agar. c. Many infections caused by domesticated animals. d. Multocida is species most frequently isolated from humans. e. Produces an odor similar to E. coli.

b. Grows well on MacConkey

The presumptive diagnosis of fungal infections mey be made based on the location of sites of visit in which they became endemic. One such condition, is colloquially referred to as "Spelunker's Scourge". This condition occurs after a tour or work in underground caves located in the Midwest, where dust contaminated with bird and bat dung is inhaled. Select the name of the fungus from the choices shown below that causes this endemically-acquired respiratory infection. Select one: a. Coccidioides immitis b. Histoplasma capsulatum c. Blastomyces dermatitidis d. Paracoccidioides brasilienses

b. Histoplasma capsulatum

Which of the following statements concerning C. difficile is NOT true? Select one: a. It is the causative agent of an inflammatory condition of the large intestine. b. It is an aerobic organism. c. It produces potent toxins. d. It produces spores.

b. It is an aerobic organism.

What is the probable identity of an organism isolated from a wound culture that demonstrates the following test results? Phenylalanin Deaminase = negative TSI - A/A gas Citrate = positive Lysine = positive SIM = negative/negative/negative Urea = weakly positive Select one: a. Escherichia coli b. Klebsiella pneumoniae c. Enterobacter aerogenes d. Proteus vulgaris e. Salmonella spp.

b. Klebsiella pneumoniae

Illustrated in this photograph are two Middlebrook 7H-11 plates incubated at 35 degrees C, on which are growing colonies of an unknown Mycobacterium species. The plate on the left was incubated in the dark; the plate at the right had been exposed to light for 24 hours. The most likely identification is: Select one: a. Mycobacterium gordonae b. Mycobacterium kansasii c. Mycobacterium tuberculosis d. Mycobacterium marinum

b. Mycobacterium kansasii

Illustrated in the photograph are 14 day-old colonies of a Mycobacterium species growing on Middlebrook 7H-10 agar, with development of yellow pigmentation after exposure to environmental light. From the choices listed below, select the correct presumptive identification of this photochromogenic Mycobacterium species. Select one: a. Mycobacterium chelonae b. Mycobacterium marinum c. Mycobacterium scrofulaceum d. Mycobacterium gordonae

b. Mycobacterium marinum Runyon I organisms (photochromogens) are slow growing, and produce a yellow-orange pigment when exposed to light. The group includes Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium asiaticum, and Mycobacterium simiae

The increased resistance of MRSA strains to beta-lactam antibiotics is due to production of which of the following penicillin binding proteins (PBPs)? Select one: a. PBP 2 b. PBP 2a c. PBP 3 d. PBP 4

b. PBP 2a The beta-lactam resistance of MRSA is determined by the production of a novel penicillin-binding protein called PBP 2a (PBP 2'), that has a reduced binding affinity for beta-lactam antibiotics. This allows MRSA strains to continue cell wall synthesis due to the uninhibited activity of PBP2a even in the presence of otherwise inhibitory concentrations of beta-lactam antibiotics. The mecA gene encodes the production of PBP 2a. S. aureus intrinsically produces beta-lactamase enzymes that break down beta-lactam antibiotics; these are designated PBP 1 - 4.

A 40-year-old business man developed intermittent spiking fevers one week following a trip to Western Africa. The Wright-stained peripheral blood smear as illustrated in the image was observed. Based on the morphology of the erythrocytes and the heavy invasion with ring form trophozoites, the diagnosis of malaria could be made. With particular focus on the sickle-form gametocyte, which Plasmodium species is represented by the peripheral blood smear? a. Plasmodium vivax b. Plasmodium falciparum c. Plasmodium malariae d. Plasmodium ovale

b. Plasmodium falciparum

Illustrated in the photomicrograph is the tail portion of an adult worm of a filarial nematode as it may be observed in a peripheral blood smear. These worms measure up to 300 um in length and commonly inhabit the lymphatics. This nematode species more commonly inhabit the lymphatics. This nematode species more commonly involves the lymphatics of the inguinal region resulting in swelling below the knee in what is known as "elephantiasis". The species indicated in this exercise can be presumptively determined by the orientation of the nuclei within the tail section (arrows). From the nematode species listed below, indicate the most likely species identification. Select one: a. Brugia malayi b. Wuchereria bancrofti c. Loa loa d. Dirofilaria immitis

b. Wuchereria bancrofti Incorrect

Which of the following would be the most appropriate temperature for long term storage of viral cultures: Select one: a. 4° C b. -20° C c. -70° C d. Room temperature

c. -70° C

Based on the structures observed in this photomicrograph, the most probable species of the fungus recovered from an induced sputum specimen is Select one: a. Aspergillus fumigatus b. Aspergillus niger c. Aspergillus nidulans d. Aspergillus flavus

c. Aspergillus nidulans

An abdominal wound culture grows E. coli on the aerobic culture. The anaerobic culture has growth of two gram negative rods, one of which is aerobic. The other gram negative rod has 2+ growth on BBE plate and is resistant to Kanamycin, Colistin, and Vancomycin disc. This organism can be identified as: Select one: a. Veillonella b. Prevotella fragilis c. Bacteroides fragilis group d. Fusobacterium necrophorum

c. Bacteroides fragilis group Bacteroides Bile Esculin Agar (BBE) is an enriched selective and differential medium for the isolation and presumptive identification of obligately anaerobic gram-negative bacilli of the Bacteroides fragilis group. BBE contains gentamicin at a concentration which inhibits most facultative anaerobes. With a few exceptions, Bacteroides species are resistant to kanamycin and vancomycin and show variable susceptibility to colistin.

The media used to isolate Legionella pneumophilia should contain which of the following additives? Select one: a. X and V factors b. Hemin and vitamin K c. Charcoal and yeast extract d. Dextrose and laked blood e. Lactose and vitamin E

c. Charcoal and yeast extract

Within three days at 28°C a sputum specimen placed in Sabouraud's dextrose agar with chloramphenicol and cycloheximide produced moist, grayish growth, with a white aerial mycelium, the organism is MOST likely: Select one: a. Asperigillus fumigatus b. Blastomyces dermatitidis c. Coccidioides immitis d. Cryptococcus neoformans e. Histoplasma capsulatum

c. Coccidioides immitis Incorrect

A recto-sigmoidoscopy revealed pseudomembranes in a patient with severe diarrhea following prolonged treatment with ampicillin. Which of the following organisms is MOST likely to be isolated? Select one: a. Bacteroides fragilis b. Clostridium botulinum c. Costridium difficile d. Fusobacterium nucleatum e. Klebsiella oxytoca

c. Costridium difficile gram-positive, anaerobic, spore-forming bacillus that produces a strong toxin. C difficile is a common cause of antibiotic-associated diarrhea and pseudomembranous colitis

Who am I, here in this mush, Looking like a test tube brush? Select one: a. Listeria monocytogenes b. Pseudomonas fluorescens c. Erysipelothrix rhusiopathiae d. Enterococcus cassiflavus

c. Erysipelothrix rhusiopathiae

A 20-year-old female was admitted into the hospital complaining of 10 to 15 bloody mucous stools per day, fever, gastrointestinal disturbances, abdominal pain, and nausea. The preliminary O & P report went out as "Probable Entamoena histolytica trophozoites and cysts, confirmations pending." What is the patient most likely suffering from? Select one: a. Traveler's diarrhea b. Extraintestinal amebiasis c. Intestinal amebiasis d. Giardiasis

c. Intestinal amebiasis

Illustrated in this exercise are colonies growing on Middlebrook 7H10 agar before (left) and after (right) exposure to light. Colonies are intermediate between smooth and rough depending on the strain. Prior to exposure to light the colonies are gray white. Upon exposure to ambient light, visible yellow pigment production is observed characteristic of one of the "photochromogens", as illustrated in the top composite colony photograph, The acid-fast stain reveals slender acid fast bacilli with cross banding. Characteristic for the presumptive identification of this isolate are positive reactions for several biochemical reactions - nitrate reduction, Tween 80 hydrolysis, catalase, urease and pyrazinamidase. With these observations, select from the multiple choices the species name of this isolate. Select one: a. Mycobacterium scrofulaceum b. Mycobacterium avium-intracellulare c. Mycobacterium kansasii d. Mycobacterium fortuitum

c. Mycobacterium kansasii

Illustrated in the top mage are colonies after 12 days of incubation of a Mycobacterium specied that developed a yellow pigmentation upon exposure to light (photochromagen). A positive niacin accumulation reaction is shown in the lower image suggestive of M. tuberculosis, a species that can be ruled out because of the colony pigment production. From the multiple choices, select the name of this photochromogenic Mycobacterium species. a. Mycobacterium gordonae b. Mycobacterium scrofulaceum c. Mycobacterium simiae d. Mycobacterium chelonae

c. Mycobacterium simiae Runyon I organisms (photochromogens) are slow growing, and produce a yellow-orange pigment when exposed to light. The group includes Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium asiaticum, and Mycobacterium simiae.

The bacterial species shown in this composite photograph of a chocolate agar plate and accompanying gram stain, recovered from an autopsy blood culture of a patient dying with Waterhouse Friderichsen syndrome is most likely: Select one: a. Moraxella catarrhalis b. Neisseria gonorrhoeae c. Neisseria meningitidis d. Acinetobacter baumannii

c. Neisseria meningitidis Waterhouse-Friderichsen syndrome (WFS) is defined as adrenal gland failure due to bleeding into the adrenal glands, commonly caused by severe bacterial infection: Typically it is caused by Neisseria meningitidis.

Each of the following properties inherent in a bacterium contribute to the virulence except: Select one: a. Presence of a polysaccharide capsule b. Production of a proteolytic enzymes c. Production of opsonins d. Presence of surface membrane attachment receptors

c. Production of opsonins

Sodium thiosulfate is often added to selective culture media to: Select one: a. Inhibit the grow of gram positive bacteria b. Detect hydrogen sulfide c. Provide sulfur atoms for H2S positive isolates d. Serve as a pH buffer

c. Provide sulfur atoms for H2S positive isolates Sodium thiosulfate serves as the electron receptor for reduction of sulfur and production of h2s. 6. Detects fermentation of sucrose, lactose, glucose, as well as production of hydrogen sulfide and /or gas.

The test used for the indentification of specific capsular serotypes of Streptococcus pneumonia is: Select one: a. Optochin b. Bile solubility c. Quellung d. Hippurate hydrolysis

c. Quellung antibodies bind to the bacterial capsule of Streptococcus pneumoniae. These species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge or swell.

If a CAMP test had an arrowhead appearance, the bacitracin disk had a zone of 6 mm with a 6 mm disk, the bile esculin was tan throughout, and the SXT disk had a zone of 6 mm with a 6 mm disk, the action you should take would be: Select one: a. Identify the isolate as Group A Streptococcus b. Repeat the SXT test because it should not have a zone. c. Report the isolate as Beta streptococcus Group B d. Perform a 6.5% NaCL tolerance test to rule out Enterococcus species

c. Report the isolate as Beta streptococcus Group B

In the photgraph to the left is shown a 4 day old colony grown on Sabouraud's Dextrose agar. It was recovered from what was considered a "contaminant" from a bacterial culture. The image to the right was is a high power photomicrograph of a methylene-blue stained mount prepared from the surfaces of the colony. With these observations, select the fungus genus from the multiple choices as listed. Select one: a. Scedosporium b. Chrysosporium c. Sepedonium d. Beauveria

c. Sepedonium Incorrect

The dimorphic fungus that may produce black, yeast-like colonies after prolonged incubation at 37˚ C is: Select one: a. Blastomyces dermatitidis b. Paracoccidioides brasiliensis c. Sporothrix schenckii d. Histoplasma capsulatum

c. Sporothrix schenckii

Observe the Optochin "P" disc reaction illustrated in the upper left photograph on the surface of blood agar. Heavy growth of tiny, alpha hemolytic colonies are observed growing on the agar surface that extend to the outer margins of the paper disc. The gram stain presented in the lower photomicrograph reveals small gram-positive cocci lying singly, in small clusters, and more typically in long chains. This isolate has been recovered from blood cultures in cases of post-valvular endocarditis. From the list of multiple choices, select the presumptive identification of this isolate. a. Streptococcus pneumoniae b. Streptococcus agalactiiae c. Streptococcus viridans d. Streptococcus anginosus

c. Streptococcus viridans

The federal government has categorized critical biological agents into three groups: A, B, and C. Why are the agents in category A classified as the highest priority? Select one: a. These organisms cause moderate morbidity and low mortality b. These organisms could be engineered for mass dissemination at some future date. c. These organisms can be easily disseminated or transmitted person-to-person.

c. These organisms can be easily disseminated or transmitted person-to-person.

The fastidious gram negative bacillus featured here has been recovered from individuals in pandemic outbreaks of diarrhea after ingestion of contaminated stream, lake, or well water. In many cses, life-threatening profuse diarrhea resulting in dehydration and electrolyte loss is often experienced. Smooth, entire, convex light gray yellow colonies are observed on blood agar (left upper image). Note the yellow pigmentation of the colonies growing on TCBS agar (Thiosulfate Citrate Bile Sucrose) on the right of the composite image, indicating strong acid production from sucrose. Cytochrome oxidase is also positive. Small, curved and S-shaped, gram-negative bacilli are seen on Gram stain. From these observations, select from the multiple choices the correct genus/species identification of this isolate. Select one: a. Aeromonas hydrophila b. Plesiomonas shigelloides c. Vibrio cholerae d. Non-Vibrio cholera

c. Vibrio cholerae The bile salts inhibit growth of gram-positive microorganisms; one percent sodium chloride is incorporated into the medium to provide optimum growth and metabolic activity of halophilic Vibrio spp.; sodium thiosulfate provides a source of sulfur and also acts in combination with ferric citrate to detect the production of hydrogen sulfide; sucrose serves as the fermentable carbohydrate that, with the help of bromothymol blue and thymol blue indicators, allows for the differentiation of those Vibrio spp. which utilize sucrose.

In order to speciate a swarming Proteus organism found on an eosin methylene blue agar plate, the BEST approach would be to: Select one: a. inoculate to a 4% agar plate and subculture to McConkey's b. determine motility and lysine decarboxylase activity c. determine Indole production, phenylalanine and urease activity d. determine utilization of sodium acetate and citrate e. inoculate a tube of thioglycolate broth

c. determine Indole production, phenylalanine and urease activity P. mirablis is strongly urease and phenylalanine positive. P. mirabilis is usually indole-negative- which is helpful to differentiate this organism from P. vulgaris which is indole-positive.

The fungus illustrated in this photomicrograph was recovered from an induced sputum specimen from a 74 year old man with chronic obstructive pulmonary disease. This isolate is most likely: Select one: a. The cause of chronic bronchitis b. The cause of invasive pulmonary disease c. The cause of allergic bronchopulmonary disease d. A contaminant

d. A contaminant if a patient does not have underlying immunologic or hematologic disease, Scopulariopsis species should be considered a contaminant when recovered from a sputum specimen. If Scopulariopsis species or any other hyaline mold is recovered from two or more successive specimens, its potential as a pathogenic agent should be considered.

The entire, smooth, golden yellow-pigmented non-hemolytic colonies on the surface of the blood agar plate seen in the upper image have been recovered in hospital acquired infections from patients with cystic fibrosis. A Gram stain prepared from one of the colonies as shown in the lower image, reveal long, narrow gram-negative bacilli arranged singly. Polar flagella would be seen in flagellar stains. All carbohydrate reactions are negative except for the oxidative utilization of maltose. Positive biochemical reactions for DNA'se and for esculin assist in making a definitive identification. Based on these observations, select from the multiple choices the identification of this isolate. a. Burkholderia cepacia b. Stenotrophomonas maltophilia c. Flavobacterium meningosepticum d. Bordetella bronchiseptica

d. Bordetella bronchiseptica Incorrect

Each of the following characteristics will differentiate between Listeria monocytogenes and Erysipelothrix rhusiopathiae except: Select one: a. Hydrolysis of esculin b. Motility c. Catalase d. Fermentation of glucose

d. Fermentation of glucose Listeria is catalase positive, motile, hydrolysis of esculin positive

Which one of the following comments about Francisella is not true? Select one: a. Can penetrate minute skin breaks b. Causes Tularemia c. Possesses a thin capsule d. Is a strict anaerobe e. Transmitted by tick bites

d. Is a strict anaerobe it is a strict aerobe

Illustrated in these paired photomicrographs are acid fast stains of tissue sections of colon obtained from an AIDS patient with chronic diarrhea, illustrating a heavy infiltration with acid-fast bacilli (upper image), literally engorging the submucous macrophages (lower image). The MycobacteriumI species most commonly associated with this infection is: Select one: a. Mycobacterium gordonae b. Mycobacterium tuberculosis c. Mycobacterium bovis d. Mycobacterium avium intracellulare complex

d. Mycobacterium avium intracellulare complex

The adult fluke related to the 100 um ovum, as illustrated in the image shown, most commonly inhabits the lung parenchyma. The ovum, as may be observed in a sputum specimen, has a smooth, slightly thickened shell with a prominent shouldered operculum as seen at the left lower end. A developing larvae is observed within, retracting from the inner marginof the shell leaving a clear space. Infections with this fluke are endemic in the orient, in West Africa, in South and Central America and may be observed in patients elsewhere after travel to one of these regions. Humans become infected after ingestion of poorly cooked crab meat or crayfish contaminated with metacercariae. Intermittent chest pain, and cough with occasional spitting up of blood (hemoptysis) may be experienced after infection. From the choices below, select the trematode species related to this ovum. Select one: a. Clonorchis sinensis b. Fasciola hepatica c. Fasciolopsis buski d. Paragonimus westermani

d. Paragonimus westermani

The observation of darkly pigmented colonies on blood agar as illustrated in this photograph is somewhat of a surprise. The colonies of each of the following bacterial species may have an appearance similar to that seen here except: Select one: a. Prevotella melaninogenica b. Stentotrophomonas maltophilia c. Chromobacterium violaceum d. Pseudomonas aeruginosa

d. Pseudomonas aeruginosa Incorrect