Microbiology Certification Exam
An organism was isolated on kanamycin-vancomycin agar from a peritoneal abscess. The genus of this organism most likely is:
Bacteroides
Which of the following anaerobes would be positive for indole?
Bacteroides thetaiotaomicron
A culture from an infected dog bite on a small boy's finger yielded a small, gram-negative coccobacillus that was smooth, raised, and beta-hemolytic on blood agar. The isolate was found to grow readily on MacConkey agar forming colorless colonies. The organism was motile with peritrichous flagella, catalase positive, oxidase positive, reduced nitrate, utilized citrate, and was urease positive within 4 hours. No carbohydrates were fermented. The most likely identification of this isolate is:
Bordetella bronchiseptica
The reverse CAMP test, lecithinase production, double zone hemolysis, and Gram stain morphology are all useful criteria in the identification of:
Clostridium perfringens
Staib's medium (Niger seed agar) is useful in the identification of which of the following?
Cryptococcus neoformans
Which feature distinguishes Erysipelothnix rhusiopathiae from other clinically significant non—spore-forming, gram-positive, facultatively anaerobic bacilli?
H2S production
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 an atmosphere of 5% CO2. Which of the following organisms would usually be isolated by this procedure?
Haemophilus influenzae
An organism that exhibits the satellite phenomenon around colonies of staphylococci is:
Haemophilus influenzae
Items to consider when using the staphylococcal coagglutination procedi
Hyperproteinemia may cause autoagglutination and thus false-positive results
A technologist repeatedly misses tubercle bacillli when examining stained smears for fast bacilli. What plan of action should the supervisor FIRST take to correct this problem?
Review the diagnostic criteria with the emplyoee and monitor progress.
Which of the following tests is used to monitor bactericidal activity during antimicrobic therapy in cases of endocarditis?
Schlichter
The stock cultures needed for quality control testing of deoxyribonuclease (DNAse) production are:
Serratia marcescens/Escherichia coli
Which of the following genera is among the least biochemically reactive members of the Enterobacteriaceae?
Shigella
A mold grown at 25C exhibited septate hylaine hyphae and many conidiophores extending at right angles from the hyphae. Oval, 2- to -5um 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 37C culture of this organism produced small, cigar-shaped yeast cells. This organism is most likely:
Sporothrix schenckii
Of the following bacteria, the most frequent cause of prosthetic heart valve infections occurring within two to three months after surgery is:
Staphylococcus epidermidis
The optochin (ethylhydrocupreine hydrochloride) disk is used for the identification of:
Streptococcus pneumoniae
The term "internal autoinfection" is generally used in referring to infections with:
Strongyloides stercoralis
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 mold phase, which was isolated at room temperature on Sabouraud's dextrose agar containing chlorainphenicol and cycloheximide (SDA-CC). A parallel set of cultures incubated at 35°C showed bacterial growth on SDA but no growth on SDA-CC. Which of the following is the appropriate course of action?
Subculture the mold phase to moist BHI-blood media, incubate at 35°C.
Which of the following statements is true regarding the diagnosis of herpes simplex encephalitis caused by herpes simplex 1?
The virus is rarely recoverable from either spinal fluid or feces during herpes encephalitis.
Anaerobic infections differ from aerobic infections in which of the following?
They are usually polymicrobic.
Multifocal brain lesion in AIDS patients is commonly caused by:
Toxoplasma gondii
One of the enterotoxins produced by enterotoxigenic Escherichia coli in traveler's diarrhea is similar to a toxin produced by:
Vibrio cholerae
A two-week-old culture of a urine specimen produced a few colonies of acid-fast bacilli, which were 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?
Wait a few days and repeat the niacin test; report presumptive Mycobactenium tuberculosis if the test is more strongly positive
Which of the following gram-negative bacilli ferments carbohydrates?
Yersinia enterolitica
Proper collection of a sample for recovery of Enterobius vermicularis includes:
a swab from the perianal region before bathing or bowel movement
The optimal wound specimen for culture of anerobic organisims should be:
a syringe filled with pus, obtained before administrarion of antibiotics
Colds and other acute respiratory diseases are most often associated with:
adenovirus
The etiologic agent of botulism is:
an exotoxin producer
A penicillin-resistant Neisseria gonorrhoeae produces:
beta-lactamase
Streptococcus pneumoniae can be differentiated best from the viridans group of streptococci by:
bile solubility
Psittacosis is transmissible to man via contact with:
birds
The best medium for culture of Francisella tularensis is:
cystine blood agar
A first-morning sputum specimen is received for acid-fast culture. The specimen is centrifuged, and the sediment is inoculated on two Lowenstein-Jensen slants that are incubated at 35°C in 5%-lO% CO2. After I week, the slants show abundant growth over the entire surface. Stains reveal gram-negative bacilli. To avoid this problem:
decontaminate the specimen with NALC-sodium hydroxide mixture
In concentration methods for acid-fast bacilli, the sputum must be:
digested then centrifuged
The most rapid means of detecting herpes virus in clinical specimens is:
direct immunofluorescence
Rickettsiae infecting man multiply preferentially within which of the following cells?
endothelial
An aspirate of a deep wound was plated on blood agar plates aerobically and anaerobically. At 24 hours there was growth on both plates. This indicates that the organism is:
facultatively anaerobic
Which compound, detected by Lugol's iodine, is used in the nonimmunologic detection of Chlamydia trachomatis in cell culture?
glycogen
Which of the following groups of viruses are BEST diagnosed by serologic methods:
human immunodeficiency virus, Epstein-Barr virus, and hepatitis B
A sputum specimen from a patient with a known Kiebsiella pneumoniae infection is received in the laboratory for fungus culture. The proper procedure for handling this specimen is to:
include media that have cycloheximide and chloramphenicol added to inhibit bacterial organisms and saprophytic fungi
A urine specimen was submitted for isolation of cytomegalovirus. 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:
incubate the culture tubes for 2 to 3 weeks longer
Respiratory syncytial virus (RSV) is best isolated using a:
nasopharyngeal aspirate
The most sensitive substrate for the detection of B-lactamases is:
nitrocefin
Which one of the following results is typical of Campylobacterjejuni?
optimal growth at 42oC
Used needles from blood collection should be:
placed in a puncture-proof container
Safe handling and disposal of laboratory generated infectious wastes require:
separation of infectious and noninfectious wastes
Tests for beta-lactamase production in Haemophilus influenzae:
should be performed on all blood and CSF isolates
Anaerobic susceptibility tests are helpful in the management of patients with:
synovial infections
A control strain of Clostridium should be used in the GasPakTM anaerobe jar to ensure:
that anaerobic environment is achieved
The species of mycobacteria that will give a positive niacin test is Mycobacterium:
tuberculosis
The expected colony count in a suprapubic urine from a healthy individual is:
0 CFU/mL
Which of the following clean voided urine culture counts indicates the patient probably has a urinary tract infection?
103 CFU/mL
When a Brucella species is suspected in a blood culture, the bottle should be held for a minimum of:
21 days
Because ultraviolet light is used to decontaminate the work surface inside a biological safety cabinet, the lamp should be replaced when the intensity compared to the original output reading differs by:
30%
Recent evidence has shown that specimens to be inoculated for the recovery of acid-fast bacilli should be centrifuged at approximately:
3500g
Fluid from a cutaneous black lesion was submitted for routine bacteriological culture. After 18 hours of incubation at 35oC there was no growth on MacConkey agar, but 3+ growth on sheep blood agar. The colonies were nonhemolytic, 4 to 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-stained smear of a typical colony showed large, gram-positive, rectangular rods. The organism is most likely:
Bacillus anthracis
An anaerobic gram-negative bacillus isolated from a blood culture following bowel surgery grew smooth, white, nonhemolytic colonies. A Gram stain showed a pale, bipolar-staining rod with rounded ends. Bile stimulated growth of the organism and catalase was produced. The isolate was not inhibited by colistin, kanamycin, or vancomycin; indole was not produced. The most likely identification of this isolate is:
Bactemidesfragilis
The Epstein-Barr virus is associated with which of the following?
Burkitt's lymphoma
A beta-hemolytic gram-positive coccus was isolated from the cerebrospinal fluid of a 2old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disk. Which of the following should be perfoi for the identification of the organism?
CAMP test
A catheterized urine specimen from an 82-year-old woman with recurrent infections is submitted for culture. The Gram stain reveals: Many WBCs No epithelial cells Many gram-negative rods Many gram-positive cocci in chains The physician requests that sensitivities be performed on all pathogens isolated. In addition to the sheep blood agar and EMB plates routinely used for urine cultures, the technologist might also process a(n):
CNA agar plate
Which of the following statements concerning the germ tube test is true?
Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively.
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:
Chlamydia trachomatis
Which one of the following organisms could be used as the positive quality control test for lecithinase on egg yolk agar?
Clostridium peifringens
An anaerobic, spore-forming, nonmotile, gram-positive bacillus isolated from a deep wound of the leg is most probably:
Clostridium perfringens
A Gram stain from a swab of a hand wound reveals: Moderate gram-positive cocci in chains Moderate large gram-negative bacilli Select the appropriate media that will selectively isolate each organism.
Columbia CNA, MacConkey
A technician is asked to clean out the chemical reagent storeroom and discard any reagents not used in the past 5 years. How should the technician proceed?
Consult MSDS sheets for proper disposal.
An HIV-positive patient began to show signs of meningitis. Spinal fluid was collected and cultured for bacteria and fungus. A budding, encapsulated yeast was recovered. Which organism is consistent with this information?
Cryptococcus neoformans
An organism that demonstrates budding yeast cells with wide capsules in an India ink prepration of spinal fluid is probably:
Cryptococcus neoformans
Differentiation of Mycobacterium avium from Mycobacterium intracellulare can be accomplished by:
DNA probe
The system that optimizes recovery of fungi from blood is:
Dupont IsolatorTM
At the present time Clostridium difficile toxin can be detected by:
EIA
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 four nuclei and each nucleus has a large karyosome that appears as a refractive dot. These oval-shaped cysts are most likely:
Endolimax nana
Infection of the urinary tract is most frequently associated with:
Escherichia 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 enterotoxins?
Escherichia coli
Quality control of the spot indole test requires the use of ATCC cultures of:
Escherichia coli and Enterobacter cloacae
The IMViC reaction differentiates:
Escherichia coli from Enterobacter
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 dark-field examination. No organisms are seen in the specimen. Which medium should be inoculated in an attempt to isolate the suspected organism?
Fletcher's semisolid
Crust from a cauliflower-like lesion on the hand exhibited brown spherical bodies 6-12 pm in diameter when examined microscopically. After 3 weeks of incubation at room temperature, a slow-growing black mold grew on Sabouraud's dextrose agar. Microscopic examination revealed Cladosporium, Phialophora, and Acrotheca types of sporulation. The probable identification of this organism is:
Fonsecaea pedrosi
Gram stain examination of a CSF specimen indicates the presence of yeasy-like cells with gram-positive granular inclusions. Which of the following techniques should be used next to assist in the identification of this organism?
India ink
Which of the following is a true statement about pigment production by Mycrobacterium kansii?
It is a result of beta carotene formationand accumulation.
Sodium bicarbonate and sodium citrate are components of which of the following?
JEMBEC system
Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningitidis?
Lactose degradation
The best medium for culture of Myobacterium tuberculosis is:
Lowenstein-Jensen's
Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar base media?
Lowenstein-Jensen, Middlebrook 7H1 1, Lowenstein-Jensen (Gruft Modification)
A cell culture line commonly used for the recovery of Chiamydia trachomatis from clinical specimens is:
McCoy's
Culture of a strand of hair that fluoresced yellow-green when examined with a Wood's lamp produced a slow-growing, flat gray colony with a salmon-pink reverse. Microscopic examination demonstrated racquet hyphae, pectinate bodies, chiamydospores, and a few abortive or bizarre-shaped macroconidia. The most probable identification of this isolate is:
Microsporum 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?
Mycobacterium tuberculosis
Which one of the following species of Mycobacterium does NOT usually fluoresce on fluorochrome stain?
Mycobacteriumfortuitum
Which of the following reagents should be used as a mucolytic, alkaline reagent for digestion and decontamination of a sputum for mycobacterial culture?
N-acetyl-L-cystine and NaOH
Primary amebic-encephalitis may be caused by:
Naeglenia sp
Coagglutination is associated with:
Neisseria gonorrhoeae
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:
Nocardia asteroides
Organisms that can be easily identified to the species level from the ova in fecal specimens include:
Paragonimus westermani, Hymenolepis nana
Which of the following anaerobes is inhibited by sodium polyanethol sulfonate (SPS)?
Peptostreptococcus anaerobius
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-stained blood film revealed many intraerythrocytic parasites. Further history revealed frequent camping trips near Martha's Vineyard and Nantucket Island, but no travel outside the continental United States. This parasite could easily be confused with:
Plasmodium falciparum
The stock cultures needed for quality control testing of deamination activity are:
Proteus mirabilis/Escherichia coli
In the USA, the most common organism causing eumycetic mycetoma is:
Pseudallescheria boydii
A request is recieved in the laboratory for assitance in selecting the appropriate test(s) for detecting Lyme disease. Which of the following would be suggested?
The organisim is difficult to isolate, and antibody titers will provide the most help.
Patient specimens are being tested for Brucella antibody. Which course of action is most appropriate when the control serum displays a titer that is fourfold lower than expected?
The results should not be reported; the test should be repeated on the original specimen and a new control.
Which organism fails to grow on artificial media or in cell cultures?
Treponema pallidum
Which of the following is the most appropriate organisim and media combination?
Yersinia enterocolitica - cefsulodin-irgasan-novobiocin (CIN)
The diagnosis of Neisseria gonorrhoeae in females is best made from:
a cervical culture
Which of the two different antimicrobial agentsnlisted below are commaonly used and may result in synergistic action in the treatment of endocarditis caused by Enterococcus faecalis?
a penicillin derivative and an aminoglycoside
The procedure that ensures the most accurate results of oxacillin (methicillin) susceptibility testing against staphylococci is:
addition of 4% NaCl
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, inoculated on two Lowenstein-Jensen slants, and held for 8 weeks at 35°C in 5%-10% CO2. No growth occurs. The best explanation is that:
an improper specimen was submitted for culture
Gram stain of a deep wound showed many gram-positive spore-forming rods. 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 the culture should have been incubated:
anaerobically
When combined antimicrobial drugs are clearly less effective than the most active drug alone, the condition is described as:
antagonism
Penicillium can best be separated from Aspergillus by:
arrangement of the conidia on the conidiophore
The Gram stain procedure in the procedure manual calls for acetone-alcohol decolorization for 2 minutes. The best course of action for a newly employed technologist would be to:
ask the supervisor if this is indeed the timing to be followed
Which of the following is the most appropriate method for collecting a urine specimen from a patient with an indwelling catheter?
aspirate urine aseptically from the catheter tubing
A direct smear of a sputum specimen that demonstrated acid-fast bacilli would:
be reported and cultures done for isolation
The ONPG test allows organisms to be classified as a lactose fermenter by testing for which of the following?
beta-galactosidase
Haemophilus influenzae becomes resistant to ampicillin when the organism produces a(n):
beta-lactamase
Propionibacterium acnes is most often associated with:
blood culture contamination
A gram-negative rod 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?
boil the organism and retest with the antisera
An organism previously thought to be nonpathogenic, Moraxella (Branhamella) catarrhalis, is now known to be associated with infection and nosocomial transmission. Characteristic identification criteria include:
carbohydrates negative
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:
catalase production and coagulase test
The MOST common cause for failure of a GasPakTM anaerobic jar to establish an adequate environment for anaerobic incubation is:
catalysts that have become inactivated after repeated use
In the Kirby-Bauer disk diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic susceptibility?
cation content of media
The direct quellung reaction using specific antiserum is useful in the bacteriologic examination of which of the following specimens?
cerebrospinal fluid for Streptococcus pneumoniae
Media used to support growth of Legionella pneumophila should contain which of the following additives?
charcoal and yeast extract
Proper media for culture of a urethral discharge from a man include:
chocolate and modified Thayer-Martin agars
A reliable test for distinguishing pathogenic strains from nonpathogenic strains of staphylococci is:
coagulase
The most critical distinction between Staphylococcus aureus and other staphylococci is:
coagulase production
Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?
coagulation
The most reliable serologic test for the diagnosis of Q fever is the:
complement fixation test
An unusual number of Mycobacteria gordone have been isolated. This organism is reported as a "probable contaminant." The MOST likely source is:
contamination by water organisms
. In the disk diffusion method of determining antibiotic susceptibility, the size of the inhibition zone used to indicate susceptibility has been determined by:
correlating the zone size with minimum inhibitory concentrations
Which of the following procedures should be performed to confirm that an unknown mold is one of the pathogenic dimorphic fungi?
culture conversion to yeast form
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 from this specimen on buffered charcoal yeast extract (CYE) medium after 2 days of incubation. The best explanation is that the:
culture was not incubated long enough
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% CO2. The smears reveal acid-fast bacilli, and after 7 days no growth appears on the slants. The best explanation is:
cultures held for insufficient length of time
In agar disk susceptibility testing, as an antimicrobic agent diffuses away from the disk, the concentration gradient is:
decreased
A gram-negative rod that does not grow on MacConkey or sheep blood agars but grows well on chocolate agar has been isolated from sputum. Which of the following tests should be done next to identify the organism?
determination of X and V factor requirements
Which of the following is the most apprpriate specimen source and primary media battery?
endocervical - chocolate, Thayer-Martin
The streptococci most likely to have a high MIC (minimum inhibitory concentration) with penicillin are:
enterococci
What material should be used to prepare slides for direct smear examination for virus detection by special stains or FA technique?
epithelial cells from the base of the lesion
After proficiency in performing disk diffusion susceptibility tests is demonstrated, the frequency of quality control can be reduced from daily to:
every week
A liquid fecal specimen from a three-month-old infant is submitted for microbiologic examination. In addition to culture on routine media Salmonella and Shigella, this specimen routinely should be:
examined for the presence of Campylobacter sp
Routine quality control tests revealed that a batch of chocolate agar was able to support the growth of Haemophilus influenzae only as satellite colonies around Staphylococcus aureus. The most likely source of difficulty is:
excess heating in preparation of the medium
Photochromogens produce pigment when:
exposed to light for 1 hour
The most rapid and specific method for detection of Francisella tularensis is:
fluorescent antibody staining techniques on clinical specimens
The following results were obtained from a culture of unknown origin: Gram stain Gram-negative dipiococci Indophenol oxidase Positive Glucose Positive Maltose Negative Sucrose Negative The most likely source of the specimen would be the:
genitourinary tract
Antibiotics tested for isolates of Pseudomonas species include:
gentamicin
The preferred carbon source for mycobactena is:
glycerol
Which one of the following organisms does not require susceptibility testing when isolated from a clinically significant source?
group A streptococci
Beta-hemolytic streptococci that are bacitracin-resistant and CAMP-positive are:
group B
The organism most commonly associated with neonatal purulent meningitis is:
group B streptococci
A gamma-hemolytic Streptococcus, which blackens bile esculin but does not grow in 6.5% NaC1 broth, is most likely group:
group D nonenterococci
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:
growth of 6800 CFU/mL of a Streptococcus species, esculin hydrolysis and NaCl growth to follow
Infection rate is highest for laboratory professionals exposed to blood and body fluids containing:
hepatitis B
Encephalitis is most commonly associated with which of the following viruses?
herpes simplex
Definitive identification of Neisseria gonorrhoeae is made with the:
hydrolysis of carbohydrates
Which of the following would best differentiate Streptococcus agalactiae (Group B) from Streptococcus pyogenes (Group A)?
hydrolysis of sodium hippurate
Blood cultures from a case of suspected leptospiremia should be drawn:
in the first 7-10 days of infection
SPS is used as an anticoagulant for blood cultures because it:
inactivates neutrophils and components of serum complement
Which one of the following combinations of organisms would be appropriate as controls to test the functions listed?
indole--Escherichia coli and Proteus mirabilis
In processing clinical specimens and fungal isolates, laboratory workers may contract systemic fungal infections through:
inhalation
A skin abscess is submitted for mycobacterial culture on a patient who scraped his hand while cleaning his fish aquarium. The technologist should:
inoculate one set of media at 30C and one at 35C-37C
In order to isolate Campylobacter coli/jejuni, the fecal specimen should be:
inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42°C
Microorganisims resembling L-forms have been isolated from the blood of patients treated with antibiotics that:
interfere with cell wall synthesis
Which of the following indicates the presence of a viral infection in tissue smears or biopsies?
intranuclear inclusions
The cyst stage may be recovered from formed fecal specimens submitted for parasitic examination if the specimen:
is stored at refrigerator temperature
One advantage of the antimicrobial dilution tests is that:
it can detect varying degrees of organism sensitivity and resistance
All of the following are in vitro methods of determining synergism EXCEPT:
kill-curve using an MIC endpoint
Mycoplasmas differ from bacteria in that they:
lack cell walls
Which of the following is most often used to prepare a slide from a plate culture of a dermatophyte for microscopic observation?
lactophenol cotton blue
The function of N-acetyl-L-cysteine required in the NALC-NaOH reagent for acid-fast digestion-decontamination procedures is to:
liquify the mucus
The microscopic structures most useful in the identification of dermatophytes are:
macroconidia and microconidia
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 Mycobacterium:
marinum
Assuming the agent isolated from a patient's spinal fluid produces a positive oxidase test, the most likely diagnosis is:
meningococcal meningitis
The end point of the tube dilution test for antibiotic susceptibility is the:
minimal inhibitory concentration
The major features by which molds are routinely identified are:
mode of sporulation, morphology and arrangement of spores
The best procedure to differentiate Listeria monocytogenes from Corynebacterium species is:
motility at 25 oC
Biochemical reactions of an organism are consistent with Shigella. A suspension is tested in polyvalent antiserum without resulting agglutination. However, after 15 minutes of boiling, agglutination occurs in polyvalent and group D antisera. This indicates that the:
organism possesses capsular antigens
A urethral swab obtained from a man with a urethral exudate was plated directly on chocolate agar and modified Thayer-Martin (MTM) 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:
organism requires CO2 for growth
Haemophilus influenzae is most likely considered normal indigenous flora in the:
oropharynx
A 73-year-old man diagnosed as having pneumococcal meningititis is not responding to his penicillin therapy. Which of the following tests should be preformed on the isolate to best determine this organisim's susceptibility to penicillin agents?
oxacillin disk difussion
The agent used for processing specimens for mycobacterial culture contaminated with Pseudomonas is:
oxalic acid
Quality control results for disk diffusion susceptibility tests yield the aminoglycoside zones too small and the penicillin zones too large. This is probably due to the:
pH of Mueller-Hinton agar being too low
The genus of virus associated with anogenital warts, cervical dysplasia, and neoplasia is:
papillomavirus
An isolate on chocolate agar from a patient with epiglotyis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organisim is most likely Haemophilus:
parainfluenzae
An antibiotic that inhibits cell wall synthesis is:
penicillin
It has been recommended that cephalexin instead of penicillin be incorporated into BordetGengou agar because:
penicillin may inhibit some strains of Bordetella pertussis
Mycobacteria that produce pigment only after exposure to light are classified as:
photochromogens
An outbreak of Staphylococcus aureus has occurred in a hospital nursery. In order to establish the epidemiological source of the outbreak, it is helpful to do:
plasmid fingerprinting
Artifacts found in a stool specimen that can be confused with ova or cysts are:
pollen grains
The one characteristic by which an unknown Cryptococcus species can be identified as Cryptococcus neoformans is:
positive Niger seed agar test
A Gram stain of organisms on Loeffler agar showed pleomorphic gram-positive baci The organism should be subcultured to:
potassium tellurite
The characteristic MOST commonly associated with the presence of strict anaerobic bacteria and that can be taken as presumptive evidence of their presence in a clinical specimen is the:
presence of a foul, putrid odor from tissue specimens and cultures
Pseudomembranouscolitis caused by Clostridium difficile toxin is BEST confirmed by which of the laboratory findings?
presence of toxin in stool
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:
preserve the specimen in formalin until it can be examined
The main reason for the administration of two or more drugs for the treatment of pulmonary tuberculosis is to:
prevent the emergence of bacilli resistant to the action of either or both drugs
If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is:
production of pyocyanin pigment
The most important constituent of the tubercle bacilllus for the activity of the various tuberculins is the:
protein
With few exceptions, all members of the family Enterobacteriaceae show which of the following characteristics?
reduce nitrate to nitrite
A throat swab is submitted for anaerobic culture. This specimen should be:
rejected
Most of the automated microbiology equipment currently available has been designed to replace:
repetitive manual methods that are performed daily on a large number of specimens
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:
review the digestion and decontamination procedure
Which of the following viruses may be detected only by use of an electron microscope or EIA methods?
rotavirus
Enterococcal isolates from a patient with a case of endocarditis should be tested for routine susceptibility and:
screened for high-level aminoglycoside resistance
Skin scrapings obtained from the edge of a crusty wrist lesion were to contain thick-walled spherical yeast cells (8-15 um 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:
septate hyphae bearing round or pear-shaped small conidia attached to conidiophores of irregular lengths
Which of the following is most useful in establishing a diagnosis in the convalescence phase of a viral infection?
serological techniques
Material from a brain abscess is suspected to contain Bacteroides species. Isolation of this organism is best accomplished on:
sheep blood agar in anaerobic conditions
A gastric biopsy from a patient with severe gastritis and peptic ulcer is submitted to the laboratory with requests for Gram-stained touch preps and culture for Helicobacter (Campylobacter) pylori. The gram-negative rod is:
slender and curved
Which of the following is the best aid in the identifiaction of Epidermophyton floccosum macroconidia?
smooth walls, club-shaped
Which of the following is the best choice for decontaminating bench tops contaminated by the AIDS virus?
sodium hypochlorite bleach
Media for screening suspected cases of hemorrhagic E coli 0157:H7 must contain:
sorbitol
Production of beta-lactamase is inducible in which of the following?
staphylococus aureus
The porphyrin test was devised to detect strains of Haemophilus capable of:
synthesis of porphobilinogen
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?
the depth of the media was too thin
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:
the slide was inadequately decolorized with acetone/alcohol
When combination antibiotic therapy is used:
the synergistic effects of the drugs should be assessed
During the past month, Staphylococcus epidermidis has been isolated from blood cultures at two to three times the rate from the previous year. The most logical explanation for the increase in these isolates is that:
there has been a break in proper skin preparation before blood drawing
Differential skin testing for mycobacteriosis has diagnostic value in young children because:
they have not yet become sensitized to many mycobacteria
Vibrio parahaemolyticus can be isolated best from feces on:
thiosulfate citrate bile salts (TCBS) agar
Which of the following factors would make an organism appear to be more resistant on a disk diffusion susceptibility test?
too many organisms in the inoculum
When performing a Kovac's indole test, the substrate must contain:
tryptophane
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 l2B bottle and one Bactec 12B bottle with NAP. After reincubation, the uninoculated growth bottle shows an increase in growth index, while the bottle containing NAP shows no increase. The organism cultured from the sputum is Mycobactenium:
tuberculosis
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 which media?
urea broth
Chlamydial infections have been implicated in:
urethritis and conjunctivitis
The preferred specimen for laboratory diagnosis of acquired cytomegalovirus infection is:
urine
Which one of the following specimen requests is acceptable?
urine for culture of acid-fast bacilli
"Nutritionally deficient" streptococci are:
viridans streptococci
Acinetobacter lwoffi differs from Neissenia gonorrhoeae in that the former:
will grow on MacConkey and EMB media
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?
zones of larger diameter would result