Harr & Elsevier Micro ERRORS

Chocolate agar and MTM agar are used for the recovery of:

A. Haemophilus spp. and Neisseria spp., respectively

B. Haemophilus spp. and N. gonorrhoeae, respectively

C. Neisseria spp. and Streptococcus spp., respectively

D. Streptococcus spp. and Staphylococcus spp., respectively

B. Haemophilus spp. and N. gonorrhoeae, respectively.

Xylose lysine deoxycholate (XLD) agar is a highly selective medium used for the recovery of which bacteria?

A. Staphylococcus spp. from normal flora

B. Yersinia spp. that do not grow on Hektoen agar

C. Enterobacteriaceae from gastrointestinal specimens

D. Streptococcus spp. from stool cultures

C. Enterobacteriaceae from gastrointestinal specimens

Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed, the specimen should be:

A. Refrigerated at 4°C to 6°C

B. Frozen at -20°C

C. Stored at room temperature for no longer than 24 hours

D. Incubated at 37°C and cultured as soon as possible

D. Incubated at 37°C and cultured as soon as possible

A suspected case of plague requires which of the following procedures to confirm Yersinia pestis?

A. Collection of multiple sets of blood culture specimens

B. Incubation of blood cultures at both 28°C and 35°C

C. Culture aspirates from bubos to MacConkey agar at room temperature

D. All of these options

D. All of these options

SITUATION: Several attendees of a medical conference in the Gulf coast area became ill after frequenting a seafood restaurant. A presumptive identification of V. cholerae was made after stool specimens from several subjects grew clear colonies on MacConkey agar and yellow colonies on TCBS agar. Which key tests would help eliminate Aeromonas and Plesiomonas spp.?

A. Mannitol fermentation, Na+ requirement

B. Oxidase, motility

C. Oxidase, nitrate

D. Hemolysis on blood agar, catalase

A. Mannitol fermentation, Na+ requirement

Deoxycholate agar (DCA) is useful for the isolation of:

A. Enterobacteriaceae

B. Enterococcus spp.

C. Staphylococcus spp.

D. Neisseria spp.

A. Enterobacteriaceae

A positive Simmons citrate test is seen as a:

A. Blue color in the medium after 24 hours of incubation at 35°C

B. Red color in the medium after 18 hours of incubation at 35°C

C. Yellow color in the medium after 24 hours of incubation at 35°C

D. Green color in the medium after 18 hours of incubation at 35°C

A. Blue color in the medium after 24 hours of incubation at 35°C

Care must be taken when identifying biochemical isolates of Shigella because

serological cross reactions occur with:

A. Escherichia coli

B. Salmonella spp.

C. Pseudomonas spp.

D. Proteus spp.

A. Escherichia coli

"Alkalescens-Dispar serotype"

Cronobacter sakazakii (formerly Enterobacter sakazakii) can best be differentiated from Enterobacter cloacae by which of the following characteristics?

A. Yellow pigmentation and negative sorbitol fermentation

B. Pink pigmentation and positive arginine dihydrolase

C. Yellow pigmentation and positive urease

D. H2S production on TSI

A. Yellow pigmentation and negative sorbitol fermentation

Which of the following organisms, found in normal fecal flora, may be mistaken biochemically for the genus Yersinia?

A. Klebsiella spp.

B. Proteus spp.

C. Escherichia coli

D. Enterobacter spp.

B. Proteus spp.

Proteus spp. are urease positive as are approximately 70% of Y. enterocolitica

isolates. Both organisms are lactose negative and motile. However, Yersinia is motile

at 22°C and not at 35°C (demonstrated by using motility media).

Which agar that is used for routine stool cultures is the medium of choice for the isolation of Yersinia strains from stool specimens?

A. Salmonella-Shigella agar

B. Hektoen enteric agar

C. MacConkey agar

D. CNA agar

C. MacConkey agar

"ROUTINE"

Which organism is sometimes mistaken for Salmonella and will agglutinate in

Salmonella polyvalent antiserum?

A. Citrobacter freundii strains

B. Proteus mirabilis strains

C. Shigella sonnei strains

D. Escherichia coli

A. Citrobacter freundii strains

Infections caused by Y. pestis are rare in the United States. Those cases that do occur are most frequently located in which region?

A. New Mexico, Arizona, and California

B. Alaska, Oregon, and Utah

C. North and South Carolina and Virginia

D. Ohio, Michigan, and Indiana

A. New Mexico, Arizona, and California

Which tests are most appropriate to differentiate between Pseudomonas aeruginosa and Pseudomonas putida?

A. Oxidase, motility, pyoverdin

B. Oxidase, motility, lactose

C. Oxidase, ONPG, DNase

D. Mannitol, nitrate reduction, growth at 42°C

D. Mannitol, nitrate reduction, growth at 42°C

P. putida:

Mannitol -

Nitrate red. -

Growth at 42C -

A specimen from a 15-year-old female burn patient was cultured after débridement, and the following results were obtained:

Oxidase = +

Lysine decarboxylase = Neg

Catalase = +

Motility = +

Ornithine decarboxylase = Neg

Glucose = + for oxidation (open tube)

Arginine dihydrolase = +

Maltose = Neg for oxidation (open tube)

Penicillin = Resistant

Aminoglycosides = Susceptible

Colistin (Polymixin B) = Susceptible

These results indicate which of the following organisms?

A. Acinetobacter spp.

B. Moraxella lacunata

C. Pseudomonas aeruginosa

D. Alcaligenes spp.

C. Pseudomonas aeruginosa

Chryseobacterium spp. and B. cepacia are easily differentiated by which test?

A. Motility

B. OF glucose

C. Oxidase

D. Cetrimide agar

A. Motility

Burkholderia cepacia (93%) are weakly oxidase positive and motile. Chryseobacterium spp. are oxidase positive but are nonmotile.

A nosocomial infection involving an 80-year-old female patient, recovering from pneumonia, produced many oxidase-negative colonies on MacConkey agar. Further testing results are:

Motility = +

Maltose = +

Resistant to most beta-lactams

Glucose = +

Resistant to most aminoglycosides

The most likely identification is:

A. Acinetobacter spp.

B. Stenotrophomonas maltophilia

C. Pseudomonas aeruginosa

D. Burkholderia gladioli

B. Stenotrophomonas maltophilia

S. maltophilia are oxidase negative, whereas all the other choices are oxidase positive

(B. gladioli are weakly oxidase positive).

Color that indicates a positive acetamide utilization test:

Blue

Positive control in Hippurate hydrolysis test:

S. agalactiae

Test most often used to separate the Micrococcaceae family from the Streptococcaeae family:

Catalase

Kingella kingae can best be differentiated from E. corrodens by using which medium?

A. Sheep blood agar

B. Chocolate agar

C. MacConkey agar

D. Xylose lysine deoxycholate agar

A. Sheep blood agar

(K. kingae strains produce a narrow zone of β-hemolysis on sheep blood agar similar to that of group B streptococci.)

Haemophilus species that require the V factor (NAD) are easily recovered on which primary agar plate?

A. Blood agar made with sheep RBCs

B. Blood agar made with horse RBCs

C. Chocolate agar

D. Xylose agar

C. Chocolate agar

(The V factor, NAD, must first be released from RBCs before it can be assimilated)

Which of the following plates should be used to identify H. haemolyticus and H. parahaemolyticus?

A. Sheep blood agar and chocolate agar

B. Horse blood agar and Mueller-Hinton agar with X and V strips

C. Brain-heart infusion (BHI) agar with sheep red cells added

D. Chocolate agar and Mueller-Hinton agar with X factor added

B. Horse blood agar and Mueller-Hinton agar with X and V strips

(Production of β-hemolysis is used to distinguish these two species)

A 7-year-old female became ill after eating a chicken sandwich from a fast-food restaurant. After 24 hours of gastroenteritis, a stool swab was obtained for culture, with normal fecal flora growing on Mac and XLD agars at 18 hours. Furthermore, growth was observed on Camp-BA at 48 hours (at both 42°C and 37°C incubation). Which test(s) differentiate C. jejuni subsp. doylei from C. jejuni subsp. jejuni because both grow at 37°C and 42°C?

A. Urease

B. Hippurate hydrolysis

C. Cephalothin and nalidixic acid antibiotic disks

D. Growth at 25°C

C. Cephalothin and nalidixic acid antibiotic disks

(C. jejuni subsp. jejuni are

resistant to cephalothin and susceptible to nalidixic acid. C. jejuni subsp. doylei are

susceptible to both disks.

42. A B. pertussis produces a virulence)

Micrococcus and Staphylococcus spp. are differentiated by which test(s)?

A. Fermentation of glucose (OF tube)

B. Catalase test

C. Gram stain

D. All of these options

A. Fermentation of glucose (OF tube)

(Micrococcus is non-fermentative)

Which of the following tests is used routinely to identify S. aureus?

A. Slide coagulase test

B. Tube coagulase test

C. Latex agglutination

D. All of these options

D. All of these options

Streptococcus species exhibit which of the following properties?

A. Aerobic, oxidase positive, and catalase positive

B. Facultative anaerobic, oxidase negative, catalase negative

C. Facultative anaerobic, β-hemolytic, catalase positive

D. May be α-, β-, or γ-hemolytic, catalase positive

B. Facultative anaerobic, oxidase negative, catalase negative

β-Hemolytic streptococci, not of group A or B, usually exhibit which of the following reactions?

A. Susceptible; Resistant

B. Resistant; Resistant

C. Resistant; Susceptible

D. Susceptible or resistant; Susceptible

D. Susceptible or resistant; Susceptible

A false-positive CAMP test result for the presumptive identification of group B

streptococci may occur if the plate is incubated in a(n):

A. Candle jar or CO2 incubator

B. Ambient air incubator

C. 35°C incubator

D. 37°C incubator

A. Candle jar or CO2 incubator

In addition to E. faecalis, which other streptococci will grow in 6.5% salt broth?

A. Group A streptococci

B. Group B streptococci

C. Streptococcus pneumoniae

D. Streptococcus bovis

B. Group B streptococci

The PYR hydrolysis test is a presumptive test for which group of β-hemolytic

streptococci?

A. Group A and Enterococcus

B. Group A and B β-hemolytic streptococci

C. Non-group A or non-group B β-hemolytic streptococci

D. Streptococcus pneumoniae and Streptococcus bovis

A. Group A and Enterococcus

Variation in colony types seen with fresh isolates of N. gonorrhoeae and sometimes with N. meningitidis are the result of:

A. Multiple nutritional requirements

B. Pili on the cell surface

C. Use of a transparent medium

D. All of these options

D. All of these options

Gram-negative diplococci recovered from an MTM plate and giving a positive oxidase test result can be presumptively identified as:

A. Neisseria gonorrhoeae

B. Neisseria meningitidis

C. Neisseria lactamica

D. All of these options

D. All of these options

Nonpathogenic Moraxella spp. capable of growing on selective media for Neisseria can best be differentiated from pathogenic Neisseria spp. by which test?

A. Catalase test

B. 10-unit penicillin disk on blood agar

C. Oxidase test

D. Superoxol test

B. 10-unit penicillin disk on blood agar

Cystine tryptic digest (CTA) media used for identification of Neisseria spp. should be inoculated and cultured in:

A. A CO2 incubator at 35°C for 24 hours

B. A CO2 incubator at 42°C for up to 72 hours

C. A non-CO2 incubator at 35°C for up to 72 hours

D. An anaerobic incubator at 35°C for up to 72 hours

C. A non-CO2 incubator at 35°C for up to 72 hours

(CTA carbohydrates must be placed in an ambient air incubator because a high CO2 concentration may reduce the pH, causing a false positive (acid) result.)

An oxacillin-disk screen test is used to detect S. pneumoniae resistance to penicillin. Using Mueller-Hinton agar with 5% sheep blood and a 1-μg oxacillin disk, what is the recommended inhibition zone size for penicillin susceptibility?

A. 5 mm or greater

B. 10 mm or greater

C. 15 mm or greater

D. 20 mm or greater

D. 20 mm or greater

A wound specimen was obtained from an older patient with diabetes and identified as being positive for vancomycin-resistant S. aureus (VRSA). The method used to determine VRSA was the standard microdilution technique. To be considered VSRA positive, which MIC must have been reported?

A. MIC 16μg/mL or greater

B. MIC of 8 to 16 μg/mL

C. MIC of 4 to 8 μg/mL

D. MIC 8 μg/mL or greater

A. MIC 16μg/mL or greater

A presumptive diagnosis of Gardnerella vaginalis can be made using which of the following findings?

A. Oxidase and catalase tests

B. Pleomorphic bacilli heavily colonized on vaginal epithelium

C. Hippurate hydrolysis test

D. All of these options

D. All of these options

(β-Hemolysis on BAP = +

Oxidase = Neg

Catalase = Neg

Hippurate hydrolysis = +)

Which is the test of choice for the confirmation of Chlamydia trachomatis infection in urine?

A. Enzyme immunoassay antigen testing

B. PCR molecular testing

C. Culture using McCoy and Hela cells

D. Microimmunofluorescence (MIF) test

B. PCR molecular testing

(Confirmation)

Identify the following bacterium-specimen pairing that is mismatched (specimen not appropriate for isolation):

A. Chlamydia (Chlamydophila) psittaci-fecal swab

B. Chlamydia trachomatis-first voided urine

C. Chlamydia trachomatis-endocervical swab

D. Chlamydia pneumonia-throat swab or sputum

A. Chlamydia (Chlamydophila) psittaci-fecal swab

(Lung infection)

An asymptomatic 25-year-old female patient with persistent nongonococcal urethritis (NGC) and pelvic inflammatory disease (PID) was suspected of being infected with Mycoplasma genitalium. Which category of testing should not be utilized to establish a final identification?

A. Nucleic acid amplification test (NAAT)

B. Real time PCR

C. PCR

D. Culture

D. Culture

(Culture techniques are time consuming and difficult to use as a screening procedure.)

Which of the following most affects the oxidation-reduction potential (Eh, or redox potential) of media for anaerobic bacteria?

A. Oxygen

B. Nitrogen

C. pH

D. Glucose

C. pH

Which of the following is the medium of choice for the selective recovery of gram-negative anaerobes?

A. Kanamycin-vancomycin-anaerobe (KVA) agar

B. Phenylethyl alcohol (PEA) agar

C. Cycloserine cefoxitin fructose agar (CCFA)

D. THIO broth

A. Kanamycin-vancomycin-anaerobe (KVA) agar

Which of the following organisms will display lipase activity on egg yolk agar?

A. Clostridium botulinum

B. Clostridium sporogenes

C. Clostridium novyi

D. All of these options

D. All of these options

Which mechanism is responsible for botulism in infants caused by C. botulinum?

A. Ingestion of spores in food or liquid

B. Ingestion of preformed toxin in food

C. Virulence of the organism

D. Lipase activity of the organism

A. Ingestion of spores in food or liquid

Antimicrobial susceptibility testing of Bacteroides and Clostridium spp. anaerobes are done by which of the following methods?

A. Broth microdilution

B. Agar dilution

C. E-Test

D. All of the above

D. All of the above

A Mycobacterium species recovered from a patient with AIDS gave the following results:

Niacin = Neg

Tween 80 hydrolysis = Neg

Heat-stable catalase (68°C) = ±

Nonphotochromogen

T2H = +

Nitrate reduction = Neg

What is the most likely identification?

A. Mycobacterium gordonae

B. Mycobacterium bovis

C. Mycobacterium avium complex

D. Mycobacterium kansasii

C. Mycobacterium avium complex

(M. avium complex is the Mycobacterium species most often isolated from patients with AIDS. It is biochemically inert, which is a distinguishing factor for identification.)

A laboratory provides the following services for identification of mycobacteria: Acid-fast staining of clinical specimens Inoculation of cultures

Shipment of positive cultures to a reference laboratory for identification

According to the ATS's definition for levels of service this laboratory is:

A. Level I

B. Level II

C. Level III

D. Level IV

A. Level I

Which of the following rapid-growing Mycobacterium spp. would most likely grow on a MacConkey agar plate and on other routine bacteriologic media?

A. Mycobacterium chelonae

B. Mycobacterium fortuitum

C. Mycobacterium abscessus

D. All of the above

D. All of the above

Which temperature range is ideal for the recovery of M. marinum?

A. 24°C to 26°C

B. 30°C to 32°C

C. 42°C to 44°C

D. 44°C to 48°C

B. 30°C to 32°C

What report should be given for the results of the following AFB smear?

Number of AFB seen = 2 per 300 fields

(1,000× magnification)

A. 1+

B. 2+

C. 3+

D. Indeterminate; repeat with new specimen

D. Indeterminate; repeat with new specimen

An isolate produced a constriction that was interpreted as a positive germ tube, but C. albicans was ruled out when confirmatory tests were performed. Which of the following fungi is the most likely identification?

A. Candida tropicalis

B. Cryptococcus neoformans

C. Candida glabrata

D. Rhodotorula rubra

A. Candida tropicalis

An isolate from CSF growing on cornmeal agar produces the following structures:

Blastoconidia = + Pseudohyphae = Neg

Chlamydoconidia = Neg Arthroconidia = Neg

Which tests should be performed next?

A. Birdseed agar and urease

B. Germ tube and glucose

C. India ink and germ tube

D. All of these options

A. Birdseed agar and urease

(A yeast that is isolated from CSF and is producing blastospores is most likely to be C. neoformans, which is positive for urease and produces brown colonies on birdseed agar.)

Which of the following yeasts produces only blastoconidia on cornmeal Tween 80 agar?

A. Candida spp.

B. Trichosporon spp.

C. Geotrichum spp.

D. Cryptococcus spp.

D. Cryptococcus spp.

A germ tube-negative, pink yeast isolate was recovered from the respiratory secretions and urine of a patient with AIDS. Given the following results, what is the most likely identification?

CORNMEAL TWEEN 80 AGAR

Blastoconidia = +

Pseudohyphae = Neg

Arthroconidia = Neg

Urease = +

A. Candida albicans

B. Rhodotorula spp.

C. Cryptococcus spp.

D. Trichosporon spp.

B. Rhodotorula spp.

Terminal chlamydoconidia production is demonstrated by which Candida species?

A. Candida glabrata

B. Candida krusei

C. Candida albicans

D. Candida tropicalis

C. Candida albicans

Carbohydrate assimilation tests are used for the identification of yeast isolates by inoculating media:

A. Free of carbohydrates

B. Free of niger seed

C. Containing carbohydrates

D. Containing yeast extract

A. Free of carbohydrates

Yeast recovered from the urine of a catheterized patient receiving chemotherapy for cancer gave the following results:

CORNMEAL TWEEN 80 AGAR

Germ tube = +

Pseudohyphae = +

Terminal chlamydoconidia = +

Blastoconidia = +

Arthroconidia = Neg

What further testing is necessary?

A. Carbohydrate assimilation and urease

B. Urease and niger seed

C. Nitrate reductase and carbohydrate fermentation

D. No further testing is needed for identification

D. No further testing is needed for identification

(This isolate is C. albicans, which also produces some true hyphae along with pseudohyphae.)

The yeast form of which dimorphic fungus appears as oval or elongated cigar shapes?

A. Coccidioides immitis

B. Sporothrix schenckii

C. Histoplasma capsulatum

D. Blastomyces dermatitidis

B. Sporothrix schenckii

The mycelial form of H. capsulatum seen on agar resembles:

A. Sepedonium spp.

B. Penicillium spp.

C. Sporothrix spp.

D. Coccidioides spp.

A. Sepedonium spp.

(Sepedonium spp. are saprophytic molds that do not have a yeast phase and produce large spherical tuberculate macroconidia, similar to H. capsulatum.)

A rapidly growing hyaline mold began as a white colony but soon developed a black "pepper" effect on the agar surface. The older colony produced a black matte, making it resemble a dematiaceous mold. What is the most likely identification?

A. Penicillium notatum

B. Aspergillus niger

C. Paecilomyces spp.

D. Scopulariopsis spp.

B. Aspergillus niger

(A. niger is the only species listed producing black conidia, which causes a "pepper" effect as the colony grows.)

Material from a fungus-ball infection produced colonies with a green surface on Sabouraud agar in 5 days at 30°C. Microscopic examination showed club-shaped vesicles with sporulation only from the top half of the vesicle. This hyaline mold is most probably which Aspergillus spp.?

A. Aspergillus niger

B. Aspergillus fumigatus

C. Aspergillus flavus

D. Aspergillus terreus

B. Aspergillus fumigatus

(It is characterized by sporulation only from the upper half or two-thirds of the vesicle.)

A rapidly growing nonseptate mold produced colonies with a gray surface resembling cotton candy that covered the entire plate. Microscopic examination revealed sporangiophores arising between, not opposite, the rhizoids and producing pear-shaped sporangia. What is the most likely identification?

A. Lichtheimis (formerly Absidia) spp.

B. Penicillium spp.

C. Rhizopus spp.

D. Aspergillus spp.

A. Lichtheimis (formerly Absidia) spp.

A bone marrow sample obtained from an immunocompromised patient revealed small intracellular cells using a Wright stain preparation. Growth on Sabouraud-dextrose agar plates of a mold phase at 25°C and a yeast phase at 37°C designates the organism as dimorphic. The mold phase produced thick, spherical tuberculated macroconidia. What is the most likely identification?

A. Histoplasma capsulatum

B. Sepedonium spp.

C. Sporothrix schenckii

D. Coccidioides immitis

A. Histoplasma capsulatum

(Thermally dimorphic H. capsulatum produce microconidia and hyphal fragments at 37°C (yeast phase), whereas at 25°C (mold phase), the organism displays large, thick-walled, round macroconidia with knobby or knoblike projections.)

Microscopically, Scopulariopsis spp. resemble Penicillium spp. Which of the following best differentiates the two?

A. Nonseptate hyphae and foot cells

B. Brush-like conidiophores and large echinulate conidia

C. No hyphae and no phialides

D. Growth at 45°C.

B. Brush-like conidiophores and large echinulate conidia

(Microscopically, Scopulariopsis spp. resemble Penicillium spp. except for the following: Scopulariopsis spp. produce annellophores with flask-shaped annelides bearing large lemon-shaped, rough-walled conidia in chains; Penicillium spp. display brush-like conidiophores producing metulae with flask-shaped phialides, resulting in chains of small, smooth-walled conidia.)

A fast-growing (2-5 days) culture of fluffy white to blue-green colonies from a

respiratory specimen obtained from an immunocompromised ICU patient showed septate hyphae with many conidiophores. The tips of the conidiophores expand into large dome-shaped vesicles with bottle-shaped phialides covering the upper half or two-thirds of its surface. Long chains of small conidia form a columnar mass on the surface. At the base of the conidiophore, a "foot cell" is seen attaching the conidiophore to the

septate hyphae. The most likely organism is?

A. Penicillium spp.

B. Scopulariopsis spp.

C. Aspergillus fumigatus

D. Paecilomyces spp.

C. Aspergillus fumigatus

A "foot cell" is characteristic of Aspergillus fumigatus.

Which virus is the most common etiological agent of viral respiratory diseases in infants and children?

A. Respiratory syncytial virus (RSV)

B. Measles virus

C. Coxsackie A virus

D. Coxsackie B virus

A. Respiratory syncytial virus (RSV)

(RSV is the cause of croup, bronchitis, bronchiolitis, and interstitial pneumonia. Hospitalized children age less than 1 year are the most susceptible group.)

The most common viral syndrome of pericarditis, myocarditis, and pleurodynia (pain upon breathing) is caused by:

A. Herpes simplex virus (HSV)

B. Respiratory syncytial virus

C. Epstein-Barr virus (EBV)

D. Coxsackie B virus

D. Coxsackie B virus

(Coxsackie A virus, Coxsackie B virus, and the echoviruses are most commonly implicated in myocarditis and other syndromes, including acute cerebellar ataxia and hepatitis.)

Which technique is used for the confirmation of infection with HIV-1 and HIV-2?

A. Western blot (immunoblot) assay

B. ELISA

C. FDA-approved NAT

D. p24 Antigen testing

C. FDA-approved NAT

A 65-year-old woman was admitted to the hospital with acute respiratory distress, fever, myalgia, and headache. Influenza A or B was suspected after ruling out bacterial pneumonia. Which of the following methods could be used to confirm influenza infection?

A. EIA

B. RT-PCR

C. Direct examination of nasal epithelium for virus using fluorescent antibody stain

D. All of these options

D. All of these options

A 60-year-old male gardener from New York State was hospitalized with flulike symptoms and was eventually diagnosed with encephalitis. While working in his garden, he had noticed several dead birds around his bird feeder. The region is known for heavy mosquito infestation. What is the most likely cause of his illness?

A. West Nile virus

B. Epstein-Barr virus

C. Parvovirus

D. Hantavirus

A. West Nile virus

(Transmission of West Nile virus is from mosquito to bird.)

A 30-year-old male patient, who was a contractor and building inspector in the southwestern United States, complained of difficulty breathing and was admitted to the hospital with severe respiratory disease. The physician noted a high fever and cough. Two days earlier, the patient had inspected an old abandoned warehouse that was infested by rodents. The patient was given intravenous antibiotics, but 2 days into therapy, the pneumonia worsened, leading to pulmonary edema. Which organism should be suspected of causing his illness?

A. Hantavirus

B. Rotavirus

C. West Nile virus

D. Norovirus (formerly Norwalk-like virus)

A. Hantavirus

(Hantavirus is transmitted by a rodent host, the deer mouse, was originally endemic in the southwest United States, but currently has been discovered throughout the country. The name of the hantavirus responsible for outbreaks in the southwest is the Sin Nombre virus.)

A 25-year-old pregnant female with genital lesions delivered a premature newborn with complications. The baby tested negative for bacterial infection (cultures of blood and urine). Antigen testing of the baby's urine proved negative for group B streptococci and S. pneumoniae. The mother tested negative for bacterial sexually transmitted diseases (STDs) and for group B streptococci. The baby was treated with acyclovir but failed to survive. What was the most likely cause of death?

A. CMV

B. HIV

C. RSV

D. HSV

D. HSV

(HSV-2 infections produce genital lesions. Infants born prematurely with disseminated infection of HSV-2 from HSV-positive mothers have a mortality rate of 50% to 60%.)

The organs of a 65-year-old male were donated soon after a fatal auto accident. Three recipients of his corneas and kidneys died within weeks after receiving his organs. Which of the following viruses most likely caused the death of these recipients?

A. Human immunodeficiency virus

B. Rabies

C. Norovirus (Norwalk-like virus)

D. Rotavirus

B. Rabies

(Transmission of rabies (rhabdovirus) occurs primarily from the bite of a rabid animal, but in 20% of human rabies cases, there is no known exposure to rabid animals. Donor tissues are not routinely tested for rabies.)

Parasitic organisms that may be transmitted sexually do not include:

A. Entamoeba gingivalis

B. Dientamoeba fragilis

C. Trichomonas vaginalis

D. Diphyllobothrium latum

D. Diphyllobothrium latum

(Ingestion of fish infected with plerocercoid larva)

The following organisms are linked with specific, relevant information. The incorrect combination is:

A. Strongyloides stercoralis—internal autoinfection

B. Echinococcus granulosus—hydatid examination

C. Toxoplasma gondii—serology

D. Balantidium coli—common in the United States

D. Balantidium coli—common in the United States

Two helminth eggs that may resemble one another are:

A. Diphyllobothrium latum and Paragonimus westermani

B. Opisthorchis sinensis and Fasciolopsis buski

C. Taenia saginata and Hymenolepis nana

D. Ascaris lumbricoides and Trichostrongylus

A. Diphyllobothrium latum and Paragonimus westermani

(Both D. latum and P. westermani eggs are operculated and approximately the same size.)

Humans acquire infections with Diphyllobothrium latum adult worms by:

A. Ingestion of freshwater crabs

B. Skin penetration of cercariae

C. Ingestion of water chestnuts

D. Ingestion of raw freshwater fish

D. Ingestion of raw freshwater fish

Organisms (and infections) that under normal conditions cannot be transmitted in the laboratory are:

A. Cryptosporidium—cryptosporidiosis

B. Taenia solium—cysticercosis

C. Ascaris lumbricoides—ascariasis

D. Enterobius vermicularis—pinworm infections

C. Ascaris lumbricoides—ascariasis

(A. lumbricoides eggs require a period of development in the soil before they are infective for humans.)

Eye infections with Acanthamoeba spp. have most commonly been traced to:

A. Use of soft contact lenses

B. Use of hard contact lenses

C. Use of contaminated lens care solutions

D. Failure to remove lenses while swimming

C. Use of contaminated lens care solutions

(The majority of eye infections with Acanthamoeba spp. have resulted from the use of contaminated eye care solutions, primarily the use of homemade saline.)

Protozoan cysts were seen in a concentration sediment and tentatively identified as Entamoeba coli. However, the organisms were barely visible on the permanent stained

smear because:

A. The organisms were actually not present in the concentration sediment

B. There were too few cysts to allow identification on the stained smear

C. Entamoeba coli cysts were present but poorly fixed due to the thick cyst wall

D. The concentrate and permanent stained smear were not from the same patient

C. Entamoeba coli cysts were present but poorly fixed due to the thick cyst wall

(As E. coli cysts mature, the cyst wall becomes more impenetrable to fixatives.)

A 60-year-old Brazilian patient with cardiac irregularities and congestive heart failure suddenly dies. Examination of the myocardium revealed numerous amastigotes, an indication that the cause of death was most likely:

A. Leishmaniasis with Leishmania donovani

B. Leishmaniasis with Leishmania braziliense

C. Trypanosomiasis with Trypanosoma gambiense

D. Trypanosomiasis with Trypanosoma cruzi

D. Trypanosomiasis with Trypanosoma cruzi

(T. cruzi, the cause of Chagas disease, exists in two forms within humans, the trypomastigote in the blood and the amastigote in the striated muscle (usually cardiac muscle and intestinal tract muscle).

In an outbreak of diarrheal disease traced to a municipal water supply, the most likely causative agent is:

A. Cryptosporidium spp.

B. Cystoisospora belli

C. Entamoeba histolytica

D. Dientamoeba fragilis

A. Cryptosporidium spp.

(Cryptosporidium can be transmitted through contaminated municipal water sources. Such outbreaks have been well documented.)

Ingestion of which of the following eggs will result in infection?

A. Strongyloides stercoralis

B. Schistosoma japonicum

C. Toxocara canis

D. Opisthorchis sinensis

C. Toxocara canis

(The eggs of T. canis are infectious for humans and cause visceral and ocular larva migrans.)

Microsporidia have been identified as causing severe diarrhea, disseminated disease in other body sites, and ocular infections. Routes of infection have been identified as:

A. Ingestion

B. Inhalation

C. Direct contamination from the environment

D. Ingestion, inhalation, and direct contamination from the environment

D. Ingestion, inhalation, and direct contamination from the environment

Confirmation of an infection with microsporidia can be achieved by seeing:

A. The oocyst wall

B. Sporozoites within the oocyst

C. Evidence of the polar tubule

D. Organisms stained with modified acid-fast stains

C. Evidence of the polar tubule

(Evidence of the cross/diagonal line polar tubules provides confirmation for

microsporidial spores in the clinical specimen; the stain of choice is the modified trichrome stain - Ryan/blue or Weber/green)

Although the pathogenicity of Blastocystis spp. remains controversial, newer information suggests that:

A. Most organisms are misdiagnosed as artifacts

B. Approximately 10 subtypes/strains are included in the name, some of which are pathogenic and some are nonpathogenic

C. The immune status of the host is solely responsible for symptomatic infections

D. The number of organisms present determines pathogenicity

B. Approximately 10 subtypes/strains are included in the name, some of which are pathogenic and some are nonpathogenic

*Correct reporting of this infection should be Blastocystis spp.; numbers should also be reported (rare, few, moderate, many, packed).

Potential problems using EDTA anticoagulant and holding the blood too long prior to preparation of thick and thin blood films include:

A. Changes in parasite morphology, loss of organisms within several hours, and poor staining

B. Loss of Schüffner dots, poor adherence of the blood to the glass slide, and parasites beginning the vector cycle within the tube of blood

C. None of the above

D. All of the above

D. All of the above

Which group of tests, along with colonial morphology on primary media, aids most in the rapid identification of Enterobacteriaceae?

A. MR and VP, urease, and blood agar plate

B. Phenylalanine deaminase, urease, and CDC agar plate

C. Bacitracin, β-lactamase, and MacConkey agar plate

D. Indole, oxidase, MacConkey, and blood agar plates

D. Indole, oxidase, MacConkey, and blood agar plates

The drugs of choice for treatment of infections with Enterobacteriaceae are:

A. Aminoglycosides, sulfamethoxazole-trimethoprim, third generation cephalosporins

B. Ampicillin and nalidixic acid

C. Streptomycin and isoniazid (isonicotinylhydrazide [INH])

D. Chloramphenicol, ampicillin, and colistin

A. Aminoglycosides, sulfamethoxazole-trimethoprim, third generation cephalosporins

Examination of a modified acid-fast-stained fecal smear reveals round structures measuring approximately 8 to 10 μm, some of which are stained and some of which are not. They do not appear to show any internal morphology. The patient is symptomatic with diarrhea, and the cause may be:

A. Blastocystis spp.

B. Polymorphonuclear leukocytes

C. Cyclospora cayetanensis

D. Large yeast cells

C. Cyclospora cayetanensis

A nursing student working in the emergency department accidentally suffered a needlestick after removing an intravenous set from a suspected drug user. The best course of action, after reporting the incident to her supervisor, is to:

A. Test the student for HIV virus if flulike symptoms develop in 2 to 4 weeks

B. Immediately test the patient and the student for HIV by using an EIA or ELISA test

C. Perform a Western blot assay on the student's serum

D. Draw blood from the student only and freeze it for further testing

B. Immediately test the patient and the student for HIV by using an EIA or ELISA test

A dehydrated 25-year-old male patient was admitted to the hospital with symptoms similar to those of chronic fatigue syndrome. Serological testing proved negative for recent streptococcal infection, EBV, and hepatitis. Which of the following viral serological tests should help with a possible diagnosis?

A. CMV

B. Echovirus

C. RSV

D. Measles virus

A. CMV

In breakpoint antimicrobial drug testing, interpretation of susceptible (S), intermediate (I), and resistant (R) refers to testing antibiotics by using:

A. The amount needed to cause bacteriostasis

B. Only the specific concentrations necessary to report S, I, or R

C. An MIC of 64 μg/mL

D. A dilution of drug that is one tube less than the toxic level

B. Only the specific concentrations necessary to report S, I, or R

A 65-year-old female outpatient was requested by her physician to submit a 24-hour urine specimen for protein and creatinine tests. He also requested testing for mycobacteria in the urine. Should the microbiology laboratory accept this 24-hour specimen for culture?

A. Yes, if the specimen is kept on ice

B. Yes, if the specimen is for aerobic culture only

C. No, the specimen must be kept at room temperature

D. No, the specimen is unsuitable for the recovery of mycobacteria

D. No, the specimen is unsuitable for the recovery of mycobacteria

(a first morning specimen is best

for the recovery of mycobacteria in the urine.)

SITUATION: A patient tested positive for HIV-1 infection with use of a RT-PCR method. However, 1 week later, a second blood sample was collected and sent to a reference laboratory, which performed a confirmatory Western blot test. The Western blot test was negative. What best explains these results?

A. The samples for RT-PCR and Western blot were not from the same patient

B. RT-PCR is more sensitive for early detection

C. The RT-PCR result was falsely positive

D. The RT-PCR test detected HIV-2 and the Western blot is specific for HIV-1

B. RT-PCR is more sensitive for early detection

A 20-year-old female college student complained of a sore throat and extreme fatigue. The physician noted lymphadenopathy and ordered a rapid test for infectious mononucleosis antibodies that was negative. Bacterial cultures were negative, as were serological tests for influenza A and B, HIV-1, CMV, hepatitis B, and antistreptolysin O. What would be the next line of viral testing to establish a diagnosis?

A. Herpes simplex

B. Rubella

C. Epstein-Barr

D. West Nile

C. Epstein-Barr

Which dematiaceous mold forms flask-shaped phialides, each with a flask-shaped collarette?

A. Phialophora spp.

B. Exophiala spp.

C. Wangiella spp.

D. All of these options

A. Phialophora spp.

A blood agar plate inoculated with sputum from a patient with diabetes mellitus grew very few bacterial flora and a predominance of yeast. Given the following results, what is the most likely identification of the yeast isolate?

CORNMEAL TWEEN 80 AGAR

Germ tube = Neg

Arthroconidia = Neg

Pseudohyphae = +

Blastoconidia = + (arranged along pseudohyphae)

Chlamydoconidia = Neg

A. Candida tropicalis

B. Candida kefyr (pseudotropicalis)

C. Trichosporon cutaneum

D. Geotrichum candidum

A. Candida tropicalis

The urease test, niger seed agar test, and the germ tube test are all used for the presumptive identification of:

A. Rhodotorula rubra

B. Cryptococcus neoformans

C. Trichosporon cutaneum

D. Candida albicans

B. Cryptococcus neoformans