BOC Microbiology real exam Questions with
Revised Answers| Verified 100% Correct
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
A. screened for high level aminoglycoside resistance
B. checked fo tolerance
C. assayed for serum antimicrobial activity
D. tested for beta-lactamase production - ✔✔Correct Answer: A
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
A. incubation temperature
B. duration of incubation
C. cation content of media
D. depth of agar - ✔✔Correct Answer: C
The procedure that assures the most accurate detection of mecA-mediated oxacillin
resistance in routine broth microdilution susceptibility testing against S. aureus is:
A. addition of 4% NaCl
B. incubation at 30 C
C. incubation for 48 hours
D. use of cefoxitin for testing - ✔✔Correct Answer: D
,When performing a stool culture, a colony type typical of an enteric pathogen is
subcultured on a blood agar plate. The resulting pure culture is screened with several
tests to obtain the following results:
-TSI: acid butt, alkaline slant, no gas, no H2S
-phenylalanine deaminase: negative
-motility: positive
-serological typing: Shigella flexneri (shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
A. report the organism as Shigella flexneri without further testing
B. verify reactivity of motility medium with positive and negative controls
C. verify reactivity of the TSI slants with positive and negative controls for H2S
production
D. verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Correct Answer: B
Susceptibility testing performed on quality control organism using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
A. the antibiotic disks were not stored with the proper desiccant
B. the depth of the media was too thick
C. the depth of the media was too thin
D. the antibiotic disks were not properly applied to the media - ✔✔Correct Answer: C
Three sets of blood cultures were obtained form an adult patient with fever and
suspected endocariditis. The aerobic bottle of one set had growth of Staphylococcus
epidermidis at 5 days of incubation. this indicates that:
A. there was low-grade bacteremia
,B. the organism is most likely a contaminant
C. the patient has a line infection
D. the blood culture bottles are defective - ✔✔Correct Answer: B
In order to isolate Camplobacter coli/jejuni, the fecal specimen should be:
A. inoculated onto selective plating media and incubated in reduced oxygen with added
CO2 at 42C
B. stored in tryptic soy broth before plating to ensure growth of the organism
C. inoculated onto selective plating media incubated at both 35C and at room
temperature
D. incubated at 35C for 2 hours in Cary-Blair media before inoculating onto selective
plating media - ✔✔Correct Answer: A
An expectorated sputum is sent to the laboratory for culture from a patient with
respiratory distress. The Gram stain of the specimen shows many squamous epithelial
cells (>25/lpf) and rare neutrophils. The microscopic appearance of the organisms
present include:
-moderate gram-positive cocci in chains and diplococci
-moderate gram-negative diplococci
-moderate palisading gram-positive bacilli all in moderate amounts
This Gram stain is most indicative of:
A. a pneumococcal pneumonia
B. an anaerobic infection
C. an Haemophilus pneumonia
D. oropharyngeal flora - ✔✔Correct Answer: D
Which type of microscope would be most useful in examining viruses and the structure
of microbial cells?
, A. electron
B. phase-contrast
C. dark-field
D. bright-field - ✔✔Correct Answer: A
After satisfactory performance of daily disk diffusion susceptibility quality control is
documented, the frequency of quality control can be reduced to:
A. twice a week
B. every week
C. every other week
D. every month - ✔✔Correct Answer: B
In disk diffusion susceptibility testing, as an antimicrocial agent diffuses away from the
disk, the concentration of antibiotic is:
A. increased
B. decreased
C. unchanged
D. inoculum dependent - ✔✔Correct Answer: B
The most common cause for failure of GasPak anaerobic jar to establish an adequate
environment for anaerobic incubation is:
A. the failure of the oxidation-reduction potential indicator system due to deterioration
of methylene blue
B. the failure of the packet to generate adequate H2 and/or CO2
C. condensation of water on the inner surface of the jar
D. catalysts that have become inactivated after repeated use - ✔✔Correct Answer: D
Revised Answers| Verified 100% Correct
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
A. screened for high level aminoglycoside resistance
B. checked fo tolerance
C. assayed for serum antimicrobial activity
D. tested for beta-lactamase production - ✔✔Correct Answer: A
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
A. incubation temperature
B. duration of incubation
C. cation content of media
D. depth of agar - ✔✔Correct Answer: C
The procedure that assures the most accurate detection of mecA-mediated oxacillin
resistance in routine broth microdilution susceptibility testing against S. aureus is:
A. addition of 4% NaCl
B. incubation at 30 C
C. incubation for 48 hours
D. use of cefoxitin for testing - ✔✔Correct Answer: D
,When performing a stool culture, a colony type typical of an enteric pathogen is
subcultured on a blood agar plate. The resulting pure culture is screened with several
tests to obtain the following results:
-TSI: acid butt, alkaline slant, no gas, no H2S
-phenylalanine deaminase: negative
-motility: positive
-serological typing: Shigella flexneri (shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
A. report the organism as Shigella flexneri without further testing
B. verify reactivity of motility medium with positive and negative controls
C. verify reactivity of the TSI slants with positive and negative controls for H2S
production
D. verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Correct Answer: B
Susceptibility testing performed on quality control organism using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
A. the antibiotic disks were not stored with the proper desiccant
B. the depth of the media was too thick
C. the depth of the media was too thin
D. the antibiotic disks were not properly applied to the media - ✔✔Correct Answer: C
Three sets of blood cultures were obtained form an adult patient with fever and
suspected endocariditis. The aerobic bottle of one set had growth of Staphylococcus
epidermidis at 5 days of incubation. this indicates that:
A. there was low-grade bacteremia
,B. the organism is most likely a contaminant
C. the patient has a line infection
D. the blood culture bottles are defective - ✔✔Correct Answer: B
In order to isolate Camplobacter coli/jejuni, the fecal specimen should be:
A. inoculated onto selective plating media and incubated in reduced oxygen with added
CO2 at 42C
B. stored in tryptic soy broth before plating to ensure growth of the organism
C. inoculated onto selective plating media incubated at both 35C and at room
temperature
D. incubated at 35C for 2 hours in Cary-Blair media before inoculating onto selective
plating media - ✔✔Correct Answer: A
An expectorated sputum is sent to the laboratory for culture from a patient with
respiratory distress. The Gram stain of the specimen shows many squamous epithelial
cells (>25/lpf) and rare neutrophils. The microscopic appearance of the organisms
present include:
-moderate gram-positive cocci in chains and diplococci
-moderate gram-negative diplococci
-moderate palisading gram-positive bacilli all in moderate amounts
This Gram stain is most indicative of:
A. a pneumococcal pneumonia
B. an anaerobic infection
C. an Haemophilus pneumonia
D. oropharyngeal flora - ✔✔Correct Answer: D
Which type of microscope would be most useful in examining viruses and the structure
of microbial cells?
, A. electron
B. phase-contrast
C. dark-field
D. bright-field - ✔✔Correct Answer: A
After satisfactory performance of daily disk diffusion susceptibility quality control is
documented, the frequency of quality control can be reduced to:
A. twice a week
B. every week
C. every other week
D. every month - ✔✔Correct Answer: B
In disk diffusion susceptibility testing, as an antimicrocial agent diffuses away from the
disk, the concentration of antibiotic is:
A. increased
B. decreased
C. unchanged
D. inoculum dependent - ✔✔Correct Answer: B
The most common cause for failure of GasPak anaerobic jar to establish an adequate
environment for anaerobic incubation is:
A. the failure of the oxidation-reduction potential indicator system due to deterioration
of methylene blue
B. the failure of the packet to generate adequate H2 and/or CO2
C. condensation of water on the inner surface of the jar
D. catalysts that have become inactivated after repeated use - ✔✔Correct Answer: D
