BOC Microbiology Exam Questions
and Answers Already Passed
Which species of Shigella is most commonly associated with diarrheal disease in the
united states? - Answer-S. sonnei
Which of the following tests best differentiates Shigella species from E. coli? - Answer-
Lactose, indole, ONPG, and motility (Shigella is negative for all)
Which genera of Enterobacteriaceae ae usually nonmotile at 36C? - Answer-Shigella,
Klebsiella, and Yersinia
Fever, abdominal cramping, watery stools, and fluid and elecrolyte loss preceded by
bloody stools 2-3 days before is characteristic of shigellosis, but may also result from
infection with: - Answer-Campylobacter spp.
Cold enrichment of feces (incubation at 4C) in phosphate-buffered saline prior to
subculture onto enteric media enhances the recovery of: - Answer-Yersinia
enterocolitica
Which group of tests, along with colonial morphology on primary media, aids most in the
rapid identification of the Enterobacteriaceae? - Answer-Indole, oxidase, MacConkey,
and Blood agar plates
A routine, complete stool culture procedure should include media for the isolation of E.
coli O157:H7 as well as: - Answer-Salmonella, Shigella, Yersinia, Campylobacter and
Staphylococcus aureus.
Which group of tests best identifies the Morganella and Proteus genera? - Answer-
Motility, urease, and phenylalanine deaminase
Which group of test best differentiates Enterobacter aerogenes from Edwardsiella
tarda? - Answer-Hydrogen sulfide(H2S) production, sucrose fermentation, indole, and
VP.
Enterobacter sakazakii can best be differentiated from Enterobacter cloacae by which of
the following characteristics? - Answer-Yellow pigmentation and negative sorbitol
fermentation.
, Members of the genus Cedecea are best differentiated from Serratia spp. by which test
result? - Answer-Negative DNase (negative in Cedecea spp.)
Which of the following organisms is often confused with the salmonella species
biochemically and on plated media? - Answer-Citrobacter freundii
A gram-negative rod is recovered from a catheterized urine sample from a nursing
home patient. The lactose-negative isolate tested positive for indole, urease, ornithine
decarboxylase and phenylalanine deaminase and negative for H2S. The most probable
identification is: - Answer-Morganella spp.
Which single test best separates Klebsiella oxytoca from K. pneumonia? - Answer-
Indole, where K. pneumonia is negative, and K. oxytoca is positive.
Which of the following organisms, found in normal fecal flora, may be mistaken
biochemically for the genus Yersinia? - Answer-Proteus spp.
Why might it be necessary for both pink (lactose-positive) and colorless (lactose-
negative) colonies from an initial stool culture on MacConkey agar to be subcultured
and tested further for possible pathogens? - Answer-Pathogenic E.coli can be lactose
positive or lactose negative.
Which agar that is used for routine stool cultures is the medium of choice for the
isolation of Yersinia strains from stool specimens? - Answer-MacConkey agar
Which organism is sometimes mistaken for Salmonella and will agglutinate in
Salmonella polyvalent antiserum? - Answer-C. freundii strains
A bloody stool cultured from a 26-year old woman after 3 days of severe diarrhea
showed the following results at 48 hours after being plated on the following media:
-MAC little normal flora with many non-lactose fermenting colonies
-Hektoen agar many blue-green colonies
-No growth on Campy and C. diff agar
-oxidase, indole , urease, motility and H2S negative from colonies on MAC. - Answer-
Shigella
Which of the following organisms are generally positive for Beta-galactosidase? -
Answer-E. coli
In the Kauffmann-White schema, the combined antigens used for serological
identifications of Salmonella spp. are: - Answer-O, Vi and H antigens
The drugs of choice for treatment of infections with Enterobacteriacea are: - Answer-
Aminoglycosides, trimethoprim-sulfamethoxazole, and third-generation cephalosporins.
and Answers Already Passed
Which species of Shigella is most commonly associated with diarrheal disease in the
united states? - Answer-S. sonnei
Which of the following tests best differentiates Shigella species from E. coli? - Answer-
Lactose, indole, ONPG, and motility (Shigella is negative for all)
Which genera of Enterobacteriaceae ae usually nonmotile at 36C? - Answer-Shigella,
Klebsiella, and Yersinia
Fever, abdominal cramping, watery stools, and fluid and elecrolyte loss preceded by
bloody stools 2-3 days before is characteristic of shigellosis, but may also result from
infection with: - Answer-Campylobacter spp.
Cold enrichment of feces (incubation at 4C) in phosphate-buffered saline prior to
subculture onto enteric media enhances the recovery of: - Answer-Yersinia
enterocolitica
Which group of tests, along with colonial morphology on primary media, aids most in the
rapid identification of the Enterobacteriaceae? - Answer-Indole, oxidase, MacConkey,
and Blood agar plates
A routine, complete stool culture procedure should include media for the isolation of E.
coli O157:H7 as well as: - Answer-Salmonella, Shigella, Yersinia, Campylobacter and
Staphylococcus aureus.
Which group of tests best identifies the Morganella and Proteus genera? - Answer-
Motility, urease, and phenylalanine deaminase
Which group of test best differentiates Enterobacter aerogenes from Edwardsiella
tarda? - Answer-Hydrogen sulfide(H2S) production, sucrose fermentation, indole, and
VP.
Enterobacter sakazakii can best be differentiated from Enterobacter cloacae by which of
the following characteristics? - Answer-Yellow pigmentation and negative sorbitol
fermentation.
, Members of the genus Cedecea are best differentiated from Serratia spp. by which test
result? - Answer-Negative DNase (negative in Cedecea spp.)
Which of the following organisms is often confused with the salmonella species
biochemically and on plated media? - Answer-Citrobacter freundii
A gram-negative rod is recovered from a catheterized urine sample from a nursing
home patient. The lactose-negative isolate tested positive for indole, urease, ornithine
decarboxylase and phenylalanine deaminase and negative for H2S. The most probable
identification is: - Answer-Morganella spp.
Which single test best separates Klebsiella oxytoca from K. pneumonia? - Answer-
Indole, where K. pneumonia is negative, and K. oxytoca is positive.
Which of the following organisms, found in normal fecal flora, may be mistaken
biochemically for the genus Yersinia? - Answer-Proteus spp.
Why might it be necessary for both pink (lactose-positive) and colorless (lactose-
negative) colonies from an initial stool culture on MacConkey agar to be subcultured
and tested further for possible pathogens? - Answer-Pathogenic E.coli can be lactose
positive or lactose negative.
Which agar that is used for routine stool cultures is the medium of choice for the
isolation of Yersinia strains from stool specimens? - Answer-MacConkey agar
Which organism is sometimes mistaken for Salmonella and will agglutinate in
Salmonella polyvalent antiserum? - Answer-C. freundii strains
A bloody stool cultured from a 26-year old woman after 3 days of severe diarrhea
showed the following results at 48 hours after being plated on the following media:
-MAC little normal flora with many non-lactose fermenting colonies
-Hektoen agar many blue-green colonies
-No growth on Campy and C. diff agar
-oxidase, indole , urease, motility and H2S negative from colonies on MAC. - Answer-
Shigella
Which of the following organisms are generally positive for Beta-galactosidase? -
Answer-E. coli
In the Kauffmann-White schema, the combined antigens used for serological
identifications of Salmonella spp. are: - Answer-O, Vi and H antigens
The drugs of choice for treatment of infections with Enterobacteriacea are: - Answer-
Aminoglycosides, trimethoprim-sulfamethoxazole, and third-generation cephalosporins.
