Question 1

Which of the following agars is not selective for Enterobacteriaceae?

Accepted Answer

A) Buffered charcoal yeast extract 
B) MacConkey 
C) Hektoen enteric 
D) Xylose-lysine deoxycholate 
A) Buffered charcoal yeast extract 
B) MacConkey 
C) Hektoen enteric 
D) Xylose-lysine deoxycholate

Question 2

What two bacteria produce swarming colonies on nonselective media, such as sheep blood agar (SBA)?

Accepted Answer

A) Enterobacter aerogenes and Serratia marcescens 
B) Proteus pannier and Klebsiella pneumoniae 
C) P.vulgaris and P.mirabilis 
D) P.mirabilis and Escherichia coli 
A) Enterobacter aerogenes and Serratia marcescens 
B) Proteus pannier and Klebsiella pneumoniae 
C) P.vulgaris and P.mirabilis 
D) P.mirabilis and Escherichia coli

Question 3

A microbiologist is reading a stool culture and notices a very moist and mucoid pink colony on MacConkey agar.What is the most likely organism?

Accepted Answer

A) Klebsiella pneumoniae 
B) Escherichia coli 
C) Proteus vulgaris 
D) Acinetobacter 
A) Klebsiella pneumoniae 
B) Escherichia coli 
C) Proteus vulgaris 
D) Acinetobacter

Question 4

The Escherichia coli serotype O157:H7 is associated with all the following except:

Accepted Answer

A) hemorrhagic diarrhea. 
B) colitis. 
C) liver damage. 
D) hemolytic-uremic syndrome. 
A) hemorrhagic diarrhea. 
B) colitis. 
C) liver damage. 
D) hemolytic-uremic syndrome.

Question 5

In the carrier state, where are pathogenic salmonella carried?

Accepted Answer

A) Gallbladder 
B) Liver 
C) Intestines 
D) Stomach 
A) Gallbladder 
B) Liver 
C) Intestines 
D) Stomach

Question 6

Why is it that most cases of salmonella food poisoning are not treated with antibiotics?

Accepted Answer

A) The organisms are very resistant to antibiotics. 
B) Antibiotics cannot reach the organisms, because they are deeply embedded in the intestinal walls. 
C) Antibiotics would only kill the bacteria, then release the endotoxins into the blood, making things worse. 
D) The disease is self-limiting and will subside on its own. 
A) The organisms are very resistant to antibiotics. 
B) Antibiotics cannot reach the organisms, because they are deeply embedded in the intestinal walls. 
C) Antibiotics would only kill the bacteria, then release the endotoxins into the blood, making things worse. 
D) The disease is self-limiting and will subside on its own.

Question 7

What are the primary antigens used in serologic grouping of salmonellae?

Accepted Answer

A) Somatic A antigen and flagellar O antigens 
B) Capsular A antigen and somatic O antigen 
C) Flagellar H antigen and capsular A antigen 
D) Flagellar H antigen and somatic O antigen 
A) Somatic A antigen and flagellar O antigens 
B) Capsular A antigen and somatic O antigen 
C) Flagellar H antigen and capsular A antigen 
D) Flagellar H antigen and somatic O antigen

Question 8

All the following are biochemical features of Salmonella except:

Accepted Answer

A) lactose positive. 
B) indole negative. 
C) hydrogen sulfide positive. 
D) Voges-Proskauer (VP) negative. 
A) lactose positive. 
B) indole negative. 
C) hydrogen sulfide positive. 
D) Voges-Proskauer (VP) negative.

Question 9

Why can direct microscopy not be used to provide a presumptive identification of the enteric bacteria?

Accepted Answer

A) Some members of the genus Gram stain weakly. 
B) The microscopic characteristics are indistinguishable from other gram-negative bacteria. 
C) Some members of the genus do not decolorize well and appear gram-positive. 
D) Some members have very thick capsules, and these do not allow the penetration of the Gram stain. 
A) Some members of the genus Gram stain weakly. 
B) The microscopic characteristics are indistinguishable from other gram-negative bacteria. 
C) Some members of the genus do not decolorize well and appear gram-positive. 
D) Some members have very thick capsules, and these do not allow the penetration of the Gram stain.

Question 10

What organism possesses the Vi antigen?

Accepted Answer

A) Salmonella typhi 
B) S.sonnei 
C) Shigella sonnei 
D) Citrobacter freundii 
A) Salmonella typhi 
B) S.sonnei 
C) Shigella sonnei 
D) Citrobacter freundii

Exam 19: Enterobacteriaceae

Which of the following agars is not selective for Enterobacteriaceae?

What two bacteria produce swarming colonies on nonselective media, such as sheep blood agar (SBA)?

A microbiologist is reading a stool culture and notices a very moist and mucoid pink colony on MacConkey agar.What is the most likely organism?

The Escherichia coli serotype O157:H7 is associated with all the following except:

In the carrier state, where are pathogenic salmonella carried?

Why is it that most cases of salmonella food poisoning are not treated with antibiotics?

What are the primary antigens used in serologic grouping of salmonellae?

All the following are biochemical features of Salmonella except:

Why can direct microscopy not be used to provide a presumptive identification of the enteric bacteria?

What organism possesses the Vi antigen?

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Use of Colony Morphology for the Presumptive Identification of Microorganisms

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