Exam 3 - (CH 19) Enterobacterales Textbook Review Questions

Question 1

Which genus is not a member of the resident microbiota of the human gastrointestinal tract?
A. Escherichia
B. Yersinia
C. Proteus
D. Citrobacter

Answer 1

B. Yersinia

Question 2

Which of the following is an Escherichia coli virulence factor that allows the bacterial cell to chelate iron?
A. Cytolysins
B. Shiga-like toxin
C. M protein
D. Aerobactin

Answer 2

D. Aerobactin

Question 3

What organism is most likely given the following results?
1. Motile
2. Lysine decarboxylase negative
3. Ornithine decarboxylase positive
4. Arginine dihydrolase positive
A. Shigella flexneri
B. Klebsiella pneumoniae subsp. pneumoniae
C. Enterobacter cloacae
D. Enterobacter aerogenes

Answer 3

C. Enterobacter cloacae

Question 4

The shigellae lack this group of antigens.
A. H
B. K
C. O
D. All of the above

Answer 4

A. H

Question 5

Which statement is true of Yersinia pestis?
A. It is a gram-variable bacillus that grows best at 37°C.
B. It is a long, chaining gram-negative bacillus that grows best at 4°C.
C. It is a bipolar staining gram-negative bacillus that grows best at 25 to 30°C.
D. It is a large, plump, bacillus that is motile at 25°C, but not nonmotile at 35°C.

Answer 5

C. It is a bipolar staining gram-negative bacillus that grows best at 25 to 30°C.

Question 6

Which of the following is true of all Klebsiella spp.?
A. All are methyl red positive and Voges-Proskauer negative.
B. No known species produce H2S.
C. No known species grow in potassium cyanide broth.
D. All are nonmotile.

Answer 6

B. No known species produce H2S.

Question 7

Which color and pigment is associated with Serratia marcescens?
A. Yellow xanthophyll
B. Yellow echineone
C. Orange tetraterpenoid
D. Red prodigiosin

Answer 7

D. Red prodigiosin

Question 8

Which biochemical characteristic is the most indicative of Hafnia?
A. Nitrate reduction positive
B. Oxidase negative
C. Delayed positive citrate
D. Malonate positive

Answer 8

C. Delayed positive citrate

Question 9

Which set of tests would help differentiate between Proteus vulgaris and Proteus mirabilis?
A. Indole and ornithine decarboxylase
B. Nitrate and oxidase
C. Lactose fermentation and urea
D. H2S production and sucrose fermentation

Answer 9

A. Indole and ornithine decarboxylase

Question 10

Providencia alcalifaciens can be differentiated from Providencia stuartii because it produces acid from this compound.
A. Salicin.
B. Adonitol.
C. Maltose.
D. Xylose a.

Answer 10

B. Adonitol.

Question 11

Which of the following describes Edwardsiella tarda?
A. Positive for urea, lysine decarboxylase, and indole
B. Positive for H2S and urea
C. Negative for urea and positive for lysine decarboxylase
D. Negative for urea and lysine decarboxylase, positive for indole

Answer 11

C. Negative for urea and positive for lysine decarboxylase

Question 12

Plesiomonas shigelloides is different from most Enterobacteriaceae in that it
A. does not produce gas from glucose and is oxidase positive.
B. is resistant to agent O/129.
C. does not reduce nitrate or grow in the presence of oxygen.
D. form a capsule or ferment any sugars.

Answer 12

A. does not produce gas from glucose and is oxidase positive.

Question 13

Which statement is true of most species of Kluyvera?
A. They produce a violet pigment.
B. They resemble Escherichia coli growing on MacConkey (MAC) agar.
C. They do not exhibit a zone of inhibition around a carbenicillin disk.
D. They are indole negative.

Answer 13

B. They resemble Escherichia coli growing on MacConkey (MAC) agar

Question 14

All fecal specimens should be routinely screened for
A. Salmonella, Shigella, and Campylobacter.
B. Yersinia, Aeromonas, and Vibrio.
C. enterohemorrhagic Escherichia coli (EHEC), enteropathogenic Escherichia coli (EPEC), and Yersinia.
D. Plesiomonas and Aeromonas.

Answer 14

A. Salmonella, Shigella, and Campylobacter.

Question 15

When evaluating a stool culture for pathogens, an oxidase test should be performed
A. only on lactose fermenters and gram-positive rods.
B. on colonies grown on chocolate agar only.
C. on colonies grown on MAC agar or eosin-methylene blue (EMB) agar.
D. on young colonies of nonlactose fermenters growing on sheep blood agar (SBA).

Answer 15

D. on young colonies of nonlactose fermenters growing on sheep blood agar (SBA).

Question 16

What are the three general characteristics a gram-negative bacillus must possess to belong to the family Enterobacteriaceae (with a few exceptions)?

Answer 16

Most members of the family Enterobacteriaceae are able to ferment glucose, are oxidase-negative (except for Plesiomonas shigelloides), and are able to reduce nitrate to nitrite (except for Photorhabdus spp. and Xenorhabdus spp.).

Question 17

Match the Shigella spp. with the corresponding group antigen: A, B, C, and D.
S. sonnei
S. boydii
S. dysenteriae
S. flexneri

Answer 17

S. sonnei (D)
S. boydii (C)
S. dysenteriae (A)
S. flexneri (B)

Question 18

Which of the following test results is most helpful in categorizing an isolate as a member of the tribe Proteeae?
a. Positive urea
b. Positive Voges-Proskauer
c. Positive phenylalanine deaminase
d. Positive lactose fermentation

Answer 18

c. Positive phenylalanine deaminase

Question 19

The causative agent of plague is most often transmitted to humans by:
a. Fleas
b. Mosquitos
c. Dog bites
d. Inhalation

Answer 19

a. Fleas

Question 20

A 47-year-old patient who had just returned from Mexico was admitted to the hospital with a 3-day history of vomiting and diarrhea, without fever, and no fecal leukocytes were found in the stool. When he was admitted to the hospital, a stool culture grew an organism identified as Escherichia coli. Which of the following strains is the most likely cause of the infection?
a. EPEC
b. ETEC
c. EHEC
d. EIEC

Answer 20

b. ETEC

Question 21

A gram-negative, oxidase-negative coccobacillus was isolated from the cerebrospinal fluid of an infant in the newborn nursery. The organism produced dark pink colonies on MAC agar and had the following biochemical results: triple sugar iron, acid over acid with gas; phenylalanine deaminase-negative; sulfide-indole-motility agar, H2S-negative, indole-positive, and motile; urease-negative; and citrate-negative. The most probable identity of this organism is:
a. Escherichia coli
b. Enterobacter aerogenes
c. Klebsiella pneumoniae
d. Serratia marcescens

Answer 21

a. Escherichia coli

Question 22

What organism is often associated with lobar pneumonia in elderly hospitalized patients?
a. Shigella spp.
b. Proteus vulgaris
c. Escherichia coli
d. Klebsiella pneumoniae

Answer 22

d. Klebsiella pneumoniae

Question 23

The most common cause of community-acquired UTIs is:
a. Klebsiella pneumoniae
b. Escherichia coli
c. Providencia stuartii
d. Citrobacter freundii

Answer 23

b. Escherichia coli

Question 24

Which organism is an opportunistic pathogen that causes wound and urinary tract infections and may cause the production of kidney stones?
a. Yersinia enterocolitica
b. Citrobacter freundii
c. Proteus mirabilis
d. Enterobacter cloacae

Answer 24

c. Proteus mirabilis

Question 25

An enteric organism that is acquired by eating improperly prepared and cooked or preserved food contaminated with human feces and produces dysentery is:
a. P. vulgaris
b. Y. enterocolitica
c. S. marcescens
d. Shigella spp.

Answer 25

d. Shigella spp.

Question 26

Points to Remember

Answer 26

■ Nearly any of the genera discussed in this chapter could conceivably be isolated from almost any clinical specimen, especially when dealing with immunocompromised patients.
■ Although most isolates of E. coli are considered normal fecal microbiota, several strains (diarrheogenic E. coli) are known to cause intestinal tract infections, in the United States EHEC is the most notable. E. coli is the most significant cause of UTIs.
■ Salmonella and Shigella are enteric pathogens and are not considered normal fecal biota.
■ Yersinia pestis, one of the most virulent species in the family Enterobacteriaceae, causes the extraintestinal infection plague.
■ A good patient history combined with proper selective screening agar (e.g., HE, XLD, and SMAC agars) can be very helpful in a timely and accurate identification of enteric pathogens associated with diarrheal disease.
■ The use of an initial battery of selective agar media and key biochemical tests that include an oxidase test, TSI, urea, and lysine iron agar (LIA) can often result in a presumptive genus identification that can be confirmed with either conventional biochemical tests, one of several multitest or rapid and automated identification systems, or a molecular biology assay.
■ Serogrouping is an important aspect in the identification of enteric pathogens.