Deck 21: Enterobacteriaceae

Question 1

Which of the following characteristics has recently changed when defining the family Enterobacteriaceae?

A) Gram-negative rods
B) Ferment glucose
C) Reduce nitrates to nitrites
D) Oxidase negative

Answer 1

Oxidase negative

Question 2

Which of the following antigens remains after boiling a suspension of a member of the Enterobacteriaceae for 10 minutes?

A) K
B) O
C) H
D) Vi

Answer 2

O

Question 3

Which of the following properties or reactions consistently differentiates gram-negative rods of the Enterobacteriaceae from the non-fermenting gram-negative rods?

A) Growth on MacConkey
B) TSI reaction of K/A or A/A
C) Oxidase reaction
D) Presence of LPS

Answer 3

TSI reaction of K/A or A/A

Question 4

Phenylalanine deaminase is produced by all of the following organisms except

A) Proteus vulgaris.
B) Morganella morganii.
C) Serratia marcescens.
D) Providencia stuartii.

Question 5

Which genera of the Enterobacteriaceae are considered enteric pathogens?

A) Enterobacter, Providencia, and Proteus
B) Enterobacter, Citrobacter, and Morganella
C) E. coli, Citrobacter, and Klebsiella
D) Yersinia, Salmonella, and Shigella

Question 6

Given the presence of blood and white blood cells in stool, which of the following organisms is the most likely pathogen?

A) non-motile, urea-negative, non-lactose fermenter.
B) H₂S-positive, lysine-positive, citrate-negative, non-lactose fermenter.
C) H₂S-positive, lysine-positive, citrate-positive, non-lactose fermenter.
D) PAD-positive, urea-positive non-lactose fermenter.

Question 7

All of the following organisms are commonly associated with urinary tract infections except a

A) VP-negative, citrate-negative, indole-positive, lactose fermenter.
B) H₂S-positive, urea-negative, lysine-positive, non-lactose fermenter.
C) H₂S-positive, urea-positive, indole-negative, non-lactose fermenter.
D) non-motile, VP-positive, indole-negative, lactose fermenter.

Question 8

Pus collected from a draining axillary lymph node is sent to the laboratory. A gramnegative rod is observed on Gram stain. Twenty-four hours after incubation at 35°C in CO2, a poorly growing non-lactose fermenter is observed. After 48 hours, the colonies on BAP and MAC were slightly larger. The organism proved to be

$\begin{array}{ll} \text {Motility at \( 35^{\circ} \mathrm{C} \) : negative}& \text {Urea: no color change}\\ \text {Motility at \( 25^{\circ} \mathrm{C} \) : negative}& \text {PAD: no color change}\\ \text {VP: no color change}&\text {Lysine and Ornithine: no color change}\\ \text {Indole: no color change}&\text {TSI: red slant and yellow butt}\\\end{array}$

Citrate: green
This organism is the causative agent of

A) typhoid fever.
B) gastroenteritis.
C) plague.
D) mesenteric lymph adenitis.

Question 9

The lipopolysaccharide associated with the Enterobacteriaceae is

A) used in conjugation.
B) part of the plasma membrane.
C) protective against antimicrobial agents.
D) an endotoxin.

Question 10

Which of the following reactions is associated with the gram-negative rod best known for its capsule production?

A) Positive motility
B) H₂S production
C) VP positive
D) PAD positive

Question 11

A beta-hemolytic, lactose fermenter is isolated in pure culture from catheterized urine of an 88-year-old female. What additional spot or rapid test result is necessary to presumptively identify this organism?

A) Indole negative
B) Indole positive
C) MUG negative
D) Oxidase positive

Question 12

A voided urine culture from a 46-year-old female grows dark lactose fermenting as well as non-lactose fermenting colonies. The BAP shows gray, beta-hemolytic colonies under a swarming film of growth. The microbiologist performs a spot indole test on swarming colony and it is positive. She reports the organism as presumptive Proteus vulgaris using the department's rapid identification criteria. The next day the second colony identifies as E. coli using a commercial identification system. Your next step in this process is to

A) report Proteus vulgaris and E. coli isolated.
B) question the identification of the E. coli colony and repeat testing.
C) identify the non-lactose fermenting,, swarming colony using a commercial identification system.
D) repeat the identification of both organisms using a commercial identification system.

Question 13

A stool culture from an 11-month-old male suffering from bloody diarrhea gave the following results on differential enteric media:
MacConkey agar: clear colonies
Xylose Lysine Deoxycholate agar: clear colonies
Hecktoen Enteric agar: clear colonies
Which of the following tests must be performed to confirm the final identification of
This enteric pathogen?

A) Salmonella serotyping
B) Shigella serotyping
C) Latex agglutination for E. coli O157:H7
D) No further testing is required

Question 14

A black colony on HE and XLD agars, isolated from a stool culture, produces the following biochemical reactions:
$\begin{array}{ll} \text {Motility at \( 25^{\circ} \mathrm{C} \) : positive}& \text {PAD: no color change}\\ \text {Motility at \( 35^{\circ} \mathrm{C} \) : positive}& \text {Indole: no color change}\\ \text {Urea: no color change}&\text {VP: no color change}\\ \end{array}$

If this organism is a strict pathogen, you expect it to also be

A) citrate positive and lysine positive
B) citrate negative and lysine positive.
C) citrate positive and lysine negative.
D) citrate negative and lysine negative.

Question 15

One of the most resistant genus and species of the Enterobacteriaceae is a

A) beta-hemolytic, indole-positive, lactose fermenter.
B) swarming, indole-negative, non-lactose fermenter.
C) nonmotile, VP-negative, non-lactose fermenter.
D) VP-positive, nonmotile, indole-negative, lactose fermenter.

Question 16

Which of the following organisms always requires antibiotic therapy when isolated in a stool culture?

A) Salmonella spp.
B) Shigella spp.
C) Salmonella typhi
D) Edwardsella tarda

Question 17

A 25-year-old female complained of burning on urination. The urine culture grew a clear colony on MacConkey agar. Biochemical testing revealed the following: This organism will also

A) swarm.
B) need to be serotyped.
C) appear as a mucoid colony.
D) exhibit multiple antibiotic resistance.

Question 18

An 8-year-old female was admitted with a complaint of right lower quadrant pain. She was taken to surgery for removal of her appendix. The appendix appeared normal, but lymph nodes in the peritoneal cavity were inflamed. Cultures of the nodes were taken and sent to the microbiology department. The organism that grew appeared as clear colonies on MAC and provided the following reactions: This is organism will also produce

A) bulls-eye colonies on CIN agar.
B) DNase.
C) clear colonies on XLD agar.
D) lipase.

Question 19

A sputum from a cancer patient grew a pink colony on MAC. The biochemical reactions were as follows:
What colony characteristic is often associated with this organism?

A) Swarmer
B) Yellow pigment
C) Red pigment
D) Mucoid

Question 20

A pink colony on MAC grew from an abdominal wound. The biochemical reactions included:
The organism identified is

A) serologically similar to Salmonella spp.
B) often found hiding in the gallbladder in carriers.
C) characterized by the production of the Vi antigen.
D) able to produce only a small amount of H₂S in TSI.