Deck 19: Enterobacteriaceae

Question 1

What genus has the following characteristics: urea negative, positive for lysine decarboxylase, hydrogen sulfide, and indole, and does not grow on Simmon's citrate?

A) Providencia
B) Edwardsiella
C) Escherichia
D) Morganella

Answer 1

B

Question 2

You have isolated a bacterium from a stool culture that produces clear colonies on sorbitol MacConkey (SMAC) agar. Which of the following would be the most appropriate test to perform next?

A) Gram stain
B) Oxidase
C) Rapid methylumbelliferyl-b-D-glucuronide (MUG)
D) Rapid urease

Answer 2

C

Question 3

What organism in the genus Providencia is incriminated in nosocomial outbreaks in burn units and has been isolated from urine cultures?

A) Providencia stuartii
B) P. heimbachae
C) P. rustigianii
D) P. alcalifaciens

Answer 3

A

Question 4

What substance produced by the Salmonella spp., which cause gastroenteritis, has been implicated as a significant virulence factor?

A) Hyaluronidase
B) Protease
C) Enterotoxin
D) Endotoxin

Question 5

What is the name of the organism that has been a documented cause of nursery outbreaks of neonatal meningitis and brain abscesses?

A) Citrobacter freundii
B) C. asteroides
C) C. braakii
D) C. koseri

Question 6

The primary pathogens of the Enterobacteriaceae include all the following, except

A) Salmonella enterica.
B) Proteus mirabilis.
C) Shigella spp.
D) Yersinia spp.

Question 7

Which of the following agars is not selective for Enterobacteriaceae?

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

Question 8

All of the following are categories of diarrhea-causing Escherichia coli, except

A) ETEC.
B) EMEC.
C) EIEC.
D) EPEC.

Question 9

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

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 10

What organism presents as a pink colony with a halo on MAC agar and a green metallic sheen on eosin methylene blue (EMB) agar?

A) Salmonella enterica
B) Proteus mirabilis
C) Escherichia coli
D) Klebsiella pneumonia

Question 11

The most important cause of UTIs is

A) Klebsiella pneumoniae.
B) Escherichia coli.
C) Hafnium alvei.
D) Morganella morganii.

Question 12

Which organism is the most common cause of urinary tract infections (UTIs) in humans?

A) Escherichia coli
B) Klebsiella oxytoca
C) Proteus mirabilis
D) Enterobacter cloacae

Question 13

A DNase-positive member of the family Enterobacteriaceae is suggestive of

A) Enterobacter.
B) Serratia.
C) Proteus.
D) Escherichia.

Question 14

All the following are biochemical features of Salmonella, except

A) lactose positive.
B) indole negative.
C) hydrogen sulfide positive.
D) VP negative.

Question 15

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

A) Klebsiella pneumoniae
B) Escherichia coli
C) Proteus vulgaris
D) Yersinia enterocolitica

Question 16

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

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

Question 17

Which animals are a common source of Salmonella serotypes?

A) Dogs
B) Cold-blooded animals (fish)
C) Cats
D) Horses

Question 18

Escherichia coli strains have all the following properties, except

A) indole production.
B) fermentation of glucose and lactose.
C) methyl red (MR) positive, Voges-Proskauer (VP) negative.
D) can use citrate as a sole carbon source.

Question 19

What bacterium produces swarming colonies on nonselective media, such as sheep blood agar (SBA)?

A) Enterobacter aerogenes
B) Klebsiella pneumoniae
C) P. mirabilis
D) Morganella morganii

Question 20

All of the following are clinically significant isolates of the genus Enterobacter, except

A) Enterobacter cloacae.
B) E. aerogenes.
C) E. gergoviae.
D) E. hartmanni.

Question 21

A microbiologist is reading stool culture plates. She sees an organism that has a dry, pink colony with a surrounding "halo" of pink on MAC. What is a good presumptive identification of this organism?

A) Enteric pathogen
B) Escherichia/Citrobacter-like organism
C) Klebsiella/Enterobacter-like organism
D) Haemophilus influenzae

Question 22

In the carrier state, where are pathogenic salmonella carried?

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

Question 23

What enteric organism may produce a blue-violet pigment on non-blood-containing media?

A) Kluyvera
B) Shigella
C) Ewingella
D) Cedecea

Question 24

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

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 25

Bacillary dysentery caused by this organism is marked by penetration of intestinal epithelial cells following attachment of the organisms to mucosal surfaces, local inflammation, shedding of the intestinal lining, and formation of ulcers that follow the epithelial penetration. What is this organism?

A) Enterobacter
B) Citrobacter
C) Shigella
D) Salmonella

Question 26

A microbiologist is reading stool culture plates. She is looking for enteric pathogens on the MAC plate. What do they look like?

A) Clear, colorless colonies
B) Large, bright pink colonies
C) Small, mucoid, green colonies
D) Small, orange colonies

Question 27

What bacterium is the causative agent of the plague?

A) Salmonella enteritidis
B) Citrobacter freundii
C) Shigella sonnei
D) Yersinia pestis

Question 28

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

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 29

All of the following are symptoms of salmonellosis that may appear 8 to 36 hours after ingestion of contaminated food, except

A) nausea.
B) vomiting.
C) headache.
D) watery diarrhea.

Question 30

What organism possesses the Vi antigen?

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

Question 31

A microbiologist is reading stool culture plates. She sees an organism that has a large, mucoid pink colony on MAC. What is a good presumptive identification of this organism?

A) Enteric pathogen
B) Escherichia/Citrobacter-like organism
C) Klebsiella/Enterobacter-like organism
D) Haemophilus influenzae

Question 32

All of the following are characteristics of Shigella spp., except

A) nonmotile.
B) urea positive.
C) hydrogen sulfide negative.
D) lysine decarboxylase negative.

Question 33

What disease produced by a Salmonella spp. is a severe form of enteric fever?

A) Pontiac fever
B) Typhoid fever
C) Undulant fever
D) Malignant fever