Deck 19: Enterobacteriaceae

Question 1

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

Answer 1

A
E.coli is widely recognized as the most common cause of urinary tract infections in humans.The E.coli strains that cause UTIs usually originate in the large intestine as resident or transient flora and may exist either as the predominant E.coli population or as a small part of the E.coli strains in the large intestine.

Question 2

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

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

Answer 2

C
On certain selective and differential media, such as MacConkey or EMB agars, E.coli has distinctive morphology.It usually presents as a lactose-positive (pink) colony with a surrounding area of precipitated bile salts on MacConkey agar.On EMB agar, it presents with a green metallic sheen.

Question 3

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

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

Answer 3

C
P.mirabilis and P.vulgaris are easily identified in the clinical laboratory because of their characteristic colony morphology.Both species produce swarming colonies on nonselective media, such as SBA.This characteristic swarming is a result of a tightly regulated cycle of differentiation from standard vegetative cells (swimmers) to hyperflagellated, elongated, polyploid cells (swarmers) capable of coordinated surface movement.

Question 4

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

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

Question 5

This genus currently has only one species associated with it that has been implicated in urinary tract infections.What is the name of this organism?

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

Question 6

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

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

Question 7

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 8

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 9

All the following are biochemical features of Salmonella except:

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

Question 10

What genus of bacteria is considered an opportunistic pathogen often associated with nosocomial outbreaks?

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

Question 11

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 12

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 13

What substance, when 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 14

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.

Question 15

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

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

Question 16

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?

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

Question 17

Which animals are a common source of Salmonella serotypes?

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

Question 18

All of the following are members of the Citrobacter genus except:

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

Question 19

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

Question 20

Which of the following agars is not selective for Enterobacteriaceae?

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

Question 21

What organism possesses the Vi antigen?

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

Question 22

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 23

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

Question 24

In the carrier state, where are pathogenic salmonella carried?

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

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

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

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

Question 27

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 28

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

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

Question 29

What bacterium is the causative agent of the plague?

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

Question 30

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.