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ENTERO Flashcards

1
Q

Biochemically, the Enterobacteriaceae are gram-negative rods that:

A. Ferment glucose, reduce nitrate to nitrite, and are oxidase negative
B. Ferment glucose, produce indophenol oxidase, and form gas
C. Ferment lactose and reduce nitrite to nitrogen gas
D. Ferment lactose and produce indophenol oxidase

A

A. Ferment glucose, reduce nitrate to nitrite, and
are oxidase negative

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2
Q

The ortho-nitrophenyl-β-galactopyranoside (ONPG) test is most useful when differentiating:

A. Salmonella spp. from Pseudomonas spp.
B. Shigella spp. from some strains of Escherichia coli
C. Klebsiella spp. from Enterobacter spp.
D. Proteus vulgaris from Salmonella spp.

A

B. Shigella spp. from some strains of Escherichia coli

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3
Q

The Voges-Proskauer (VP) test detects which end product of glucose fermentation?

A. Acetoin
B. Nitrite
C. Acetic acid
D. Hydrogen sulfide

A

A. Acetoin

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4
Q

At which pH does the methyl red (MR) test become positive?

A. 7.0
B. 6.5
C. 6.0
D. 4.5

A

D. 4.5

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5
Q

A positive Simmons citrate test is seen as a:

A. Blue color in the medium after 24 hours of incubation at 35°C
B. Red color in the medium after 18 hours of incubation at 35°C
C. Yellow color in the medium after 24 hours of incubation at 35°C
D. Green color in the medium after 18 hours of incubation at 35°C

A

A. Blue color in the medium after 24 hours of incubation at 35°C

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6
Q

In the test for urease production, ammonia reacts to form which product?

A. Ammonium citrate
B. Ammonium carbonate
C. Ammonium oxalate
D. Ammonium nitrate

A

B. Ammonium carbonate

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7
Q

Which of the following reagents is added to detect the production of indole?

A. p-Dimethylaminobenzaldehyde
B. Bromcresol purple
C. Methyl red
D. Cytochrome oxidase

A

A. p-Dimethylaminobenzaldehyde

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8
Q

Decarboxylation of the amino acids lysine, ornithine, and arginine results in the formation of:

A. Ammonia
B. Urea
C. CO2
D. Amines

A

D. Amines

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9
Q

Lysine iron agar (LIA) showing a purple slant and a blackened butt indicates:

A. E. coli
B. Citrobacter spp.
C. Salmonella spp.
D. Proteus spp.

A

C. Salmonella spp.

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10
Q

Putrescine is an alkaline amine product of which bacterial enzyme?

A. Arginine decarboxylase
B. Phenylalanine deaminase
C. Ornithine decarboxylase
D. Lysine decarboxylase

A

C. Ornithine decarboxylase

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11
Q

Which genera are positive for phenylalanine deaminase?

A. Enterobacter, Escherichia, and Salmonella
B. Morganella, Providencia, and Proteus
C. Klebsiella and Enterobacter
D. Proteus, Escherichia, and Shigella

A

B. Morganella, Providencia, and Proteus

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12
Q

Kligler iron agar (KIA) differs from triple-sugar iron agar (TSI) in the:

A. Ratio of lactose to glucose
B. Ability to detect H2S production
C. Use of sucrose in the medium
D. Color reaction denoting production of acid

A

C. Use of sucrose in the medium

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13
Q

The malonate test is most useful in differentiating which members of the Enterobacteriaceae?

A. Shigella
B. Proteus
C. Salmonella subgroups 2, 3 (the former Arizona)
D. Serratia

A

C. Salmonella subgroups 2, 3 (the former Arizona)

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14
Q

Which genera of the Enterobacteriaceae are known to cause diarrhea and are considered enteric pathogens?

A. Enterobacter, Klebsiella, Providencia, and Proteus
B. Escherichia, Salmonella, Shigella, and Yersinia
C. Pseudomonas, Moraxella, Acinetobacter, and Aeromonas
D. Enterobacter, Citrobacter, and Morganella

A

B. Escherichia, Salmonella, Shigella, and Yersinia

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15
Q

An isolate of E. coli recovered from the stool of a patient with severe bloody diarrhea should be tested for which sugar before sending it to a reference laboratory for serotyping?

A. Sorbitol (fermentation)
B. Mannitol (oxidation)
C. Raffinose (fermentation)
D. Sucrose (fermentation)

A

A. Sorbitol (fermentation)

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16
Q

Care must be taken when identifying biochemical isolates of Shigella because serological cross reactions occur with:

A. E. coli
B. Salmonella spp.
C. Pseudomonas spp.
D. Proteus spp.

A

A. E. coli

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17
Q

Which species of Shigella is most commonly associated with diarrheal disease in the United States?

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

A

D. S. sonnei

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18
Q

Which of the following tests best differentiates Shigella species from E. coli?

A. Hydrogen sulfide, VP, citrate, and urease
B. Lactose, indole, ONPG, and motility
C. Hydrogen sulfide, MR, citrate, and urease
D. Gas, citrate, and VP

A

B. Lactose, indole, ONPG, and motility

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19
Q

Which genera of Enterobacteriaceae are usually nonmotile at 36°C?

A. Shigella, Klebsiella, and Yersinia
B. Escherichia, Edwardsiella, and Enterobacter
C. Proteus, Providencia, and Salmonella
D. Serratia, Morganella, and Hafnia

A

A. Shigella, Klebsiella, and Yersinia

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20
Q

Fever, abdominal cramping, watery stools, and fluid and electrolyte loss preceded by bloody stools 2-3 days before is characteristic of shigellosis but may also result from infection with:

A. Campylobacter spp.
B. Salmonella spp.
C. Proteus spp.
D. Yersinia spp.

A

A. Campylobacter spp.

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21
Q

Cold enrichment of feces (incubation at 4°C) in phosphate-buffered saline prior to subculture onto enteric media enhances the recovery of:

A. Enterotoxigenic E. coli
B. Salmonella paratyphi
C. Hafnia alvei
D. Y. enterocolitica

A

D. Y. enterocolitica

22
Q

Which group of tests, along with colonial morphology on primary media, aids most in the rapid identification of the Enterobacteriaceae?

A. MR and VP, urease, and blood agar plate
B. Phenylalanine deaminase, urease, and CDC agar plate
C. Bacitracin, β-lactamase, and MacConkey agar plate
D. Indole, oxidase, MacConkey, and blood agar plates

A

D. Indole, oxidase, MacConkey, and blood agar
plates

23
Q

A routine, complete stool culture procedure should include media for the isolation of E. coli O157:H7 as well as:

A. Salmonella, Shigella, Yersinia, Campylobacter, and Staphylococcus aureus
B. Vibrio cholerae, Brucella, and Yersinia spp.
C. S. aureus, group B streptococci, and group D streptococci
D. Clostridium difficile, Clostridium perfringens, and
Yersinia spp.

A

A. Salmonella, Shigella, Yersinia, Campylobacter,
and Staphylococcus aureus

24
Q

Which group of tests best identifies the Morganella and Proteus genera?

A. Motility, urease, and phenylalanine deaminase
B. Malonate, glucose fermentation, and deoxyribonuclease (DNase)
C. Indole, oxidase, MR, and VP
D. Indole, citrate, and urease

A

A. Motility, urease, and phenylalanine deaminase

25
Q

Which group of tests best differentiates Enterobacter aerogenes from Edwardsiella tarda?

A. Motility, citrate, and urease
B. Hydrogen sulfide (H2S) production, sucrose fermentation, indole, and VP
C. Lysine decarboxylase, urease, and arginine dihydrolase
D. Motility, H2S production, and DNase

A

B. Hydrogen sulfide (H2S) production, sucrose
fermentation, indole, and VP

26
Q

Enterobacter sakazakii can best be differentiated from Enterobacter cloacae by which of the following characteristics?

A. Yellow pigmentation and negative sorbitol fermentation
B. Pink pigmentation and positive arginine dihydrolase
C. Yellow pigmentation and positive urease
D. H2S production on TSI

A

A. Yellow pigmentation and negative sorbitol
fermentation

27
Q

Members of the genus Cedecea are best differentiated from Serratia spp. by which test result?

A. Positive motility
B. Positive urease
C. Positive phenylalanine deaminase
D. Negative DNase

A

D. Negative DNase

28
Q

Which of the following organisms is often confused with the Salmonella species biochemically and on plated media?

A. E. coli
B. Citrobacter freundii
C. Enterobacter cloacae
D. Shigella dysenteriae

A

B. Citrobacter freundii

29
Q

A gram-negative rod is recovered from a catheterized urine sample from a nursing home patient. The lactose-negative isolate tested positive for indole, urease, ornithine decarboxylase, and phenylalanine deaminase and negative for H2S. The most probable identification is:

A. Edwardsiella spp.
B. Morganella spp.
C. Ewingella spp.
D. Shigella spp.

A

B. Morganella spp.

30
Q

Which single test best separates Klebsiella oxytoca from K. pneumoniae?

A. Urease
B. Sucrose
C. Citrate
D. Indole

A

D. Indole

31
Q

Which of the following organisms, found in normal fecal flora, may be mistaken biochemically for the genus Yersinia?

A. Klebsiella spp.
B. Proteus spp.
C. E. coli
D. Enterobacter spp.

A

B. Proteus spp.

32
Q

Why might it be necessary for both pink (lactose-positive) and colorless (lactose-negative) colonies from an initial stool culture on MacConkey agar to be subcultured and tested further for possible pathogens?

A. Most Shigella strains are lactose positive
B. Most Salmonella strains are maltose negative
C. Most Proteus spp. are lactose negative
D. Pathogenic E. coli can be lactose positive or lactose negative

A

D. Pathogenic E. coli can be lactose positive or lactose negative

33
Q

Which agar that is used for routine stool cultures is the medium of choice for the isolation of Yersinia strains from stool specimens?

A. Salmonella-Shigella agar
B. Hektoen enteric agar
C. MacConkey agar
D. CNA agar

A

C. MacConkey agar

34
Q

Which organism is sometimes mistaken for Salmonella and will agglutinate in Salmonella polyvalent antiserum?

A. C. freundii strains
B. Proteus mirabilis strains
C. S. sonnei strains
D. E. coli

A

A. C. freundii strains

35
Q

A bloody stool cultured from a 26-year-old woman after 3 days of severe diarrhea showed the following results at 48 hours after being plated on the following media:
MacConkey agar: little normal flora with many non-lactose-fermenting colonies
Hektoen enteric agar: many blue-green colonies Campylobacter blood agar and C. difficile agar:
no growth
Clear colonies (from MacConkey agar) tested
negative for oxidase, indole, urease, motility,
and H2S
The most likely identification is:

A. Shigella spp.
B. Salmonella spp.
C. Proteus spp.
D. E. coli

A

A. Shigella spp.

36
Q

Which of the following organisms are generally positive for β-galactosidase?

A. Salmonella spp.
B. Shigella spp.
C. Proteus spp.
D. E. coli

A

D. E. coli

37
Q

In the Kauffmann-White schema, the combined antigens used for serological identification of the Salmonella spp. are:

A. O antigens
B. H antigens
C. Vi and H antigens
D. O, Vi, and H antigens

A

D. O, Vi, and H antigens

38
Q

The drugs of choice for treatment of infections with Enterobacteriaceae are:

A. Aminoglycosides, trimethoprim-sulfamethoxazole, third-generation cephalosporins
B. Ampicillin and nalidixic acid
C. Streptomycin and isoniazid
D. Chloramphenicol, ampicillin, and colistin

A

A. Aminoglycosides, trimethoprim-sulfamethoxazole,
third-generation cephalosporins

39
Q

The Shiga-like toxin (verotoxin) is produced mainly by which Enterobacteriaceae?

A. Klebsiella pneumoniae
B. E. coli
C. Salmonella typhimurium
D. Enterobacter cloacae

A

B. E. coli

40
Q

Infections caused by Yersinia pestis are rare in the United States. Those cases that do occur are most frequently located in which region?

A. New Mexico, Arizona, and California
B. Alaska, Oregon, and Utah
C. North and South Carolina and Virginia
D. Ohio, Michigan, and Indiana

A

A. New Mexico, Arizona, and California

41
Q

A leg culture from a nursing home patient grew gram-negative rods on MacConkey agar as pink to dark pink oxidase-negative colonies. Given the following results, which is the most likely organism?

TSI = A/A
VP = +
Urease = +
Indole = Neg
Citrate = +
Motility = Neg
MR = Neg
H2S = Neg

Antibiotic susceptibility: resistant to carbenicillin and ampicillin

A. Serratia marcescens
B. Proteus vulgaris
C. Enterobacter cloacae
D. Klebsiella pneumoniae

A

D. Klebsiella pneumoniae

42
Q

Four blood cultures were taken over a 24-hour period from a 20-year-old woman with severe diarrhea. The cultures grew motile (room temperature), gram-negative rods. A urine specimen obtained by catheterization also showed gram-negative rods, 100,000 col/mL. Given the following results, which is the most likely organism?

TSI = A/A gas
VP = Neg
H2S = Neg
Urease = Neg
Phenylalanine deaminase = Neg
Indole = +
MR = +
Citrate = Neg
Lysine decarboxylase = +

A. Proteus vulgaris
B. Salmonella typhi
C. Yersinia enterocolitica
D. E. coli

A

D. E. coli

43
Q

A stool culture from a 30-year-old man suffering from bloody mucoid diarrhea gave the following results on differential enteric media:
MacConkey agar = clear colonies;
XLD agar = clear colonies;
Hektoen agar = green colonies;
Salmonella-Shigella agar = small, clear colonies

Which tests are most appropriate for identification of this enteric pathogen?

A. TSI, motility, indole, urease, Shigella typing with polyvalent sera
B. TSI, motility, indole, lysine, Salmonella typing with polyvalent sera
C. TSI, indole, MR, VP, citrate
D. TSI, indole, MR, and urease

A

A. TSI, motility, indole, urease, Shigella typing with polyvalent sera

44
Q

A leg-wound culture from a hospitalized 70-year-old diabetic man grew motile, lactose-negative colonies on MacConkey agar. Given the following biochemical reactions at 24 hours, what is the most probable organism?

H2S (TSI) = Neg
MR = Neg
DNase = +
Urease = Neg
Phenylalanine deaminase = Neg
Ornithine and lysine decarboxylase = +
Arginine decarboxylase = Neg
Gelatin hydrolysis = +
Indole = Neg
VP = +
Citrate = +

A. Proteus vulgaris
B. Serratia marcescens
C. Proteus mirabilis
D. Enterobacter cloacae

A

B. Serratia marcescens

(Gelatin hydrolysis and DNase are positive for both the Proteus spp. and Serratia, but the negative urease and phenylalanine deaminase are differential.)

45
Q

Three blood cultures taken from a 30-year-old cancer patient receiving chemotherapy and admitted with a urinary tract infection grew lactose-negative, motile, gram-negative rods prior to antibiotic therapy. Given the following biochemical reactions, which is the most likely organism?

H2S (TSI) = +
VP = Neg
DNase = +
Gelatin hydrolysis = +
Ornithine decarboxylase = Neg
Indole = Neg
Citrate = Neg
Phenylalanine deaminase = +
MR = +
Urease = +

A. Proteus vulgaris
B. Proteus mirabilis
C. Serratia marcescens
D. Klebsiella pneumoniae

A

A. Proteus vulgaris

46
Q

Three consecutive stool cultures from a 25-year-old male patient produced scant normal fecal flora on MacConkey and Hektoen agars. However, colonies on CIN agar (cefsulodin-irgasan-novobiocin) displayed “bulls-eye” colonies after 48 hours incubation. The patient had been suffering from enterocolitis with fever, diarrhea, and abdominal pain for 2 days. What is the most likely identification of this gram-negative rod?

A. E. coli
B. Proteus mirabilis
C. Yersinia enterocolitica
D. Klebsiella pneumoniae

A

C. Yersinia enterocolitica

47
Q

A 6-year-old female patient was admitted to
the hospital following 2 days of severe diarrhea. Cultures from three consecutive stool samples contained blood and mucus. Patient history revealed a hamburger lunch at a fast-food restaurant 3 days earlier. Which pathogen is most likely responsible for the following results? Growth on:
XLD agar = yellow colonies
HE agar = yellow colonies
Mac agar = light pink and dark pink colonies Mac with sorbitol agar - few dark pink and many
colorless colonies

A. Salmonella spp.
B. Shigella spp.
C. E. coli O157:H7
D. Yersinia enterocolitica

A

C. E. coli O157:H7

48
Q

Following a 2-week camping trip to the Southwest (US), a 65-year-old male patient was hospitalized with a high fever and an inflammatory swelling of the axilla and groin lymph nodes. Several blood cultures were obtained, resulting in growth of gram-negative rods resembling “closed safety pins.” The organism grew on MacConkey’s agar showing non-lactose-fermenting colonies.
Testing demonstrated a nonmotile rod that was biochemically inert. What is the most likely identification?

A. Yersinia pestis
B. Klebsiella pneumoniae
C. Proteus vulgaris
D. Morganella morganii

A

A. Yersinia pestis

49
Q

The majority of clinical laboratories with a microbiology department should have the capability of serotyping which pathogenic Enterobacteriaceae?

A. Yersinia enterocolitica, Shigella spp.
B. E. coli O157:H7, Salmonella spp., Shigella spp.
C. Yersinia pestis, Salmonella spp.
D. Edwardsiella spp., Salmonella spp.

A

B. E. coli O157:H7, Salmonella spp., Shigella spp.

50
Q

Direct spread of pneumonic plague disease occurs by which route?

A. Fecal-oral route
B. Rat bite
C. Ingestion of contaminated tissue
D. Inhalation of contaminated airborne droplets

A

D. Inhalation of contaminated airborne droplets

51
Q

Which isolates of the Enterobacteriaceae family most commonly produce extended-spectrum β-lactamase (ESBL)?

A. E. coli and Klebsiella pneumoniae
B. Yersinia enterocolitica and Yersinia pestis
C. Morganella morganii and Proteus vulgaris
D. Salmonella typhi and Shigella sonnei

A

A. E. coli and Klebsiella pneumoniae

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