Exam 3 - (CH 20) Vibrio, Aeromonas, and Campylobacter Textbook Review Questions

Question 1

Vibrio parahaemolyticus can be serotyped by means of its

A. somatic and capsular antigens.
B. flagellar antigen.
C. hemagglutinin and neuraminidase.
D. capsular antigen.

Answer 1

A. somatic and capsular antigens.

Question 2

Which of the following set of results is true of Vibrio cholerae biogroup El Tor?

A. Hemolyzes erythrocytes, but does not agglutinate chicken red blood cells.
B. Voges-Proskauer negative and resistant to polymixin B.
C. Voges-Proskauer positive and inhibited by polymixin B.
D. Does not hemolyze erythrocytes and resistant to polymixin B.

Answer 2

C. Voges-Proskauer positive and inhibited by polymixin B.

Question 3

Which species is the most frequently encountered species in the United States?

A. Vibrio cholerae
B. Vibrio parahaemolyticus
C. Vibrio vulnificus
D. Vibrio cincinnatiensis

Answer 3

B. Vibrio parahaemolyticus

Question 4

Which positive test result distinguishes Vibrio spp. from Aeromonas?

A. String test
B. Inositol
C. Oxidase
D. Gram reaction

Answer 4

A. String test

Question 5

Which species is a psychrophilic aeromonad?

A. Aeromonas hydrophila
B. Aeromonas trota
C. Aeromonas veronii
D. Aeromonas salmonicida

Answer 5

D. Aeromonas salmonicida

Question 6

Which species is most frequently associated with diarrhea in the pediatric population and inflammatory bowel disease?

A. Aeromonas hydrophila
B. Aeromonas caviae
C. Aeromonas dhakensis
D. Aeromonas trota

Answer 6

B. Aeromonas caviae

Question 7

Which of the following traits could be responsible for Aeromonas being overlooked in a stool culture?

A. Aeromonads turn an oxidase test purple.
B. Many aeromonads appear pink on MacConkey (MAC) agar.
C. Aeromonads are mannitol positive.
D. Some aeromonads hydrolyze esculin.

Answer 7

B. Many aeromonads appear pink on MacConkey (MAC) agar.

Question 8

Which of the following is not associated with Helicobacter pylori?

A. Type B gastritis
B. Gastric carcinoma
C. Dysentery
D. Gastric ulcers

Answer 8

C. Dysentery

Question 9

Which of the following is a true statement regarding stool culture incubation at 42°C?

A. Campylobacter jejuni is inhibited.
B. Colon microbiota is inhibited.
C. Most Salmonella spp. and Campylobacter jejuni grow best at this temperature.
D. Campylobacter fetus subsp. fetus grows abundant large, yellow, mucoid colonies.

Answer 9

B. Colon microbiota is inhibited.

Question 10

Which organism would be most likely given the following results?
1. Gram-negative
2. Oxidase positive
3. Growth on thiosulfate citrate bile salt sucrose (TCBS) agar
4. Positive lysine decarboxylase
5. Acid produced from salicin

A. Aeromonas hydrophila
B. Vibrio cholerae
C. Campylobacter jejuni
D. Vibrio vulnificus

Answer 10

D. Vibrio vulnificus

Question 11

A gram-negative bacillus isolated from a stool specimen produces clear colonies on MacConkey agar and yellow colonies on thiosulfate citrate bile salt sucrose medium. The isolate is subcultured to a sheep blood agar plate with an O/ 129 disk. The isolate is sensitive to O/ 129 and is oxidase-positive. You should suspect:

a. Vibrio parahaemolyticus
b. Vibrio cholerae
c. Plesiomonas
d. Aeromonas

Answer 11

b. Vibrio cholerae

Question 12

Which of the following Vibrio spp. would you expect to be most likely isolated from a blood culture?

a. V. cholerae
b. V. parahaemolyticus
c. V. vulnificus
d. V. alginolyticus

Answer 12

c. V. vulnificus

Question 13

Which of the following genera is typically microaerophilic?

a. Helicobacter
b. Aeromonas
c. Plesiomonas
d. Vibrio

Answer 13

a. Helicobacter

Question 14

Campylobacter jejuni is most noted for causing:

a. Wounds
b. Septicemia
c. Gastric ulcers
d. Gastroenteritis

Answer 14

d. Gastroenteritis

Question 15

Which of the following is a risk factor for acquiring V. alginolyticus infection?

a. Farming
b. Hunting
c. Fishing or swimming in ocean water
d. Drinking unpasteurized milk

Answer 15

c. Fishing or swimming in ocean water

Question 16

An oxidase-positive, indole-positive, β-hemolytic, gram-negative bacillus resistant to O/ 129, cannot grow in 6% NaCl broth, and is Voges-Proskauer positive is isolated from an adult stool culture. You should suspect:

a. Aeromonas hydrophila
b. Aeromonas caviae
c. Plesiomonas shigelloides
d. Vibrio parahaemolyticus

Answer 16

a. Aeromonas hydrophila

Question 17

Darting motility is a characteristic of:

a. Aeromonas
b. Campylobacter
c. V. cholerae O1
d. V. cholerae non-O1

Answer 17

b. Campylobacter

Question 18

Which of the following tests is most helpful in differentiating C. jejuni from the other Campylobacter spp.?

a. Nitrate reduction
b. Urease activity
c. Hippurate hydrolysis
d. Susceptibility to nalidixic acid

Answer 18

c. Hippurate hydrolysis

Question 19

When attempting to recover enteric Campylobacter spp., which specimen, media, and incubation conditions should be used?

Answer 19

Appropriate specimens for the isolation of enteric campylobacters are stool samples and rectal swabs; stool samples are preferred. Two categories of media are available for isolation: blood-based and charcoal-based media. A commonly used blood-based medium is CAMPY-BAP. This is a Brucella agar– based medium, with 10% sheep red blood cells and a combination of antimicrobials. Charcoal cefoperazone desoxycholate agar is an alternative. The addition of antimicrobial agents and incubation of the plates at 42 ° C inhibits normal fecal biota. Because the campylobacters require oxygen at a concentration less than room air, they must be incubated in a microaerophilic atmosphere.

Question 20

What nonculture methods are used to diagnose Helicobacter pylori infections?

Answer 20

The most commonly used nonculture method for the diagnosis of H. pylori is the noninvasive 13C- or 14C-labeled urea breath test. The patient receives an oral dose of labeled urea. Urease activity by H. pylori results in the formation of radioactive-labeled CO2, which is absorbed into the bloodstream and then exhaled. Other nonculture methods include microscopic examination of stained gastric tissue, direct fecal antigen detection, polymerase chain reaction assay, and determining urease activity of gastric biopsy material.

Question 21

Points to Remember

Answer 21

■ Most species in this chapter are found in fresh, estuarine, or marine water.
■ Ten species of Vibrio have been implicated in human infection and most are agents of diarrheal disease.
■ V. cholerae produces a powerful enterotoxin and is responsible for large numbers of epidemics and pandemics.
■ Other Vibrio spp. are common causes of diarrheal disease related to the consumption of raw shellfish or related to aquatic wound infections with serious sequelae, such as septicemia and death.
■ Thiosulfate citrate bile salt sucrose (TCBS) agar is the medium of choice to isolate and differentiate the Vibrio spp. This medium distinguishes sucrose-fermenting strains from non– sucrose-fermenting strains.
■ Aeromonas spp. can cause several types of diarrhea and a variety of extraintestinal infections that can lead to septicemia, meningitis, and death.
■ Human Campylobacter spp. are generally responsible for enteritis; C. jejuni is one of the most common causes of bacterial diarrhea worldwide.
■ Patients suffering from Guillain-Barré syndrome (GBS) often test positive for Campylobacter antibodies. GBS is believed to be an autoimmune disorder resulting from cross-reactivity of Campylobacter antibodies with the nerve ganglia.
■ H. pylori is strongly associated with gastric and duodenal ulcers and has been implicated in cases of gastric carcinoma.