Chapter 17

Question 1

Where are vibrios found?

Answer 1

Vibrios are among the most common bacteria in marine and estuarine waters, worldwide.

Question 2

Describe vibrios

Answer 2

gram (-); comma-shaped, curved, facultatively anaerobic, fermentative rods; catalase and oxidase positive; most species are motile by means of monotrichous/multitrichous polar flagella; grow within a broad temperature range (14–40°C); halophilic.

Question 3

Pathogenic vibrios:

Answer 3

Vibrio cholera, Vibrio parahaemolyticus, Vibrio vulnificus.

Question 4

Typical organisms of V cholera:

Answer 4

gram (-); comma-shaped, curved rod 2-4μm long; motile with polar flagellum; prolonged cultivation may resemble other gram(-) enteric bacteria

Question 5

Culture of V cholera:

Answer 5

convex, smooth, round; opaque and granular in transmitted light; grows well on 37°C; grows on selective TCBS agar; yellow colonies (sucrose fermenting);

Question 6

What color colonies do V. parahaemolyticus and V. vulnificus produce on TCBS agar?

Answer 6

green colonies

Question 7

Optimal pH for V. cholera:

Answer 7

very high pH (8.5-9.5); they are rapidly killed by acid

Question 8

How are V. cholera specimen collected?

Answer 8

for optimal recovery, specimens should be collected early in the course of the diarrheal illness and inoculated onto agar; if this process is delayed, specimen should be mixed with Cary-Blari medium and refrigerated.

Question 9

Growth characteristics of V. cholera:

Answer 9

oxidase (+); ferments sucrose and mannose, doesn’t ferment arabinose; halophilic, need presence of NaCl for growth;

Question 10

How many serogroupd of V. cholera are there?

Answer 10

over 200; determined by O lipopolysaccharide

Question 11

Which serogroups of V. cholera are epidemic?

Answer 11

V. cholera serogroup O1 and O139

Question 12

Serotypes of V. cholera O1:

Answer 12

Ogawa, Inaba, Hikojima

Question 13

Biotypes of V. cholera O1:

Answer 13

classic and E1 Tor

Question 14

V. cholera E1 Tor is:

Answer 14

hemolysisn (+); positive results on Voges-Proskauer test, resistant to polymyxin B

Question 15

Vibrio cholera enterotoxin:

Answer 15

heat-liable; subunits A and B; GM1 receptor for subunit B, prompts entry of subunit A; increases intacellular cAMP levels, resulting in hypersecretion of water and electrolytes

Question 16

The infectious dose of V. cholera in healthy persons:

Answer 16

10^10 or more V. cholera

Question 17

Which persons are more suceptible to V. cholera infections?

Answer 17

In a persons with achlorhydria or hypochlorhydria; taking medication (PPIs) or conditions that reduce the acidity of the stomach

Question 18

True or false: V. cholera infects the bloodstream.

Answer 18

False, V. cholera is a noninvasive mucosal pathogen; it doesn’t reach the bloodstream and remains in the GI tract.

Question 19

Incubation period of V. cholera is:

Answer 19

12 hours to 3 days after ingestion.

Question 20

Symptoms of V. cholera infection:

Answer 20

sudden onset nausea, vomiting, followed by profuse diarrhea w/ abdominal cramps; stool resembles “rice water”

Question 21

What is present in the stool of a person with V. cholera infection?

Answer 21

resembles “rice water” and contains mucus, epithelial cells, and large number of vibrios.

Question 22

The rate of the fluid loss in V. cholera infection:

Answer 22

1L/hour

Question 23

What does rapid loss of fluid lead to in patients with V. cholera infection?

Answer 23

profound dehydration, painful muscle spasms, metabolic acidosis, hypokalemia, and hypovolemic shock with circulatory collapse, and anuria with associated renal failure.

Question 24

Which type of microscope is used to observe Vibrio cholera?

Answer 24

Dark-field microscopy and phase-contrast microscopy

Question 25

What is the motility type in V. cholera O1?

Answer 25

“Shooting star” motility; used to detect these organism; by addition of O1 antiserum the movement stops

Question 26

What provides the immunity to V. cholera infection?

Answer 26

gastric acid is the main source of immunity to V. cholera; presence of antitoxin antibodies has not been associated with protection; in experimental animals presence of IgA antibodies have been described.

Question 27

Which drugs are used against V. cholera?

Answer 27

Tetracycline; Erythromycin and azithromycin (children, pregnant women); trimethoprim-sulfamethoxazole, fluoroquinolones, and doxycycline.