Microbes 9-13, GNB

Question 1

Vibrio cholerae, morphology?

Answer 1

a. Gram-negative bacillus, curved

b. Most pathogens are antigenic groups O1 or O139

Question 2

etiologic agent? enterocolitis syndrome (gastroenteritis)

Answer 2

Vibrio Cholerae

Question 3

(a) Endemic to areas with poor sanitation e.g. tropical Asia (especially India), Africa,
parts of S. & C. America – several hundred thousand cases per year

(b) Usual transmission of epidemic cholera is through ingestion of contaminated water
drinking, food preparation, bathing

Answer 3

Vibrio cholerae

Question 4

Vibrio cholerae, cholera ingested in #s?
incubation period?
localized where?

Answer 4

(a) Organisms ingested in large numbers
(b) Incubation period – few hours to five days
(c) Non-invasive organisms localize in small intestine

Question 5

Enterotoxic exotoxin:
i. Stimulates hypersecretion of water and chloride
ii. Reverses ion transport in gut (alters intestinal permeability)
iii. Causes massive diarrhea – “rice water stools” – up to 16 liters a day – severe
dehydration

Answer 5

Vibrio Cholerae

Question 6

Vibrio cholerae, cholera mortality rate if untreated?

Answer 6

up to 50%

Question 7

(a) General control by good hygiene and disinfection of items contaminated with feces
and vomitus
(b) Oral replacement of fluid using electrolyte solution with glucose or sucrose
(c) Intravenous infusion of balanced multi-electrolyte solution
(d) Antibiotics – Tetracycline and other broad spectrum antibiotics are effective in a
short time. Use typically limited to the severely compromised patients.
(e) Immunization is ineffective and not recommended by WHO

Answer 7

treatment for Vibrio cholerae

Question 8

Vibrio cholerae, Laboratory diagnosis?

Answer 8

Special request for culture needed in the USA due to rarity and need
for special media (alkaline and selective)

Question 9

Etiologic agent of a gastroenteritis due to the ingestion of contaminated
shellfish (especially oysters) –a common cause of gastroenteritis in Asian coastal regions, lower
frequency in US.

Answer 9

Vibrio Parahemolyticus

Question 10

Vibrio vulnificus, found where?

Answer 10

Found in warm, coastal seawater

Question 11

infrequent, acute infection (fewer than 100 cases per year, but probably
underreported)

(1) Acute gastroenteritis and primary septicemia due to ingestion of raw or undercooked
seafood, particularly raw oysters. (very high fatality rate ~50%)

(2) Severe cellulitis due to seawater contaminating a break in the skin – causes severe
skin/tissue infection with hemorrhagic bullae and necrotizing fasciitis. (high fatality rate
~15%)

Answer 11

Vibrio Vulnificus

Question 12

Gram-negative bacillus, thin curved rods, occasional ‘s’ or gull wing shapes

Answer 12

Campylobacter Jejuni

Question 13

Campylobacter jejuni, transmission and epidemiology, incubation period?

Answer 13

(1) Generally originates from ingestion of fecal contaminated food, especially under cooked
chicken or contamination of other foods from uncooked chicken, raw milk (from cattle
feces), and non-chlorinated water

(2) Incubation period: 2-5 days; symptoms usually resolve in 3-6 days

Question 14

gastroenteritis (enterocolitis syndrome) – prevalence # 1 or 2 in North America (similar to Salmonella)

Ulceration of intestinal mucosal epithelium causing diarrhea (infrequently bloody stools),
abdominal pain, nausea, vomiting, (infrequent fever)

Answer 14

Campylobacter Jejuni

Question 15

(a) Grows in human bile
(b) Flagella promote chemotaxis to colonize the intestine
(c) Adhesive molecules promote attachment
(d) Production of Cytolethal Distending Toxin (CDT) – AB-type toxin that has DNase
activity (directly damages DNA)

Answer 15

Campylobacter Jejuni

Question 16

Campylobacter jejuni, treatment and control?

Answer 16

• Generally no antibiotic treatment, only rehydration and electrolyte
  replacement. [Erythromycin and tetracyclines are used to eliminate carrier state or in severely
  compromised patient.]

Question 17

Campylobacter jejuni, laboratory diagnosis? incubation period?

Answer 17

Special culture media and environmental conditions needed for
culture and biochemical identification

(1) Selective culture media with antibiotics
(2) Microaerophile – Transport & incubate in reduced oxygen (about 5%) & increased CO2

(3) Incubation of primary isolation media at 42°C permits differentiation of certain species
from those that can grow only at 37C

Question 18

Helicobacter pylori morphology?

Answer 18

Curved gram-negative bacillus

Question 19

Helicobacter pylori, etiologic agent of?

Answer 19

peptic ulcers – causes chronic inflammatory lesions of the gastric mucus layer.

Question 20

Helicobacter pylori, diagnostic testing?

Answer 20

(1) Breath test to detect urease production
(2) Endoscopy and biopsy – Culture requires microaerophilic environment and special
growth media; DNA probe