Curved, Gram-Negative Bacilli Flashcards
General characteristics of Vibrio species
- Gram-negative curved or comma-shaped bacilli.
- Motile (polar, monotrichous flagellum), EXCEPT Vibrio metschnikovii; they exhibit “darting: or “shooting star” motility
- Non-spore-forming
- Facultative anaerobic
- Aquatic organisms that are found in fresh water, brackish or estuarine water, and marine or salt water
- Grow in alkaline media
- Most are halotolerant, some are halophilic
- Glucose fermentation
- Catalase(+), EXCEPT Vibrio metschnikovii
- Oxidase(+), EXCEPT Vibrio metschnikovii
What is the common name of V. cholerae ?
Komabacillus
Habitat of V. cholerae
Human colon
Can survive and grow in brackish water
What is the infectious dose of V. cholerae and why ?
They are sensitive to gastric acid hence high dose is required, 10^10 organisms per mL
Transmission of V. cholerae
Fecal-oral route, contaminated waters
Eating raw shellfish from contaminated waters
What are other names of cholera ?
Asiatic cholera or epidemic cholera
What is the incubation period of cholera ?
12 hours up to 3 days depending on the size of the inoculum ingested
Symptoms of cholera
sudden onset:
nausea
vomiting
abdominal cramps
profuse “rice water” diarrhea (stool resembles water in which the rice has been boiled) that may be as many as 10 to 30 per day
containing mucus, epithelial cells, and large numbers of vibrios
What can happen if cholera is left untreated ?
a rapid fluid and electrolyte loss that leads to: dehydration hypovolemic shock metabolic acidosis death in a matter of hours.
How does motility and mucinase assist V. cholerae in causing disease ?
aid in the penetration of the protective mucin layer that coats the surface of the gastroenteric mucosa
Characteristics of choleragen
cholera toxin is a heat-labile enterotoxin
the genes for which are encoded in a lysogenic phage consists of 2 subunits: A (active) subunits and binding (B) subunits
Differentiate the two peptides comprised of the A subunit of choleragens
A1 persists toxin activity, activates adenylate cyclase; hypersecretion of electrolytes (Na+, K+, HCO3−) and water out of the cell
A2, which facilitates penetration of the A1 subunit into the enterocyte
What is the structure of a choleragen ?
There are five B subunits per toxin molecule, arranged in a ring around a central core that contains the enzyme A1
What is the role of the B subunit of choleragens ?
B subunit binds the A2 subunit to the GM1 ganglioside receptor on the cell membrane of the enterocytes
Which antigenic structure forms the basis of a serotyping scheme that classifies the 139 strains of V. cholerae, designated from O1 to O139 ?
O antigen
