Vibrio

On exam #5, this is on the last exam of the semester. Focuses on Vibrio organism

what is the description of the genus vibrio?

short, curved, rod-shaped organisms

what family are vibrio closely related to?

Enterobacteriaceae

how are vibrio motile?

they have a single flagellum

what are the antigens found on the vibrio? which one is useful to distinguish strains?

O and H antigens are both present but the O antigen is used to distinguish strains of vibrios that cause epidemics

In what conditions does the vibrio species thrive in?

they are facultative anaerobes(fermentation & aerobic respiration) and many require or is stimulated by NaCl

what are the three pathogenic vibrios?

1. V.cholerae, serogroup O1 strain: associated with epidemic cholera

2. non-O1 V.cholerae: cause sporadic cases of cholera life and other illnesses

3. V.parahaemolyticus and other halophilic vibrios: cause gastroenteritis and extraintestinal infections

How is v.cholera transmitted?

contaminated water and food

what are the two biotypes of the V.cholerae serogroup O1 species?

1. Classic:

2. El Tor: strain is distinguished from the classic strain by the production of hemolysins, higher carriage rates, and the ability to survive in the water for longer period.

Once cholerae has been ingested how does it stay in the human body?

attaches to the cells lining the small intestinal villi and secrete the AB type choler toxin

is v.cholerae invasive or noninvasive?

noninvasive, causes disease through the action of an enterotoxin that initiates an outpouring of fluid

what are the subunits that cholera toxin is made out of? describe each subunit

cholera toxin is composed of an A and a B subunit

a. B subunit binds to the GM1 ganglioside receptor of cells lining the intestine

b. A subunit has two components: A1 and A2

what is cAMP?

formed from cytosolic ATP by adenylyl cyclase and serves as a secondary messenger in cellular signaling.

how does the G protein in vibrio become activated?

the enzyme become activated when bound to activated G alpha released from G beta and gamma and GTP bound. when GTP is hydrolyzed GDP alpha is released and adenylyl cyclase becomes inactivate

In order to understand how cholera toxin affects adenylate cyclase regulation in humans, you must understand the normal regulation of adenylate cyclase (explain)

Cyclic AMP (cAMP) is formed from cytosolic ATP by adenylyl cyclase, an enzyme that is anchored in the plasma membrane.

- The enzyme becomes active when bound to activated Gα (released from Gβγ and GTP-bound).

- When GTP is hydrolyzed, GDP-Gα is released and adenylyl cyclase becomes inactive

How does the cholera toxin impact the regulation of cyclase?

1. the 5B:1A CT toxin complex binds to ganglioside GM1 on host membrane lipid rafts

2. the toxin is endocytosed

3. the phagosome containing CT is taken into the ER

4. the A1 subunit is removed form the B subunits and exported into the cytoplasm

5. A1 attaches an ADP ribose to the host Gs protein that keeps adenylate cyclase activity but loses GTPase activity

6. cAMP levels rise and activate ion transport system, causing electrolyte imbalance. Water from the cell follows the ions, causing diarrhea.

how long is the period of incubation for cholera?

hours to a few days

what happens if cholera is left untreated?

death from severe dehydration causing hypovolemic shock (decreased volume of circulating blood) in hours to days

How to identify vibrio in lab?

grows on standard medium such as MacConkey. Thiosulfate citrate bile salts sucrose medium to enhance isolation

oxidase + (further biochemical tests required)

what is the treatment/prevention for cholera?

fluids, electrolytes (via intravenous rehydration)

prevention by reducing fecal contamination of water supplies and food.

what is different about vibrio parahaemolyticus and other halophilic, non cholera vibrios?

usually require high concentrations of NaCl (10%), common in costal sea water.

vibriosis

is one of the major disease problems in shellfish, finfish, and crustaceans.