Cholera Flashcards
(26 cards)
What are Vibrios?
Curved gram-negative bacilli that are actively motile by means of a single polar flagellum.
Who isolated the organism Vibrios and when?
Robert Koch in 1886.
What is the natural habitat of Vibrios?
Marine environments, surface waters, river, and sewage.
What disease does V. cholerae cause?
Cholera.
How many global pandemics has V. cholerae been responsible for?
Seven global pandemics.
What are the two classifications of Vibrios based on salt requirement?
- Nonhalophilic vibrios
- Halophilic vibrios
What defines nonhalophilic vibrios?
They can grow without salt, but 1% salt is optimum for their growth.
What defines halophilic vibrios?
They cannot grow in the absence of salt and tolerate higher salt concentrations of up to 7-10%.
What is the Gardner and Venkatraman classification based on?
Serogrouping, biotyping, serotyping, and phage typing.
What is serogrouping?
Grouping based on somatic O antigen; V. cholerae can be grouped into more than 200 serogroups.
What is the significance of the 01 serogroup?
Responsible for all pandemics and most epidemics of cholera.
What are NAG vibrios?
Serogroups other than O1 that were thought to be non-pathogenic.
What is the 0139 serogroup known for?
Identified in 1992 and has caused several epidemics of cholera.
What are the two biotypes of serogroup O1?
- Classical
- El Tor
What is the infective dose of V. cholerae?
A high infective dose of 10^8 bacilli is required.
What is the primary mode of transmission for V. cholerae?
Ingestion of contaminated water or food.
What factors promote the transmission of cholera?
- Conditions reducing gastric acidity
- Use of antacids
What is the role of cholera toxin (CT) in cholera pathogenesis?
It causes the watery diarrhea associated with cholera.
What are the two fragments of the cholera toxin molecule?
- Fragment A
- Fragment B
What is the function of Fragment B of cholera toxin?
It binds to GM1 ganglioside receptors on intestinal epithelium.
What does Fragment A of cholera toxin do?
Causes ADP ribosylation of G protein, upregulating adenylate cyclase activity.
What leads to the accumulation of isotonic fluid in the intestinal lumen?
Increased cyclic AMP inhibits sodium absorption and activates chloride secretion.
What are the three serotypes of serogroup O1?
- Inaba
- Ogawa
- Hikojima
What is the significance of the El Tor biotype?
Replaced the classical biotype by 1961 and caused the seventh pandemic.
