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BACTERIOLOGY
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MicroBioNet
Your Microbiology Universe on the Internet
| Vibrio cholerae |
| CLASSIFICATION | VIRULENCE FACTORS | ENVIRONMENTAL |
| BIOCHEMISTRY | NORMAL FLORA | INDUSTRIAL USES |
| GENETICS | PATHOGENS | VACCINES |
| SEROLOGY | LABORATORY ID |
The classification is based chemotaxonomic criteria. These are based on DNA-DNA homology studies. These agree with with those based on protein structure. More recent RNA sequence data disagree with some of these points and there may have to be a reevaluation.
Vibrio cholerae is not pigmented. In many instances metabolic acivity is enhanced by the presence of 1% NaCl. Acid is produced from glucose and frequently acetoin (Voges-Proskauer positive). They produce indole, decarboxylate lysine and ornithine. They do not produce arginine dihydrolase and rarely hydrolyse aesculin. They reduce nitrate to nitrite.
Serogrouping is based
on the somatic (O) antigen. There are well over 100 O groups known of which
until recently only strains of O1 group were considered consistantly as enteric
pathogens causing cholera. O1 strains can be subtypes on the basis of subfactors
into types Ogawa, Inaba and Hikojima.
Recently there emerged
strains of serogroup O139 with similar properties.
Antisera to flagellar
antigens can also be used to subtype strains.
Cholera toxin (Choleragen)
with a molecular weight of 84,000 is considered to be predominantly associated
with cholera. The enzymic acitivity of choleragen causes the activation
of host adenylate cyclase increasing cyclic AMP levels. This causes excessive
secretion of salts and water leading severe diarrhoea followed by dehydration.
Some strains produce
a haemolysin.
Some non-O1 strain
produce a heat-stable enterotoxin. They may also produce other toxins causing
gastroenteritis.
Serogroup O1 strains are rarely found outside the human intestinal tract generally in association with disease. They can be occasionally isolated from the environment but these are often not toxigenic. Non-O1 strains can be isolated from rivers, particularly in warmer climates.
Intestinal Infections:
O1 and O139 strains are
the causes of severe cholera. Other serogroups have been associated with cases
severe dehydrating gastroenteritis. Some cases are associated with diarrhoea
and fever with faecal blood and/or mucus.
Strains of V. cholerae can be isolated from faecal specimens on many of the media used for Enterobacteriaceae. Direct agglutination assays on liquid stools can be used for the rapid screening for O1 strains, but these will not pick out the O139 strains. Sucrose fermenting (Yellow) colonies on Thiosulphate-Citrate-Bile Salts-Sucrose (TCBS) agar are characteristic for V. cholerae.
Can be found in water as well as environments in association with humans, particularly in warmer climates.
None.
Oral choleragen toxoid can be given to prevent to development of cholera to travellers or during epidemics.
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GRAM
NEGATIVE
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FAMILIES
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| Acetobacteriaceae |
| Alcaligenaceae |
| Bacteroidaceae |
| Chromatiaceae |
| Enterobacteriaceae |
| Legionellaceae |
| Neisseriaceae |
| Nitrobacteriaceae |
| Pseudomonadaceae |
| Rhizobiaceae |
| Rickettsiaceae |
| Spirochaetaceae |
| Vibrionaceae |
| Genera of Unestablished Relationships |
| Brucella |
| Chromobacterium |
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