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Chapter 16 : Vibrio Species
Category: Applied and Industrial Microbiology; Food Microbiology
A number of reviews on the pathogenic vibrios have appeared over the years, although with the exception of those of Vibrio cholerae and V. parahaemolyticus, relatively little is known of the virulence mechanisms they employ. One of the most consistent features of human vibrio infections is a recent history of seafood consumption. A survey of frozen raw shrimp imported from Mexico, China, and Ecuador found over 63% to harbor Vibrio species, including V. vulnificus and V. parahaemolyticus. By employing sucrose as a differentiating trait, 11 of the 12 human pathogenic vibrios can be separated on thiosulfate-citrate-bile salts-sucrose (TCBS) into 6 species which are generally sucrose positive and 5 species which are generally sucrose negative. With the exception of those of V. cholerae, V. parahaemolyticus, and V. vulnificus, relatively little is known of the susceptibilities of vibrios to various food preservation methods. As with that of other Vibrio species, the reservoir of V. mimicus is the aquatic environment. Indeed, studies from other laboratories using arbitrarily primed polymerase chain reaction (PCR), ribotyping, pulsed-field gel electrophoresis (PFGE), and amplified fragment length polymorphisms all indicate that no two V. vulnificus isolates have the same chromosomal arrangement. In addition to the role of capsule, iron, and endotoxin in the pathogenesis of V. vulnificus infections, V. vulnificus produces a large number of extracellular compounds, including hemolysin, protease, elastase, collagenase, DNase, lipase, phospholipase, mucinase, chondroitin sulfatase, hyaluronidase, and fibrinolysin.
Classic model of cholera toxin mode of action involving cAMP. More recent evidence indicates that prostaglandins and the ENS are also involved in the response to cholera toxin (see the text for details). (A) Adenylate cyclase, located in the basolateral membrane of intestinal epithelial cells, is regulated by G proteins. Cholera toxin binds via the B subunit pentamer (shown as open circles with the A subunit as the inverted solid triangle) to the GM1 ganglioside receptor inserted into the lipid bilayer. (B) The toxin enters the cell via endosomes, and the A1 peptide ADP-ribosylates Gsα located in the basolateral membrane. (C) Increased cAMP activates PKA, leading to protein phosphorylation. In crypt cells, the protein phosphorylation leads to increased Cl− secretion; in villus cells, it leads to decreased NaCl absorption. Adapted from reference 88 .
Correlation between culturability of Vibrio spp. from estuarine environments and water temperature. Reprinted with permission from Pfeffer et al. ( 159 ).
Morphologies of opaque (encapsulated) and translucent (nonencapsulated) colonies of V. vulnificus.
Key differential characteristics of food-associated pathogenic Vibrio species a
Differentiation of the three biogroups of V. vulnificus a