Biology Reference
In-Depth Information
VIBRIO VULNIFICUS
Overview
Vibrio vulnifi cus
is considered the most serious and invasive of all human
pathogenic vibrios in the U.S. accounting for 95% of all seafood-related
deaths in this country (Oliver, 1989). Three biotypes are presently
recognized and distinguished on the basis of biochemical characteristics,
serology, and molecular typing. The organism requires at least 0.5% NaCl
for growth and has been found to be a natural inhabitant of marine coastal
waters and to be globally ubiquitous (Kaysner et al
.
, 1987; Kelly, 1982;
Oliver, 1989; O'Neill et al., 1992; Tamplin et al., 1982).
The most frequent symptoms include fever, chills, nausea, hypotension,
and endotoxic shock which are usually associated with endotoxicity
derived from Gram negative lipopolysaccharides (LPS) (McPherson et al.,
1991). Liver damage or cirrhosis, arising from chronic alcoholism, chronic
renal disease, diabetes, and immunocompromising diseases are considered
major factors in susceptibility (Desenclos et al.,
1991; Oliver, 1989; Johnston
et al., 1986) and are thought to be responsible for the observation that
outbreaks involving the consumption of oysters from a specifi c lot usually
involve only a single susceptible individual developing symptoms (Oliver
and Kaper, 1997). Secondary necrotic lesions of the extremities frequently
occur (69%) often necessitating surgical debridement or limb amputation
(Oliver and Kaper, 1997).
The organism produces an unusually large number of extracellular
virulence factors. A number of selective agar media have been developed
for isolation of the organism incorporating various levels of the antibiotics
such as colistin and polymyxin-B, in addition to bile salts, and K tellurite.
The heat stable hemolysin-cytolysin gene
cth
has been used most frequently
for the specifi c PCR detection and identifi cation of
V. vulnifi cus
.
Virulence Factors
Capsule Production
All virulent strains of
V. vulnifi cus
were found by Simpson et al
.
(1987) to
produce opaque colonies derived from encapsulated cells whereas non-
encapsulated spontaneous mutants of the same strains were found to
produce translucent (non-capsular) colonies that were avirulent.
Extra-cellular Virulence Factors
V. vulnifi cus
produces a large number of extracellular factors that are
considered to contribute to its virulence including: collagenase (Poole
et al
.
, 1982; Smith and Merkel, 1982; Oliver et al., 1986), hemolysins
(Moreno and Landgraf, 1998), proteases (Desmond et al., 1984; Kreger
