The toxigenic Inaba serotype of Vibrio cholerae O1 biotype El Tor reappeared in India in 1998 and 1999, almost 10 years after its last dominance in Calcutta in 1989. Extensive molecular characterization by ribotyping, restriction fragment length polymorphism, and pulsed-field gel electrophoresis indicated that recent Inaba strains are remarkably different from the earlier Inaba strains but are very similar to the prevailing V. choleraeO1 Ogawa El Tor biotype strains. The antibiograms of the Inaba strains were also similar to those of the recent V. cholerae Ogawa strains. These V. cholerae O1 Inaba strains appear to have evolved from the currently prevailing Ogawa strains and are likely to dominate in the coming years.
Vibrio fluvialis is a halophilic Vibrio species associated with acute diarrhoeal illness in humans. It has the potential to cause outbreaks and has an association with paediatric diarrhoea. In this study, 11 V. fluvialis strains isolated from hospitalized patients with acute diarrhoea at the Infectious Diseases Hospital, Kolkata were extensively characterized. All the strains showed growth in peptone broth containing 7 % NaCl. The strains showed variable results in Voges-Proskauer test and to a vibriostatic agent. There was also variation in their antibiograms, and some of the strains were multidrug resistant. Among the 11 strains, two showed only a single band difference in their PFGE profile and the remaining strains showed nine different PFGE patterns. However, unlike PFGE, the strains exhibited close matches and clustering in their ribotype patterns. The haemolytic effect on sheep red blood cells varied with strains. Partial sequence analysis revealed that the V. fluvialis haemolysin gene has 81 % homology with that of the El Tor haemolysin of Vibrio cholerae. A striking finding was the capability of all the strains to evoke distinct cytotoxic and vacuolation effects on HeLa cells. INTRODUCTIONDuring the late 1970s, a previously unidentified group of vibrios was isolated from diarrhoeic stools of infants, children and young adults in Bangladesh (Huq et al., 1980). These vibrios were designated 'group F' vibrios in England (Furniss et al., 1977) and 'CDC group EF6' in the USA (Huq et al., 1980). Taxonomic studies concluded that these organisms represented a new species, and they were designated as Vibrio fluvialis (Lee et al., 1981).The distribution of V. fluvialis is worldwide (McNicol et al., 1980;Thekdi et al., 1982) and this organism is not only isolated from human diarrhoeal cases (Huq et al., 1980;Tacket et al., 1982;Thekdi et al., 1982;Hickman-Brenner et al., 1984;Klontz et al., 1994;Hodge et al., 1995) but also from marine and estuarine environments (Seidler et al., 1980;Lee et al., 1981;Morris & Black, 1985). There are reports of food poisoning caused by this organism (Kobayashi & Ohnaka, 1989;Thekdi et al., 1990), especially due to consumption of raw shellfish (Levine & Griffin, 1993). V. fluvialis is also associated with extraintestinal infections (Yoshii et al., 1987;Albert et al., 1991). The clinical symptoms of the disease include mild to moderate dehydration, vomiting, fever, abdominal pain and diarrhoea (Seidler et al., 1980). The halophilic V. fluvialis (Lee et al., 1981;Lockwood et al., 1982) phenotypically resembles Aeromonas species (Seidler et al., 1980) and taxonomically lies between Aeromonas and Vibrio species (Thekdi et al., 1990). Among the halophilic vibrios, it has close similarity to V. furnissii, but, unlike V. fluvialis, V. furnissii is aerogenic in nature (Brenner et al., 1983).Since V. fluvialis enteritis is reported infrequently, the epidemiology of this infection is not adequately understood. There is very little information available on the virulence factors associated wit...
, teams from the National Institute of Cholera and Enteric Diseases, Calcutta, India, examined eight outbreaks of cholera, which occurred in different parts of the country distant from each other. In two of these outbreaks each, only V. cholerae O1 biotype ElTor or V. cholerae O139 could be isolated, while in the remaining four outbreaks, both O1 and O139 were isolated. The interesting feature is the escalating association of V. cholerae O139 with outbreaks of cholera; two of the most recent outbreaks, one in Calcutta and one in Orissa, were caused exclusively by O139. The O139 strains from the six different outbreaks were genotypically closely related. These trends indicate a shift in the outbreak propensity of V. cholerae O139.Vibrio cholerae O139 Bengal, the new causative strain of cholera, first emerged in September 1992 in the south Indian coastal city of Madras and then spread rapidly to different areas of cholera endemicity in India and its neighboring countries (
Sixteen of the 18 Vibrio cholerae rough strains isolated from hospitalised diarrhoea patients were found to contain O1 serotype-specific (wbe) genes and all currently known virulence genes. Expression of the regulatory element ToxR was evident in these strains. Cholera toxin production ability of the rough strains was found to be higher (c. three-to five-fold) as compared to the smooth counterparts and this was transcriptionally regulated. Strains exhibiting the rough phenotype were more amenable to the uptake of CTXP, which led us to consider that the rough phenotype could play a role in the generation of genetic diversity among V. cholerae strains.
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