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22 (2008) analyzed the genetic relatedness and geographical distribution of V. parahaemolyticus from the environment and clinical strains using seven house keeping genes (dnE, gyrB, recA, dtdA, pntA, pyrC, tnaA). 2.7.5 Molecular and genetic characteristics of environmental Vibrio Vibrio species are widely distributed in the aquatic environment and are considered as autochthonous bacteria in the estuarine and marine waters (Nishibuchi and Kaper, 1995). Scientists isolated and identified this organism in the marine water (Faruque et al., 2004, Nair et al., 1988), shrimp and oysters (Dalsgaard et al., 1995 a, Gopal et al., 2005, Sobrinho et al., 2010), sediments (Bhaskar and Setty, 1994), plankton (Lipp and Rose, 1997), and also from the seafood (Chitov et al., 2009 b, Sujeewa et al., 2009). Many investigations were carried out to identify genetic and phenotypic differences between clinical and environmental vibrios. V. cholerae serogroups O1 and O139 caused the epidemics of cholera. But other non O1 and non O139 serogroups can cause sporadic diarrhoea. Environmental strains mainly belong to V. cholerae serogroup non O1 and non O 139 (Faruque et al., 2004). Clinical strains carry the virulence factors for cholera toxin (CT) and toxin- coregulated pilus (TCP) which is central to the disease process and provide adhesion for the toxins respectively (Chakraborty et al., 2000). Studies found that environmental strains of V. cholerae rarely carried CT and TCP. Water samples from two major rivers of Bangladesh were investigated for the presence of V. cholerae and their virulence associated genes. V. cholerae non O1 and non O139 was found in 89.9% (116/125) and 3.2% (4/125) were V. cholerae O1 (Faruque et al., 2004). These authors found one V. cholerae O1 carrying the TCP and CT gene (0.8%) in those environmental samples. Nair et al. (1988) carried out an investigation on V. cholerae non O1 from environmental sources in India, to describe toxin profile. They examined for the production of CT, shiga-like toxin (vero toxin), heat stable enterotoxin and haemolysins. Two of the strains (0.5%) produced CT; none of them produced shiga- like toxin or heat stable enterotoxins. Haemolytic activity was observed in 89.7% of the strains. The authors concluded that only a small percentage of environmental V. cholerae non O1 has the ability of causing cholera like symptoms (Nair et al., 1988).
23 Clinical strains of V. parahaemolyticus have the ability to produce thermostable direct haemolysin (TDH) and TDH related haemolysin (TRH) and can cause gastroenteritis in humans (Su and Liu, 2007, Vongxay et al., 2006). Most of the tdh positive strains of V. parahaemolyticus exhibit the Kanagawa phenomenon, an enzymatic lysis of red blood cells on Wagatsuma blood agar plates (Su and Liu, 2007, Vongxay et al., 2008). Several investigations found that only 1-3% of the environmental strains of V. parahaemolyticus exhibit the toxic activity (Lee et al., 2008a, Vongxay et al., 2006, Sobrinho et al., 2010), (Table 8). But recent reports on the presence of virulence genes in environmental strains of V. parahaemolyticus found an increasing percentage of tdh and trh gene-carrying strains (Deepanjali et al., 2005, Raghunath et al., 2008, Sujeewa et al., 2009, Zimmerman et al., 2007) (Table 8). Those studies showed that, trh-bearing V. parahaemolyticus are more frequently distributed in tropical seafood than tdh-bearing V. parahaemolyticus. V. vulnificus is an opportunistic human pathogen (Cañigral et al., 2009) and unlike V. parahaemolyticus and V. cholerae, environmental and clinical strains of V. vulnificus showed no difference in the potential to produce toxins. Human V. vulnificus infections shows clinical signs of wound infection, fever, chills, hypotension, bulbous like skin lesions which are rapidly progressive and 50% mortality in septicaemia conditions. The polysaccharide capsule and the production of siderphores by this organism are considered as virulence factors (Starks et al., 2000). Tison and Kell (1986) studied the virulence of V. vulnificus isolated from the marine environment. These authors found no difference in their production of virulence factors, both in vitro (cytolysin and cytotoxin) and in vivo (mouse pathogenicity) among clinical and environmental isolates of V. vulnificus. Similar to this study, Wong et al. (2005) also found that environmental strains of V. vulnificus exhibit a similar virulence to clinical strains in mice. These data were supported by Stelma et al. (1992).
Page 1 and 2: 2.1 Shellfish culture CHAPTER II LI
Page 3 and 4: 7 constant over the years while cul
Page 5 and 6: 9 Pathogenic bacteria associated wi
Page 7 and 8: 11 Listeriosis, and other pathogens
Page 9 and 10: Coastal water Shrimp Bangladesh (Co
Page 11 and 12: Table 4: Cholera pandemics Pandemic
Page 13 and 14: 17 parahaemolyticus should be Kanag
Page 15 and 16: 19 2.7.2 Biochemical characteristic
Page 17: 21 2.7.4 Genotypic characteristics
Page 21 and 22: 2.8 Human pathogenic Vibrio 2.8.1 V
Page 23 and 24: 27 Vibrio spp. display similar bioc
Page 25 and 26: 29 host and effluent from the conta
Page 27 and 28: 31 elimination of Edwardsiella tard
Page 29 and 30: A. Cooling and freezing 33 Rapid an
Page 31: 2.10.3 Consumer education 35 Consum

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