Plasmid-determined degradative metabolism and halophilism of Vibrio parahaemolyticus

A set of 25 Kanagawa(+) and Kanagawa(-) strains of V. parahaemolyticus was studied for their ability to degrade hydrocarbons in minimal media. All strains gave positive results with respect to crystal violet (CV), methyl violet, liquid paraffin, benzene, naphthalene and phenol. The CV double ring (CVDR) response had earlier appeared to be a significant pathogenic marker [Chakrabarti et al, Indian J Med Res, 85 (1987) 508]. The CVDR response was found also to be a biodegradative marker, and correlates perfectly well with polymyxin resistance and low level of halophilism (4% NaCl). All these markers (characters) were found to be controlled by a single plasmid in the wild type. Elimination of the plasmid, as confirmed by gel electrophoresis studies, resulted in loss of CVDR response, polymyxin resistance, and acquisition of halophilism at a higher level (> 7%). The massive drainage of industrial effluents, rich in hydrocarbons, in the estuarine areas in many countries might have altered the ecosystem in favour of V. parahaemolyticus and its emergence as a new biodegradative and enterotoxigenic pathogen, contaminating fauna and flora in the littoral sea regions, with increased changes of communicability to humans.