Studies on the bacterial flora of fish which are potential pathogens for human. Virulence factors of potential human pathogen isolated.

Tests for various virulence factors, such as production of haemolysin on sheep blood agar plate, cytotoxin on HeLa cell line and enterotoxin in GM-1 ELISA and suckling mouse assay model, were done among the various strains of Aeromonas spp., Vibrio spp., Plesiomonas shigelloides and Esch. coli isolated from fresh water fish samples. Invasive properties of the isolates were also seen by using Sereny test. Haemolysin production was observed in 85.7% of Aeromonas, all (100%) of Vibrios, 13.3% of Esch. coli and none (0%) of P. shigelloides strains. Cytotoxin production was demonstrated in 60.8% of Aeromonas, 38.4% of Vibrios and none (0%) of P. shigelloides and Esch. coli strains. About 8% of Vibrio spp., were found positive for LT in GM-1 ELISA method whereas, none of the Aeromonas spp., Plesiomonas and Esch. coli. strains were found positive for LT and ST in GM-1 ELISA. By suckling mouse assay model 43.4% strains of Aeromonas were found positive for enterotoxin production whereas, strains of Vibrio spp., Plesiomonas and Esch. coli yielded negative results. Sereny test for invasive property was found negative in all the strains tested. The isolates from fish possess various virulence factors which contributes for pathogenicity in order to cause various diseases to susceptible individual.