Tilapia fishes (Oreochromis niloticus) are commonly consumed and exported in Thailand. Bacterial isolation and drug resistance from farmed tilapia fished in Thailand was previously reported. This study was purposed to study on distribution of human pathogenic bacteria in tilapia fishes, which collected from Thai farms (n = 180) and fresh markets (n = 160) by identification, antibiotic susceptibility test; and conduct to identify virulence genes by molecular technique. Pathogen isolations were collected from internal organs of fish samples for identification and test of antibiotic susceptibility according by Clinical and laboratory standards institute (CLSI) criteria. blaCTX-M and Int1genes detection of antibiotic resistance bacteria was performed by molecular based techniques. K. pneumoniae, Edwardsiella tarda and coagulase negative Staphylococci were most frequently bacteria isolated from farming tilapia fishes, respectively. However, E. coli, coagulase negative Staphylococci and K. pneumonia were frequent distributed from tilapia fishes in markets of Bangkok area. K. pneumoniae, E. coli and Proteus mirabilis were resisted to penicillin and ampicillin. K. pneumoniae is most important isolated bacteria, due to the distribution in tilapia fishes and positive for blaCTX-M and Int1gene detection. However, E. coli and P. mirabilis were lack of blaCTX-M and Int1genes, possibly there may reserve other antibiotic resistance genes.
Key words: beta-lactamases, blaCTX-M gene, Int1 gene, Klebsiella pneumoniae, Oreochromis niloticus, Tilapia fish
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