The purpose of this study to assess the in vitro susceptability of 50 Edwardsiella ictaluri isolates originated from Vietnamase freshwater catfish (Pangasianodon hypophhalmus) caused Bacillus Necrosis Pangasius (BNP) in the commercial...
moreThe purpose of this study to assess the in vitro susceptability of 50 Edwardsiella ictaluri isolates originated from Vietnamase freshwater catfish (Pangasianodon hypophhalmus) caused Bacillus Necrosis Pangasius (BNP) in the commercial catfish farms in the Mekong Delta from 2007 to 2009. All isolates were screened against 17 antimicrobial agent by disk diffusion method and were also tested for determination of minimal inhibitory concentration (MIC) to 4 antibiotics with method with broth dilution. The results show that none of isolates displayed resistant ability to cefotaxime, nitrofurazole. Majority of antimicrobial agents displayed indicating reduced susceptibility of a minority of isolates, namely cefazoline (2% of the total resistant strain), cefalexin (2%), neomycin (6%), amoxicillin + clavulanic acid (8%) và ampiciline (14%). Whereas, all isolates showed resistance to flumenquin, trimethoprim + sulfamethoxazol. Highly resistance was detected to enrofloxacin (93%), chloramphenicol (82%), streptomycin (80%). The results of MIC value were hightly in most of tested isolates. The aquired resistance were found streptomycin with an MIC 90 ≥256µg/ml, chloramphenicol, enrofloxacin with an MIC 90 128µg/ml, oxytetracyline (64µg/ml). Remarkably, multiresistance of E.ictaluri isolates were 86 % of the total resistant isolates to at least three antimicrobials. This results indicated the necessity for further research on resistant mechanism of pathogens and the transfer of antimicrobial resistant genes among environmental microflora in the intensive catfish farms in the Mekong Delta.