Spread of Antibiotic and Antimicrobial Susceptibility of ESBL-Producing Escherichia coli Isolated from Wild and Cultured Fish in the Mekong Delta, Vietnam

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli were isolated from wild and cultured fish (18 striped catfish, Pangasianodon hypophthalmus, and 18 red tilapia, Oreochromis sp.) in the Mekong Delta, Vietnam, from June 2014 to October 2014. In total, 39% of the fish harbored ESBL-producing E. coli, including 44.4% of wild fish and 36.1% of cultured fish. The E. coli isolates were highly resistant to ampicillin, cefotaxime, trimethoprim-sulfamethoxazole, and nalidixic acid among the antibiotics tested. Cephalexin (4/16, 25%), cefazolin (1/16, 6%), enrofloxacin (1/16, 6%), sulfadimidine (3/16, 19%), and sulfamethoxazole (15/16, 94%) were detected in water samples obtained at the fish collection sites. These results showed that the sampled fish harbored ESBL-producing E. coli, suggesting that fish are a potential source of human pathogens and mediate interspecific transfer of antimicrobial-resistant genes.