Abstract
Transmission of extended-spectrum β-lactamase (ESBL) genes has increased the global prevalence of ESBL-producing bacteria, especially in developing countries. Human infection with these bacteria may be food-mediated but has not been fully elucidated. Therefore, we aimed to examine ESBL-producing bacteria in edible river fish and elucidate their potential for horizontal gene transfer. A total of 173 ESBL-producing Enterobacterales were isolated (Escherichia coli [n = 87], Klebsiella pneumoniae [n = 52], Enterobacter cloacae complex [n = 18], Citrobacter freundii complex [n = 14], Atlantibacter hermannii [n = 1] and Serratia fonticola [n = 1]) from 56 of 80 fish intestinal contents sampled. Among the bacterial bla (CTX-M) genotypes, bla (CTX-M-55) was the most predominant, followed by bla (CTX-M-15), bla (CTX-M-27), and bla (CTX-M-65). Furthermore, we found that ESBL-producing Enterobacterales were able to transfer their bla (CTX-M) genes to E. coli. In summary, our results suggest that ESBL-producing Enterobacterales transfer bla (CTX-M) to indigenous gut E. coli in humans, following the consumption of contaminated fish.