Characterization of antibiotic resistance in Escherichia coli isolated from shrimps and their environment.

Antimicrobial resistance in bacteria associated with food and water is a global concern. To survey the risk, 312 Escherichia coli isolates from shrimp farms and markets in Thailand were examined for susceptibility to 10 antimicrobials. The results showed that 17.6% of isolates (55 of 312) were resistant to at least one of the tested drugs, and high resistance rates were observed to tetracycline (14.4%; 45 of 312), ampicillin (8.0%; 25 of 312), and trimethroprim (6.7%; 21 of 312); 29.1% (16 of 55) were multidrug resistant. PCR assay of the tet(A), tet(B), tet(C), tet(D), tet(E), and tet(G) genes detected one or more of these genes in 47 of the 55 resistant isolates. Among these genes, tet(A) (69.1%; 38 of 55) was the most common followed by tet(B) (56.4%; 31 of 55) and tet(C) (3.6%; 2 of 55). The resistant isolates were further investigated for class 1 integrons. Of the 55 resistant isolates, 16 carried class 1 integrons and 7 carried gene cassettes encoding trimethoprim resistance (dfrA12 or dfrA17) and a...