Molecular detection of florfenicol and chloramphenicol resistance among Escherichia coli isolates from healthy pigs during 2003 to 2007

Abstract

In order to elucidate the possible genetic determinants of resistance to florfenicol and chloramphenicol in porcine Escherichia coli in Taiwan, 600 fecal samples of healthy pigs from 50 different farms were collected from 2003 to 2007. The florfenicol resistance in the isolated E. coli strains doubled from 39.2% in 2003 to 78.3% in 2007. A total of 351 florfenicol-resistant E. coli isolates were isolated from nursery pigs (61.5%), grower-finisher pigs (62.5%), and sows (51.5%). The prevalence of resistance genes, floR, cmlA, cat-1, cat-2 and cat-3, was 82.9, 61.3, 10.8, 3.7, and 0%, respectively. Of the 351 florfenicol-resistant isolates, 184 (52.4%) were positive for both floR and cmlA. Furthermore, the results of efflux inhibitor studies with Phe-Arg-β-naphthylamide showed a 4- to 64-fold decrease in the florfenicol MIC levels. The FloR efflux pump may play a role in phenicol resistance among porcine E. coli isolates in Taiwan. More detailed studies are required to focus on the public health concerns about the spread of antimicrobial resistance from animal food products to humans through the food chain.