Characterization of TEM-, SHV- and AmpC-type β-lactamases from cephalosporin-resistant Enterobacteriaceae isolated from swine

Extended-spectrum β-lactamase (ESBL) and AmpC-producing Enterobacteriaceae are an increasing problem in human medicine and an emerging problem in the veterinary field. Our study, therefore, focused on assessing the prevalence of β-lactamases isolated from swine. Sixty-six Salmonella enterica serovar Typhimurium (S. Typhimurium), 33 Salmonella enterica serovar Enteritidis (S. Enteritidis), 26 Klebsiella pneumonia (K. pneumoniae) and 130 Escherichia coli (E. coli) pig isolates collected from 1999–2006 were screened for β-lactam resistance by the disk diffusion test (DDT) and micro-broth dilution. Among the isolates, five E. coli and five K. pneumoniae exhibited reduced susceptibility to the cephalosporins tested. PCR, plasmid profiling and Southern blot hybridization showed the presence of multiple β-lactamases in these isolates of animal origin. Hybridization patterns of the DHA-1 specific probe indicated that dissemination of DHA-1 related β-lactamases could be attributed to plasmids of one common size among the enteric microbes of animal origin. To the best of our knowledge, this study reports the first identification of SHV-28 and DHA-1 from microbes of animal origin.