Detection and characterization of extended-spectrum beta-lactamase (TEM-52)-producing Salmonella serotype Infantis...

During 2004 and 2006, multidrug-resistant Salmonella enterica subspecies enterica serovar Infantis (Salmonella Infantis) isolates (n = 120) were recovered from broiler cecal samples collected from a meat-processing plant, and the isolates were examined. The study was conducted to detect and characterize extended-spectrum beta-lactamase (ESBL)-producing Salmonella Infantis isolates recovered from broiler chickens and determine the mechanisms of transfer of the resistance traits. Extended-spectrum cephalosporins-resistant Salmonella Infantis isolates producing ESBL TEM-52 were detected. The mutant bla(TEM-52) gene and the wild-type bla(TEM-1) gene that mediated resistance to ampicillin (an extended-spectrum penicillin) and cephalothin (a narrow-spectrum cephalosporin) were located on approximately 50-kb conjugative plasmids among beta-lactam-resistant (n = 29) isolates. The bla(TEM) genes did not cotransfer with aadA1, sul1 (both associated with class 1 integrons), tetA, and dfrA5, signifying a chromosomal location of these non-beta-lactam resistance-encoding genes. This is the first report describing TEM-52-producing S. enterica from food-producing animals in Japan. An emergence of TEM-type ESBL is an important concern to public health because this readily transferable resistance mechanism threatens the value of the third-generation cephalosporins and may reduce the clinical utility of this class of antibiotics against pathogenic Gram-negative bacteria.