| 19665854 |
Shahada F, Sugiyama H, Chuma T, Sueyoshi M, Okamoto K: Genetic analysis of multi-drug resistance and the clonal dissemination of beta-lactam resistance in Salmonella Infantis isolated from broilers. Vet Microbiol. 2010 Jan 6;140(1-2):136-41. Epub 2009 Jul 10.
An epidemiologic study was conducted to investigate the incidence and characterize the antimicrobial resistance determinants, analyzing plasmid profiles, and establishing the genetic relationship among beta-lactam-resistant isolates of Salmonella Infantis from broilers in Southern Japan. A total of 120 isolates were recovered from 56 flocks belonging to 44 holdings during 2004-2006. The percentages of resistance were as follows: ampicillin (24%), cephalothin (23%), cefoxitin (0%), ceftazidime (11%), cefotaxime (11%), chloramphenicol (0%), kanamycin (7.5%), ofloxacin (20%), oxytetracycline, streptomycin and sulfamethoxazole (100%) and trimethoprim (75%). The incidence of bla (TEM)-encoded beta-lactam resistance in 2004-2006 was significantly higher than in 1998-2003 (P <0.001). BlnI-digested PFGE patterns generated two related clusters implicated in the dissemination of beta-lactam resistance. Two types of plasmid profiles were observed and two plasmids of ca. 50 and 180-kb size were carried by beta-lactam-resistant isolates. Streptomycin resistance was conferred by aadA1 (n=116), aadA1-aadA2 (n=1), and aadA1-strA-strB (n=3). Resistances to kanamycin, oxytetracycline, sulfamethoxazole and trimethoprim were conferred by aphA1 (n=9, 100%), tetA (n=120, 100%) sul1 (n=120, 100%) and dfrA5 (n=90, 100%), respectively. Two types of class 1 integrons were detected: 1.0 kb (n=120) and, 1.0/1.5 kb (n=3). Integrons of 1.0/1.5 kb were found in isolates with the aadA1-strA-strB gene combination. For the first time, all S. Infantis isolates showed resistance to at least three classes of antimicrobial agents; and the intestinal tract of healthy poultry was a reservoir of the extended-spectrum cephalosporin-resistant isolates of serovar Infantis. |
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