title: Genetic analysis of multi-drug resistance and the clonal dissemination of beta-lactam resistance in Salmonella Infantis isolated from broilers.
abstract: 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.
authors: Laboratory of Veterinary Public Health, Department of Veterinary Medicine, Faculty of Agriculture, Kagoshima University, 1 21-24 Korimoto, Kagoshima 890-0065, Japan.
authors: Francis
authors: F
authors: Shahada
authors: Haruhisa
authors: H
authors: Sugiyama
authors: Takehisa
authors: T
authors: Chuma
authors: Masuo
authors: M
authors: Sueyoshi
authors: Karoku
authors: K
authors: Okamoto
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D015994:Incidence; D032023:Integrons / Q000235:genetics; D007564:Japan / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D011200:Poultry; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology; D012475:Salmonella / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D012481:Salmonella Infections, Animal / Q000453:epidemiology / Q000382:microbiology; D018440:beta-Lactam Resistance / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial