Genetic analysis of multi-drug resistance and the clonal dissemination of β-lactam resistance in Salmonella Infantis isolated from broilers

• Published in: Veterinary microbiology Vol. 140; no. 1-2; pp. 136 - 141
• Main Authors: Shahada, Francis, Sugiyama, Haruhisa, Chuma, Takehisa, Sueyoshi, Masuo, Okamoto, Karoku
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 06-01-2010; Amsterdam; New York: Elsevier; Elsevier
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; antibiotic resistance; Bacteriology; beta-lactam antibiotics; beta-Lactam Resistance - genetics; Biological and medical sciences; broiler chickens; cephalosporins; clonal variation; clones; defense mechanisms; disease reservoirs; disease surveillance; DNA, Bacterial - genetics; Drug Resistance, Multiple, Bacterial - genetics; epidemiological studies; Fundamental and applied biological sciences. Psychology; gastrointestinal system; genes; genetic variation; Incidence; integrons; Integrons - genetics; Japan - epidemiology; microbial genetics; Microbial Sensitivity Tests; Microbiology; Miscellaneous; Molecular epidemiology; multiple drug resistance; pathotypes; Phylogeny; plasmids; Plasmids - genetics; Poultry; poultry diseases; Poultry Diseases - epidemiology; Poultry Diseases - microbiology; Resistance epidemiology; risk assessment; Salmonella - classification; Salmonella - drug effects; Salmonella - genetics; Salmonella - isolation & purification; Salmonella enterica subsp. enterica serovar Infantis; Salmonella Infantis; Salmonella Infections, Animal - epidemiology; Salmonella Infections, Animal - microbiology; salmonellosis; strains; Japan; Resistance epidemiology; Molecular epidemiology; Salmonella Infantis; Resistance; Salmonella; Dissemination; β-Lactams; Bacteria; Genotype; Genetics; Veterinary; Enterobacteriaceae
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2009.07.007

An epidemiologic study was conducted to investigate the incidence and characterize the antimicrobial resistance determinants, analyzing plasmid profiles, and establishing the genetic relationship among β-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 blaTEM-encoded β-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 β-lactam resistance. Two types of plasmid profiles were observed and two plasmids of ca. 50 and 180-kb size were carried by β-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: 1.0kb (n=120) and, 1.0/1.5kb (n=3). Integrons of 1.0/1.5kb 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.