title: Characterization of drug resistant Salmonella enterica serotype Typhimurium by antibiograms, plasmids, integrons, resistance genes and PFGE.
abstract: Forty-seven Salmonella Typhimurium (33 zoonotic, 14 clinical) strains were tested for antimicrobial resistance using the standard disk diffusion method. Presence of relevant resistance genes and class 1 integrons were investigated by using PCR. Pulsed-field gel electrophoresis (PFGE) and plasmid profiling were carried out to determine the genomic diversity of Salmonella Typhimurium. Approximately 57.4% of S. Typhimurium were multidrug resistant (MDR) and showed high resistance rates to tetracycline (70.2%), sulphonamides (57.4%), streptomycin (53.1%), ampicillin (29.7%), nalidixic acid (27.6%), kanamycin (23.4%), chloramphenicol (21.2%) and trimethoprim (19.1%). Resistance towards cephalosporins was noted for cephalothin (27.6%), cephradine (21.2%), amoxicillin clavulanic acid (17.0%) and cephalexin (17.0%). Resistance genes, blaTEM, strA, aadA, sul1, sul2, tet(A), tet(B) and tet(C) were detected among the drug resistant strains. Thirty-three strains (70.2%) carried class 1 integrons, which were grouped in 9 different profiles. DNA sequencing identified sat, aadA, pse-1 and dfrA genes in variable regions on class 1 integrons. Thirty-five strains (74.4%) were subtyped to 22 different plasmid profiles, each with 1 - 6 plasmids (2.0 to 95 kb). PFGE subtyped the 47 strains into 39 profiles. In conclusion, high rates of multidrug-resistance were found among the Malaysian Salmonella Typhimurium strains. The emergence of multidrug-resistant Salmonella Typhimurium to cephalosporin antibiotics was also observed. The strains were very diverse and no persistent clone was observed. The emergence of MDR Salmonella Typhimurium is a worldwide problem and this report provides information for the better understanding of the prevalence and epidemiology of MDR S. Typhimurium in Malaysia.
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia.
authors.forename: Douadi
authors.initials: D
authors.lastname: Benacer
authors.forename: Kwai-Lin
authors.initials: KL
authors.lastname: Thong
authors.forename: Haruo
authors.initials: H
authors.lastname: Watanabe
authors.forename: Savithri Devi
authors.initials: SD
authors.lastname: Puthucheary
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002417:Cattle; D002645:Chickens; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D032023:Integrons; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics*; D012480:Salmonella Infections / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D013552:Swine
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins