title: Integron-mediated multidrug resistance in a global collection of nontyphoidal Salmonella enterica isolates.
abstract: Salmonella enterica bacteria have become increasingly resistant to antimicrobial agents, partly as a result of genes carried on integrons. Clonal expansion and horizontal gene transfer may contribute to the spread of antimicrobial drug-resistance integrons in these organisms. We investigated this resistance and integron carriage among 90 isolates with the ACSSuT phenotype (resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline) in a global collection of S. enterica isolates. Four integrons, dfrA12/orfF/aadA2, dfrA1/aadA1, dfrA7, and arr2/blaOXA30/cmlA5/aadA2, were found in genetically unrelated isolates from 8 countries on 4 continents, which supports a role for horizontal gene transfer in the global dissemination of S. enterica multidrug resistance. Serovar Typhimurium isolates containing identical integrons with the gene cassettes blaPSE1 and aadA2 were found in 4 countries on 3 continents, which supports the role of clonal expansion. This study demonstrates that clonal expansion and horizontal gene transfer contribute to the global dissemination of antimicrobial drug resistance in S. enterica.
authors.affiliation: Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Mary G
authors.initials: MG
authors.lastname: Krauland
authors.forename: Jane W
authors.initials: JW
authors.lastname: Marsh
authors.forename: David L
authors.initials: DL
authors.lastname: Paterson
authors.forename: Lee H
authors.initials: LH
authors.lastname: Harrison
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D014943:Global Health; D006801:Humans; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000382:microbiology / Q000635:transmission; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D012703:Serotyping
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins