title: Antimicrobial resistance and class 1 integron-associated gene cassettes in Salmonella enterica serovar Typhimurium isolated from pigs at slaughter and abattoir environment.
abstract: Forty-five multi-resistant Salmonella enterica subsp. enterica serovar (S.) Typhimurium isolates obtained at five pig abattoirs in Southern Brazil were characterized. Their relatedness was determined by XbaI-macrorestriction analysis. Resistance genes, integrons and plasmid-mediated quinolone resistance genes (PMQR) were investigated by PCR. Amplicons for the variable part of class 1 integrons and the quinolone resistance-determining regions (QRDR) were sequenced. Plasmids were characterized by conjugation assays and replicon typing. Eighteen XbaI-macrorestriction patterns and 19 plasmid profiles were seen. Resistance to ampicillin (blaTEM), chloramphenicol (catA1 and floR), streptomycin (strA-strB), streptomycin/spectinomycin (aadA variants), sulphonamides (sul1, sul2, sul3) and tetracyclines [tet(A) and tet(B)] were commonly found. A trimethoprim resistance gene, dfrA8, was identified on a 100-kb plasmid. Single substitutions in the QRDR of GyrA but no PMQR genes were found. Twenty-five isolates carried class 1 integrons with an aadA23 gene cassette or unusual class 1 integrons with a dfrA12-orfF-aadA27 gene cassette array. Both integrons were found on large conjugative plasmids. Salmonella plasmid-located virulence genes spvR, spvA, spvB, rck and pefA were found on an IncFIB resistance plasmid. Hybrid virulence-resistance plasmids or plasmids harbouring class 1 integrons may play a role in the maintenance and dissemination of antimicrobial resistance among S. Typhimurium in this pig production system.
authors.affiliation: Departamento de Medicina Veterinária Preventiva, Universidade Federal do Rio Grande do Sul (UFGRS), Porto Alegre, Brazil; Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany.
authors.forename: Graciela Volz
authors.initials: GV
authors.lastname: Lopes
authors.affiliation: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany. Electronic address: geovana.michaelbrenner@fli.bund.de.
authors.forename: Geovana Brenner
authors.initials: GB
authors.lastname: Michael
authors.affiliation: Departamento de Medicina Veterinária Preventiva, Universidade Federal do Rio Grande do Sul (UFGRS), Porto Alegre, Brazil.
authors.forename: Marisa
authors.initials: M
authors.lastname: Cardoso
authors.affiliation: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwarz
mesh_terms: D000003:Abattoirs; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001938:Brazil; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D032023:Integrons / Q000235:genetics*; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics* / Q000472:pathogenicity; D013552:Swine; D014774:Virulence / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents
keywords: Co-selection; Food-producing animals; Hybrid virulence-resistance plasmids; Unusual class 1 integron