Antimicrobial resistance and class 1 integron-associated gene cassettes in Salmonella enterica serovar Typhimurium isolated from pigs at slaughter and abattoir environment

• Published in: Veterinary microbiology Vol. 194; pp. 84 - 92
• Main Authors: Lopes, Graciela Volz, Michael, Geovana Brenner, Cardoso, Marisa, Schwarz, Stefan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.10.2016
• Subjects: Abattoirs; Animals; Anti-Bacterial Agents - pharmacology; Brazil; Co-selection; Drug Resistance, Bacterial - genetics; Food-producing animals; Genes, Bacterial - genetics; Hybrid virulence-resistance plasmids; Integrons - genetics; Salmonella typhimurium - drug effects; Salmonella typhimurium - genetics; Salmonella typhimurium - pathogenicity; Swine; Unusual class 1 integron; Virulence - genetics; Unusual class 1 integron; Co-selection; Food-producing animals; Hybrid virulence-resistance plasmids
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2016.04.020

•Clonal relatedness of multi-resistant Salmonella Typhimurium from different origins.•Detection of an unusual class 1 integron on conjugative plasmids.•Identification of a hybrid virulence-resistance plasmid.•Multi-resistant porcine S. Typhimurium isolates as potential risk to human health. 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.