Antimicrobial resistance and virulence genes in Salmonella enterica isolates from dairy cows

Foodborne Pathog Dis. 2010 Jan;7(1):63-9. doi: 10.1089/fpd.2009.0341.

Abstract

One hundred sixty Salmonella enterica isolates from clinically healthy dairy cows were assayed for antibiotic susceptibilities, the presence of class 1 integrons, antimicrobial resistance genes and virulence genes, and conjugal transfer of antimicrobial resistance determinants. One hundred nine (68%) of the Salmonella isolates were resistant to at least 1 antibiotic, and 14 isolates (9%) were multiresistant. The most prevalent resistance observed was to streptomycin (64%). Class 1 integrons were detected in only two Salmonella isolates (serovar Singapore and Derby), and both integrons harbored the same cassette content aadA2. The Derby class 1 integrons were associated with Salmonella genomic island 1-A. Most commonly found resistance genes were strA and strB (9.2%). None of class 1 integrons were horizontally transferred, and the resistance genes were successfully transferred from six (5.5%) Salmonella strains. One hundred fifty-nine isolates (98.8%) were positive to the invasion gene invA, whereas the virulence plasmid-associated genes spvC and pefA were found in only two (1.3%) and one (0.6%) Salmonella isolates, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle / microbiology*
  • Conjugation, Genetic
  • Dairying*
  • Disease Reservoirs / veterinary
  • Drug Resistance, Bacterial / genetics*
  • Drug Resistance, Multiple, Bacterial / genetics
  • Feces / microbiology
  • Foodborne Diseases / prevention & control
  • Gene Transfer Techniques
  • Genes, MDR
  • Genetic Variation
  • Integrons / genetics
  • Microbial Sensitivity Tests / statistics & numerical data
  • Polymerase Chain Reaction
  • Rectum / microbiology
  • Salmonella enterica / drug effects*
  • Salmonella enterica / genetics
  • Salmonella enterica / isolation & purification
  • Salmonella enterica / pathogenicity*
  • Thailand
  • Virulence / genetics*