title: Antimicrobial resistance and virulence genes in Salmonella enterica isolates from dairy cows.
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.
authors.affiliation: Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand. rchuanchuen@yahoo.com
authors.forename: Rungtip
authors.initials: R
authors.lastname: Chuanchuen
authors.forename: Kittisak
authors.initials: K
authors.lastname: Ajariyakhajorn
authors.forename: Chailai
authors.initials: C
authors.lastname: Koowatananukul
authors.forename: Wechsiri
authors.initials: W
authors.lastname: Wannaprasat
authors.forename: Sirintip
authors.initials: S
authors.lastname: Khemtong
authors.forename: Sukuma
authors.initials: S
authors.lastname: Samngamnim
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology*; D003227:Conjugation, Genetic; D003612:Dairying; D004197:Disease Reservoirs / Q000662:veterinary; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005243:Feces / Q000382:microbiology; D005517:Foodborne Diseases / Q000517:prevention & control; D018014:Gene Transfer Techniques; D019450:Genes, MDR; D014644:Genetic Variation; D032023:Integrons / Q000235:genetics; D008826:Microbial Sensitivity Tests / Q000706:statistics & numerical data; D016133:Polymerase Chain Reaction; D012007:Rectum / Q000382:microbiology; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D013785:Thailand; D014774:Virulence / Q000235:genetics*