Antibiotic Resistance and Virulence Genes in Commensal Escherichia coli and Salmonella Isolates from Commercial Broiler Chicken Farms

• Published in: Journal of food protection 2007-06, Vol.70 (6), p.1316-1327
• Main Authors: Diarrassouba, F, Diarra, M.S, Bach, S, Delaquis, P, Pritchard, J, Topp, E, Skura, B.J
• Format: Article
• Language: English
• Subjects: Animal productions; Animals; Anti-Bacterial Agents - administration & dosage; Anti-Bacterial Agents - pharmacology; antibiotic resistance; antibiotics; bacterial contamination; Biological and medical sciences; broiler chickens; broiler feeding; Chickens - microbiology; Colony Count, Microbial - veterinary; Dose-Response Relationship, Drug; Drug Resistance, Bacterial; Drug Resistance, Multiple, Bacterial; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - isolation & purification; food contamination; Food Contamination - prevention & control; Food industries; Food Microbiology; food pathogens; Fundamental and applied biological sciences. Psychology; genes; growth regulators; Humans; isolation; medicated feeds; multiple drug resistance; on-farm food safety; Public Health; Risk Factors; Salmonella; Salmonella - drug effects; Salmonella - genetics; Salmonella - isolation & purification; serotypes; Terrestrial animal productions; Vertebrates; virulence; Virulence - genetics; virulence genes; Zoonoses
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028x-70.6.1316

Antibiotic resistance patterns and the presence of antibiotic and virulence determinants in 74 sorbitol-negative Escherichia coli and 62 Salmonella isolates from nine different broiler chicken farms were investigated. Each farm was supplied by one of three companies that used different antimicrobial agents in feed for growth promotion. The isolates were identified by API 20E for E. coli and by serological tests for Salmonella. The susceptibility of the isolates to antibiotics was determined by Sensititre using the Clinical and Laboratory Standards Institute's breakpoints. Fifty-two E. coli isolates (70.3%) and nine Salmonella isolates (14.52%) were multiresistant to at least nine antibiotics. The multiresistant isolates were evaluated for the presence of tetracycline resistance, integron class 1, and bla(CMY-2) genes by PCR. Of the 74 E. coli isolates, 55 were resistant to amoxicillin and ceftiofur. Among these 55 resistant E. coli isolates, 45 (81.8%) and 22 (40.0%) were positive for bla(CMY-2) and qacEdelta1-SulI genes, respectively. Tetracycline resistance was found in 56 isolates (75.8%) among which 12 (21.4%) and 24 (42.9%) gave positive results for tetA and tetB, respectively. Virulence genes (iss, tsh, and traT), aerobactin operon (iucC), and the eaeA gene were detected in some E. coli strains. Among the 27 amoxicillin- and ceftiofur-resistant Salmonella isolates, the bla(CMY-2) gene was detected in 22 isolates. The class 1 integron gene (qacEdelta1-SulI) was not detected in any Salmonella isolates, whereas the invasin (inv) and virulence (spv) genes were found in 61 (98.4%) and 26 (42%) of the Salmonella isolates, respectively. This study indicated that multiple antibiotic-resistant commensal E. coli and Salmonella strains carrying virulence genes can be found on commercial broiler chicken farms and may provide a reservoir for these genes in chicken production facilities. Except for the presence of tetB, there was no significant effect of feed formulations on the phenotypic or genotypic characteristics of the isolates.