The genetic basis for phenicol resistance was examined in 38 phenicol-resistant clinical Escherichia coli isolates from poultry. Out of 62 isolates, 38 showed resistance for chloramphenicol and nine for florfenicol, respectively. Each strain also demonstrated resistance to a variety of other antibiotics. Molecular detection revealed that the incidence rates of the cat1, cat2, flo, flo-R, cmlA, and cmlB were 32, 29, 18, 13, 0, and 0%, respectively. Nineteen strains were tolerant to organic solvents. PCR amplification of the complete acrR (regulator/repressor) gene of five isolates revealed the amino acid changes in four isolates. DNA sequencing showed the non-synonymous mutations which change the amino acid, silent mutation, and nucleotide deletion in four isolates. MY09C10 showed neither deletion nor mutation in nucleotide. The AcrA protein of the AcrAB multidrug efflux pump was overexpressed in these strains. Complementation with a plasmid-borne wild-type acrR gene reduced the expression level of AcrA protein in the mutants and partially restored antibiotic susceptibility one- to fourfold. This study shows that mutations in acrR are an additional genetic basis for phenicol resistance.

• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Genes, Bacterial genetics   MeSH
• DNA, Bacterial genetics   MeSH
• Escherichia coli drug effects   genetics   isolation & purification   MeSH
• Genotype MeSH
• Chickens MeSH
• Membrane Transport Proteins genetics   MeSH
• Microbial Sensitivity Tests veterinary   MeSH
• Drug Resistance, Multiple, Bacterial drug effects   genetics   MeSH
• Mutation MeSH
• Poultry Diseases microbiology   MeSH
• Escherichia coli Proteins genetics   MeSH
• Gene Expression Regulation, Bacterial MeSH
• Repressor Proteins genetics   MeSH
• Chloramphenicol Resistance drug effects   genetics   MeSH
• Genetic Complementation Test veterinary   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH