Detection and coexistence of six categories of resistance genes in Escherichia coli strains from chickens in Anhui Province, China

Abstract

The aim of this study was to characterise the prevalence of class 1 integrons and gene cassettes, tetracycline-resistance genes, phenicol-resistance genes, 16S rRNA methylase genes, extended-spectrum β-lactamase genes and plasmid-mediated fluoroquinolone resistance determinants in 184 Escherichia coli isolates from chickens in Anhui Province, China. Susceptibility to 15 antimicrobials was determined using broth micro-dilution. Polymerase chain reaction and DNA sequencing were used to characterise the molecular basis of the antibiotic resistance. High rates of antimicrobial resistance were observed; 131 out of the 184 (72.3%) isolates were resistant to at least six antimicrobial agents. The prevalences of class 1 integrons, tetracycline-resistance genes, phenicol-resistance genes, 16S rRNA methylase genes, extended-spectrum β-lactamase genes and plasmid-mediated fluoroquinolone resistance determinants were 49.5, 17.4, 15.8, 0.5, 57.6 and 46.2%, respectively. In 82 isolates, 48 different kinds of coexistence of the different genes were identified. Statistical (χ2) analysis showed that the resistance to amoxicillin, doxycycline, florfenicol, ofloxacin and gentamicin had significant differences (P<0.01 or 0.01<P<0.05) among the strains that carried and did not carry the resistance genes, which showed a certain correlation between antimicrobial resistance and the presence of resistance genes.

Keywords

• Escherichia coli
• Antimicrobial resistance
• Chicken
• Coexistence