Alteration ingyrA andparC Gene Associated with Fluoroquinolone Resistance ofEnterococcusspp. Isolated from Feces of Chicken

Abstract

The purpose of this study was to investigate the fluoroquinolone resistance frequency of Enterococcus spp. from normal chicken feces and to analyse mutations of the gyrA and parC gene associated with fluoroquinolone resistance. Among 52 Enterococcus faecalis and 25 E. faecium isolates, 23 (44.2%) E. faecalis and 7 (28.0%) E. faecium were resistant to ciprofloxacin (CIP) by disc diffusion method. Genetic exchange in gyrA and parC gene among 2 CIP intermediate isolates and 15 CIP resistant isolates were found in the amino acid codon of Ser-83 and Asp-87, and Ser-80 and Glu-84, respectively. These mutants contained a change from Ser to Phe, Val, Tyr, Ile, Thr or Pro at codon 83 and from Glu to Gly or Leu at codon 87 in gyrA gene, and a change from Ser to Ile or Thr at codon 80 and from Glu to Asp or Lys at codon 84 in parC gene. The isolates with mutation in gyrA regardless of a mutation in parC showed high resistance (MIC ≥32 μg/ml) to CIP, enrofloxacin, norfloxacin and ofloxacin. These results suggested that gyrA gene is the primary target for 4 fluoroquinolones resistance in Enterococcus spp.