Prevalence of Mutations within the Quinolone Resistance-Determining Region of gyrA , gyrB , parC , and parE and Association with Antibiotic Resistance in Quinolone-Resistant Salmonella enterica

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Abstract
Salmonella enterica isolates ( n = 182) were examined for mutations in the quinolone resistance-determining region of gyrA , gyrB , parC , and parE . The frequency, location, and type of GyrA substitution varied with the serovar. Mutations were found in parC that encoded Thr57-Ser, Thr66-Ile, and Ser80-Arg substitutions. Mutations in the gyrB quinolone resistance-determining region were located at codon Tyr420-Cys or Arg437-Leu. Novel mutations were also found in parE encoding Glu453-Gly, His461-Tyr, Ala498-Thr, Val512-Gly, and Ser518-Cys. Although it is counterintuitive, isolates with a mutation in both gyrA and parC were more susceptible to ciprofloxacin than were isolates with a mutation in gyrA alone.