[Fluoroquinolone resistance mutations in topoisomerase genes of Salmonella typhimurium isolates].Wei Sheng Yan Jiu. 2004 Sep; 33(5):591-4.WS
Mutations in topoisomerase genes were main cause of the resistence of Salmonella typhimurium to fluoroquinolone.
The MICs of three Salmonella typhimurium isolates X2, X7, X11 to ciprofloxacin were above 32 microg/ml, 0.38 microg/ml and 0.023 microg/ml, respectively. The genetic alterations in four topoisomerase genes, gyrA, gyrB, parC, and parE were detected by multiplex PCR amplimer conformation analysis in these three strains.
X2 isolate showed both gyrA mutations (Ser83-->Phe, Asp87-->Asn) and parC mutation (Ser80-->Arg). X7 isolate showed a single gyrA mutation (Ser83-->Phe) and X11 isolate had no changes in all of the four quinolone resistance genes, gyrA, gyrB, parC, and parE. X7 isolate with a single gyrA mutation was less resistant to ciprofloxacin than X2 with double gyrA mutations and an additional parC mutation.
GyrA and parC genes play important role of the resistance of Salmonella typhimurium to ciprofloxacin.