[Study on the molecular mechanism of quinolone resistance in Shigellae spp].

OBJECTIVE: To study the resistance and its mechanism of Shigellae spp. to quinolones. METHODS: Seventy-three clinical isolates were collected. Susceptibility tests of pipemidic adcid (PI), ofloxacin (OFL), norfloxacin (NOR), and ciprofloxacin (CIP) were performed in all clinical isolates and Shigella 51573. The N-terminal coding region of gyrA and parC were amplified by polymerase chain reaction (PCR) respectively. Restriction fragment length polymorphism (RFLP) was applied to all PCR procucts of gyrA and parC, and single strand conformational polymorphism analysis (SSCP) was also applied to PCR procucts of parC. RESULTS: The resistance rates for all the Shigella spp. to PI, CIP, NOR and OFL were 79.5%, 60.3%, 41.1% and 36.9%. Sixty-seven strains (91.8%) were quinolone-reduced-sensitive isolates, in which 61 strains (91%) were found carrying mutations in gyrA with 5 strains (7.5%) found carrying mutations in parC. No mutation was found in 6 quinolone-sensitive isolates or Shigella 51573. CONCLUSION: The Shigella spp. had high resistance rates to quinolones. The target gene mutations which were mainly found in gyrA and secondarily in parC, played an important role in the quinolone-resistance in Shigella spp.