ABSTRACT
OBJECTIVE: To evaluate the antibacterial activity of levofloxacin, moxifloxacin and nemonoxacin against Staphylococcus aureus in vitro. To assesse the impact of gyrA and parC genes mutant on resistance for quinolones and the sequences of gyrA and parC genes for three quinolones. METHODS: The MICs of 50 S. aureus were detected by agar dilution method. The MIC and MPC against four S. aureus which were special gene mutations were detected by agar dilution method. Based on these results, bacterial recovery growth curve of levofloxacin, moxifloxacin and nemonoxacin were traced. RESULTS: Nemonoxacin demonstrated activities 8- to 32- fold more potent(MICs at which 90% of isolates were inhibited, 0.5 μg·mL-1) than those of moxifloxacin(MIC90, 2 μg·mL-1) and levofloxacin (MIC90, 16 μg·mL-1) against 50 S. aureus.In condition of the same drug concentrations, the bacterial recovery growth ratios of nemonoxacin was the lowest, while levofloxacin's was the highest. RN450A3 recovery growth ratio was highest compared with other mutant bacterial strains, while RN450 recovery growth ratio was lowest. CONCLUSION: The antibacterial activities of nemonoxacin, moxifloxacin and levofloxacin against S. aureus in vitro are:nemonoxacin> moxifloxacin >levofloxacin. Compared with levofloxacin and moxifloxacin, nemonoxacin inhibits bacteria in a lower concentration, and nemonoxacin is utterly efficacious with different genes mutant strains.The target preference of levofloxacin may be the parC gene of topoisomerase IV, while moxifloxacin and nenomoxacin can almost act on the gyrA and parC gene at the same time.