Effects of pH and Incubation Time on Susceptibility of Ureaplasma urealyticum to Levofloxacin,Sparfloxacin and Gatifloxacin in vitro

OBJECTIVE To determine the effects of pH and incubation time on the susceptibility of Ureaplasma urealyticum to levofloxacin,sparfloxacin and gatifloxacin in vitro.METHODS With different pH at 6.0,6.5,and 7.0 and different incubation time for 24,36,48,and 60 hours,a multiple-proportional broth microdilution method was applied to detect the MICs of drugs mentioned above against 35 clinical specimens isolated from nongonococcal urethritis patients.RESULTS The MICs of 60 h were the same to that of 48 h.Gatifloxacin was the best against U.urealyticum,esp.when pH rose to more than 6.5,the sensitive rate was 100.0%.There was a high resistance rate for sparfloxacin.No matter what the medium pH was 6.0,6.5 or 7.0,the MICs of the levafloxacin,sparfloxacin and gatifloxacin were 1-32,1-8 and 1-16-fold increase,respectively(P0.05, respectively),and their MIC50、MIC90 and resistance rates were increased differently when incubation time was prolonged from 24h to 36h or 48h.As the medium pH increased from 6.0 to 6.5 or 7.0,the MICs of gatifloxacin or sparfloxacin decreased 1-to 8-folds(P0.05),and MIC50,MIC90 and resistance rates were decreasing respectively,whether the incubation time was 24,36 or 48 h.But the results of levafloxacin were reverse when pH changed.CONCLUSIONS The study suggests that the MICs of sparfloxacin and gatifloxacin to U.urealyticum increase markedly as incubation time prolongs and decrease remarkably as the culture medium pH increases.The MICs of levafloxacin increase notably as incubation time prolongs and pH rises.Gatifloxacin has a good activity to U.urealyticum.Forty-eight hours can be the end-point for incubation time for MICs of U.urealyticum.