Mutant prevention concentrations of fluoroquinolones for clinical isolates of Streptococcus pneumoniae

Objective To determine the mutant prevention concentration(MPC) of fluoroquinolones to S.pneumoniae and explore its relationship with clinical pharmacokinetics.Methods The MICs to S.pneumoniae were determined with the standard two-fold agar dilution method.MPCs were measured with the bacterial inoculated 1010CFU/mL.Its relationship with pharmacokinetic parameters was discussed.Results Moxifloxacin had lower MPC values ranging from 0.5 mg/L to 2 mg/L.The MPC50 and MPC90 were 1 mg/L and 2 mg/L,respectively.The Cmax/MPC90 and AUC/MPC90 values were 2.2 and 19.7,respectively.The MPC50 and MPC90 of levofloxacin were 2 mg/L and 4 mg/L.Its MPC ranged from 2 mg/L to 4 mg/L.The Cmax/MPC90 and AUC/MPC90 values of levofloxacin 500 mg once daily were 2.2 and 19.7,which were the highest among the three dosing regimens.Conclusions The regimens like moxifloxacin 400 mg or levofloxacin 500 mg once daily has advantage in resistance mutation prevention.