Sélection in vitro de mutants résistants de Staphylococcus aureus en présence de fluoroquinolones par la méthode des passages successifs

The initial parental MICs for oflo and levo of methi-susceptible strains were included between 0.125 to 0.5 and 0.03 to 0.06mg/L respectively for trovafloxacin and moxifloxcin. The values for MRSA strains ranged from 1 to 4 and 0.125 to 0.5mg/L. The MICs of MSSA strains reached 64 to 128mg/L in 7 days with oflo and levo, 8 days with trova and 9 days moxi. The slopes were lower than 1.0 log with moxi (0.85) and higher than 1.2 log with the others components. MICs of MRSA rised quickly with oflo and levo (6 days). With moxi, MICs did not increase above 1mg/l for 6 days before reaching the final MIC in 10 days (16 to 32 mg/l). Selection of high level resistance (final MICs) was obtained with the 4 fluoroquinolones without differences of MIC between MSSA and MRSA.