[Activity of 5 fluoroquinolones on hospital Gram-negative bacilli with different sensitivities to pefloxacin]

The minimum inhibitory concentrations (MIC) of 5 fluoroquinolones, fleroxacin (FLE), ciprofloxacin (CIP), ofloxacin (OFL), enoxacin (ENO) and norfloxacin (NOR) have been determined by the agar dilution method towards 140 strains of Pseudomonas aeruginosa (Pa) and 146 Enterobacteriaceae showing different sensitivities to pefloxacin (PEF). The strains were isolated in 1988 at the Bellevue Hospital. The modal MIC is 0.12 for CIP, 0.25 for NOR, 0.5 for OFL, and 1 for FLE and ENO when used on Pa strains which are sensitive to PEF (n = 35) (MIC less than or equal to 1mg/1). The modal MIC is 0.25 - 0.5 for CIP, 0.5 for NOR, 1 for OFL and ENO, and 2 for FLE when used on Pa strains which are of intermediate sensitivity to PEF (n = 70) (1 less than MIC less than or equal to 4). The modal MIC is 2 for CIP, 8 for NOR and OFL, 8 - 16 for ENO, and 32 for FLE when used on Pa strains which are resistant to PEF (n = 35) (MIC greater than 4). The modal MIC is 0.015 for CIP, 0.06 for OFL, 0.12 for FLE, NOR and ENO when used on Escherichia coli strains which are sensitive to PEF (n = 47). The modal MIC is 0.5 for CIP, 1 for OFL and NOR, and 2 FLE and ENO, when used on Escherichia coli strains which are of intermediate sensitivity to PEF (n = 38). The modal MIC is 1 for CIP, 4 for OFL and NOR, 16 for FLE, and 32 for ENO when used on E coli strains which are resistant to PEF (n = 15). The 26 Serratia marcescens and 20 Citrobacter with MIC greater than or equal to 8 for PEF all have MICs greater than 1 and modal MICs greater than or equal to 4 for all the fluoroquinolones studied. CIP always showed greater activity than the other quinolones whatever the sensitivity shown towards PEF.