In-vitro activity of pefloxacin against micro-organisms multiply resistant to beta-lactam antibiotics and aminoglycosides.

The in-vitro activity of pefloxacin was evaluated against 360 Enterobacteriaceae, 143 Pseudomonas aeruginosa and 124 staphylococci, selected for multiply resistance to different beta-lactam antibiotics and aminoglycosides. The MIC90 of pefloxacin against staphylococci and most Enterobacteriaceae was 0.5 mg/l or less. The MIC90 against Serratia marcescens and P. aeruginosa varied between 4 and 8 mg/l. Time-killing curves showed that pefloxacin at concentrations of four times the MIC decreased the viable counts by 3 logs or more within 1-8 h.