Activity of moxifloxacin and other quinolones against pneumococci resistant to first-line agents, or with high-level ciprofloxacin resistance

Abstract

The activity of moxifloxacin and other quinolones was assessed against 288 epidemiologically diverse isolates of Streptococcus pneumoniae, many of them resistant to one or more first-line agents and/or with increased ciprofloxacin resistance (minimum inhibitory concentrations, MICs 16–>64 mg/l compared with 1–2 mg/l for most isolates). Moxifloxacin and grepafloxacin were the most active quinolone analogues, inhibiting about 90% of the isolates at ⩽1 mg/l, whereas levofloxacin inhibited 64% of isolates at ⩽1 mg/l and ciprofloxacin inhibited 42%. Moxifloxacin also was the most active agent against isolates with elevated ciprofloxacin resistance (MIC 16–>64 mg/l): moxifloxacin MICs of around 4 mg/l were seen for most such isolates, compared with 16–32 mg for levofloxacin and grepafloxacin. The activity of moxifloxacin against pneumococci resistant to one or more first-line agent suggests it will have a useful therapeutic role, although its activity against highly ciprofloxacin resistant isolates seems marginal.