Activities of six different quinolones against clinical respiratory isolates of Streptococcus pneumoniae with reduced susceptibility to ciprofloxacin in Spain.

Six quinolones were tested on 817 consecutive pneumococcal isolates for which ciprofloxacin MICs were high (> or =2 microg/ml); the isolates had been collected during two recent Spanish surveillance studies. For strains for which the ciprofloxacin MIC was >or =4 microg/ml, the MICs at which 90% of the isolates tested against gemifloxacin, moxifloxacin, gatifloxacin, sparfloxacin, levofloxacin, and ofloxacin were inhibited were 0.25, 1, 1, 1, 4 and 16 microg/ml, respectively, and the corresponding prevalences of resistance were 0, 1, 4.5, 9.5, 8.4 and 23%. The proportion of isolates for which the ciprofloxacin MIC is high has increased over time.