Fluoroquinolone resistance is a poor surrogate marker for type II topoisomerase mutations in clinical isolates of Streptococcus pneumoniae

The association between fluoroquinolone susceptibility and DNA mutations co ding for amino acid substitutions in the quinolone resistance-determining r egion was assessed with 44 clinical isolates of Streptococcus pneumoniae. T wenty-three strains bore at least one amino acid substitution. Only seven s trains with mutations were suggested by diminished susceptibility to ciprof loxacin (MTC, greater than or equal to2 pg/ml).