Fluoroquinolone Resistance in Clinical Isolates ofStreptococcus pneumoniae: Contributions of Type II Topoisomerase Mutations and Efflux to Levels of Resistance

We report on amino acid substitutions in the quinolone resistance-determining region of type II topisomerases and the prevalence of reserpine-inhibited efflux for 70 clinical isolates of S. pneumoniae for which the ciprofloxacin MIC is >/=4 microgram/ml and 28 isolates for which the ciprofloxacin MIC is