Fluoroquinolone Resistance in Clinical Isolates of Streptococcus pneumoniae from Asian Countries: ANSORP Study

Seventeen clinical isolates of Streptococcus pneumoniae showing reduced susceptibility to ciprofloxacin (MIC ≥ 4 μg/ml) collected from eight different Asian countries were analyzed by antimicrobial susceptibility, serotyping, pulsed-field gel electrophoresis (PFGE), and DNA sequencing of the quinolone resistance-determining regions (QRDRs) in gyrA, gyrB, parC, and parE. All isolates but one showed more than one amino acid alteration in QRDRs of four responsible genes. Ile460 → Val in parE was the most common mutation. Data suggest that Lys137 → Asn in parC may be a primary step in the development of high-level and multiple FQ resistance. An additional mutation of Ser81 → Phe in gyrA resulted in high-level resistance to ciprofloxacin, levofloxacin, and gatifloxacin, whereas Ser79 → Phe in parC may exert an important role in the development of moxifloxacin resistance. Two novel amino acid changes in gyrB, Ala390 → Val and Asn423 → Thr, were found. Data from PFGE suggest an introduction and local spread of multiple resistant Spain^23F-1 clone in Hong Kong, but isolates from other Asian countries were not related to this clone.