The most frequent markers of fluoroquinolone resistance in S. pneumoniae are chromosomal mutations in the quinolone-resistance-determining regions of DNA gyrase and topoisomerase IV encoding for the gyrA, gyrB and parC, parE genes. In 2008, 6.5% of the Streptococcus pneumoniae isolates in a Bangkok university hospital were resistant to ofloxacin. Using PCR and DNA sequencing, we identified mutations in both the gyrA and parC genes of four ofloxacin- and ciprofloxacin-resistant S. pneumoniae isolates (minimum inhibitory concentrations32 microg/ml). Mutations were found in the gyrA gene at positions Ser81Phe, Glu85Gly, Glu85Lys and in the parC gene at position Ser79Tyr. Three isolates had mutations in both genes. Two of the isolates were serotype 6B and two were serotypes not contained in currently licensed pneumococcal vaccines. This is the first report of the mechanisms of fluoroquinolone resistance in S. pneumoniae in Thailand.
