Genetic Characterization of Fluoroquinolone-Resistant Streptococcus pneumoniae Strains Isolated during Ciprofloxacin Therapy from a Patient with Bronchiectasis

Five Spain(9V-3) Streptococcus pneumoniae strains were isolated from a patient with bronchiectasis who had received long-term ciprofloxacin therapy. One ciprofloxacin-susceptible strain was isolated before treatment, and four ciprofloxacin-resistant strains were isolated during treatment. The resistant strains were derived from the susceptible strain either by a parC mutation (low-level resistance) or by parC and gyrA mutations (high-level resistance). This study shows that ciprofloxacin therapy in a patient colonized by susceptible S. pneumoniae may select fluoroquinolone-resistant mutants. We thank A. Fenoll, Spanish Pneumococcus Reference Laboratory (Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid), for checking serotypes. We thank M. A. Dominguez for performing the PFGE analysis and critically reading the manuscript. This work was supported by grants 00/0258 and 01/1267 from the Fondo de Investigación Sanitaria and by grant BIO2002-01398 from the Ministerio de Ciencia y Tecnología.