In vivo development of high-level fluoroquinolone resistance in Streptococcus pneumoniae in chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease are generally subjected to multiple regimens of antimicrobial treatment. The development of high-level levofloxacin resistance (i.e., a minimum inhibitory concentration >8 mu g/mL) in 8 patients whose previous pneumococcal isolates showed susceptibility is described. Molecular methods were used to characterize the strains and to study the sequential changes in fluoroquinolone targets.