Fluoroquinolone resistance of Streptococcus pneumoniae isolates causing invasive disease: special focus on zabofloxacin.

The present study examined the in vitro activity of various antibiotics including zabofloxacin, against isolates responsible for invasive pneumococcal diseases. Between 1997 and 2008, a total of 208 isolates were collected from sterile fluids, including blood (n=196, 94.2%), pleural fluid (n=5, 2.4%), cerebrospinal fluid (n=5, 2.4%), and ascites (n=2, 1.0%). Zabofloxacin showed the lowest MIC50 (0.015μg/mL) and MIC90 (0.025μg/mL) values of all the tested antibiotics. Rates of isolates resistant to penicillin (MIC ≥8μg/mL), ceftriaxone (MIC ≥4μg/mL) and levofloxacin (MIC ≥8μg/mL) were 3.4%, 0.4% and 2.0%, respectively. Four isolates (2.0%) were resistant to levofloxacin, and zabofloxacin showed low MICs (range, 0.025–0.125μg/mL). Zabofloxacin shows potent in vitro activity against S. pneumoniae isolates that caused invasive disease, even strains that are resistant to levofloxacin.