A comparative study of the in-vitro activity of levofloxacin against Streptococcus pneumoniae

In this study, the in-vitro activity of levofloxacin against Streptococcus pneumoniae was compared with the activities of a range of other antibiotics. In total, 320 penicillin-susceptible and 30 penicillin-intermediate clinical isolates of S. pneumoniae were collected in Germany between 1992 and 1994 from patients with bacteraemic pneumonia. MICs were determined using the agar dilution methodology recommended by the NCCLS and the results with levofloxacin compared with those with ofloxacin, D-ofloxacin, ciprofloxacin, amoxycillin, cefpodoxime, cefixime, cefuroxime, faropenem, erythromycin and tetracycline. Levofloxacin (MIC50 1 mg/L) was approximately twice as active against the isolates as ofloxacin (MIC50 2 mg/L). D-ofloxacin (MIC90 32 mg/L) showed no activity, while beta-lactam antibiotics showed elevated MIC90 values against penicillin-intermediate strains (amoxycillin, 1 mg/L; cefpodoxime, 2 mg/L; cefixime, 32 mg/L; cefuroxime, 8 mg/L) in comparison with the MIC90 obtained with penicillin-susceptible strains (amoxycillin, 0.015 mg/L; cefpodoxime, 0.03 mg/L; cefixime, 0.5 mg/L; cefuroxime, 0.03 mg/L). Faropenem showed good activity against pneumococcal isolates (penicillin-susceptible strains, MIC90 0.016 mg/L; penicillin-intermediate strains, MIC90 0.25 mg/L). Erythromycin (MIC90 8 mg/L) and tetracycline (MIC90 64 mg/L) were also less active against penicillin-intermediate pneumococcal isolates. In conclusion, levofloxacin and faropenem may be useful in the treatment of pneumococcal infections caused by organisms with decreased susceptibility to penicillin.