Activity of moxifloxacin and twelve other antimicrobial agents against 216clinical isolates of Streptococcus pneumoniae

Background: An increased incidence of macrolide resistance in penicillin-re sistant Streptococcus pneumoniae has been described. Methods: With this in mind, 216 S. pneumoniae isolates were evaluated for their in vitro suscepti bility to a new fluoroquinolone, moxifloxacin, which was compared with peni cillin, amoxicillin, cefuroxime, cefotaxime, ceftriaxone, erythromycin, cla rithromycin, ciprofloxacin, sparfloxacin, ofloxacin, vancomycin and teicopl anin. A broth microdilution assay was performed in cation-adjusted Mueller- Hinton broth with 5% (v/v) lysed horse blood according to NCCLS guidelines. Results: Erythromycin resistance was observed in all the 22 penicillin-res istant S. pneumoniae (10.1%). All the penicillin-susceptible S. pneumoniae were susceptible to cephalosporins, whereas all the penicillin-resistant on es showed resistance to cefuroxime and only intermediate susceptibility to cefotaxime and ceftriaxone. The 216 tested strains were inhibited by sparfl oxacin and moxifloxacin at concentrations of 0.12-0.5 mg/l and 0.06-0.25 mg /l, respectively, regardless of whether the strain was penicillin and/or er ythromycin resistant. Seven penicillin-resistant strains displayed resistan ce to ofloxacin. All isolates were susceptible to vancomycin; teicoplanin M IC values ranged from 0.03 to 0.12 mg/l. The excellent in vitro activity of moxifloxacin against S. pneumoniae was not affected by penicillin and/or m acrolides. Conclusion: Moxifloxacin appears to be a promising choice for th e treatment of pneumococcal infections, including situations where therapeu tic choices are limited due to penicillin and macrolide resistance. Copyrig ht (C) 2001 S. Karger AG, Basel.