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

BACKGROUND

An increased incidence of macrolide resistance in penicillin-resistant Streptococcus pneumoniae has been described.

METHODS

With this in mind, 216 S. pneumoniae isolates were evaluated for their in vitro susceptibility to a new fluoroquinolone, moxifloxacin, which was compared with penicillin, amoxicillin, cefuroxime, cefotaxime, ceftriaxone, erythromycin, clarithromycin, ciprofloxacin, sparfloxacin, ofloxacin, vancomycin and teicoplanin. 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-resistant S. pneumoniae (10.1%). All the penicillin- susceptible S. pneumoniae were susceptible to cephalosporins, whereas all the penicillin-resistant ones showed resistance to cefuroxime and only intermediate susceptibility to cefotaxime and ceftriaxone. The 216 tested strains were inhibited by sparfloxacin and moxifloxacin at concentrations of 0.12-0.5 mg/l and 0.06-0.25 mg/l, respectively, regardlesss of whether the strain was penicillin and/or erythromycin resistant. Seven penicillin-resistant strains displayed resistance to ofloxacin. All isolates were susceptible to vancomycin; teicoplanin MIC 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 macrolides.

CONCLUSION

Moxifloxacin appears to be a promising choice for the treatment of pneumococcal infections, including situations where therapeutic choices are limited due to penicillin and macrolide resistance.