Comparative in vitro activity of cider and newer fluoroquinolones against respiratory tract pathogens

The aim of this study was to evaluate the antibacterial activity of older ( ciprofloxacin and ofloxacin) and newer (moxifloxacin, grepafloxacin, sparfl oxacin and levofloxacin) fluoroquinolones. Minimal inhibitory concentration s (MICs) were determined, according to the NCCLS guidelines, against the fo llowing respiratory tract pathogens: penicillin-susceptible and -resistant Streptococcus pneumoniae, beta-lactamase-positive and beta-lactamase-negati ve Haemophilus influenzae and beta-lactamase-positive Moraxella catarrhalis . In addition, we evaluated the minimal bactericidal concentrations of the same antibiotics against all the pneumococci and the haemophili. Finally, t he activity of ciprofloxacin, ofloxacin, sparfloxacin and moxifloxacin agai nst 15 pneumococci were investigated by time-kill analysis. All fluoroquino lones tested exhibited a similar, good activity against H. influenzae and M . catarrhalis. Against S. pneumoniae, irrespective of penicillin susceptibi lity, moxifloxacin, grepafloxacin, sparfloxacin and levofloxacin exhibited excellent activity, better than ciprofloxacin and ofloxacin. Time-kill anal ysis showed that 99.9% killing of all strains was obtained after 24 h with moxifloxacin at 2 x MIC, whereas other antimicrobials obtained similar resu lts at 4 x MIC. Moxifloxacin is characterized by an improved activity again st respiratory pathogens, including penicillin-resistant and -susceptible S . pneumoniae. Its activity is not influenced by beta-lactamase production. These results suggest that moxifloxacin represents a promising alternative for treatment of respiratory tract infections. Copyright (C) 2000 S. Karger AG, Basel.