Trovafloxacin susceptibility of aerobic clinical bacterial isolates from Sweden

Trovafloxacin susceptibility was studied in aerobic clinical isolates of ba cterial pathogens from 5 microbiology laboratories in Sweden. Trovafloxacin and ciprofloxacin minimum inhibitory concentration (MIC) determinations we re performed on 474 clinical isolates. Disk diffusion tests using trovaflox acin and ciprofloxacin 10 mu g disks were performed on a total of 7142 clin ical isolates (trovafloxacin). Susceptibility interpretations for trovaflox acin and ciprofloxacin were determined from MIC values and disk diffusion t ests using species-related MIC-limits and zone diameter breakpoints. Eight of 12 Gram-positive species groups were fully susceptible to trovafloxacin as judged by MIC tests. Trovafloxacin gave MIC50 values of 0.032 mg/l for S . aureus, 1.0 mg/l for MRSA, 0.064 mg/L for coagulase negative staphylococc i, 1.0 mg/l for MRSE, 0.064 mg/l for S, saprophyticus, 0.125 mg/l for group A and group B streptococci, 0.064 mg/l for group C and G streptococci and S. pneumoniae, 0.25 mg/l for E. faecalis, and 16.0 mg/l for E. faecium. The se MIC values were 4-16-fold lower than those of ciprofloxacin. Both MIC an d disk tests showed similar levels of susceptibility among Gram-negative is olates for trovafloxacin and ciprofloxacin. For most Gram-negative species the trovafloxacin MIC50 values were similar to or slightly higher than thos e for ciprofloxacin. Trovafloxacin MIC values were much lower for Acinetoba cter strains. but higher for P. mirabilis compared with ciprofloxacin. The favourable susceptibility levels of Swedish aerobic pathogens to trovafloxa cin emphasize the potential of this drug for the treatment of serious infec tions.