Comparative in-vitro activity of trovafloxacin and other related drugs against isolates of streptococcus oralis

Objective: The in-vitro activity of trovafloxacin a new quinolone was compared with that of ciprofloxacin, erythromycin, various β-lactam and other appropriate antibiotics such as vancomycin, teicoplanin and clindamycin against 60 isolates of S. oralis. Methods: Minimal inhibitory concentration was performed using the agar dilution technique and microtiter method. In addition minimal bactericidal concentration and time-kill studies were carried out to estimate the bactericidal activity of trovafloxacin against S. oralis isolates. Results: Trovafloxacin showed a four-fold increase in activity over ciprofloxacin, with a narrow minimal inhibitory concentration range, MIC50 and mode values of 0.25 mg/l. Although the minimal inhibitory concentrations of trovafloxacin for S. oralis were relatively high compared to all the antibiotics tested. The in-vitro bactericidal activity of Trovafloxacin was greater than all other antibiotics against S. oralis. Five out of 10 isolates showed there was a 100% kill within 6 hours of contact; in all other cases, the kill time was between 6 and 24 hours. Conclusion: Overall, trovafloxacin showed superior minimal inhibitory concentration, bactericidal concentration and kill time when compared with different antibiotics.