Bactericidal activity of Trovafloxacin and Moxifloxacin against Gram-negative anaerobic bacilli

Anaerobes are often involved in human pathology, including oral infections. The therapy of anaerobic infection requires certain antibiotics such as: metronidazole, tetracycline or amoxicillin. But the incidence of resistant strains among anaerobes is continuously increasing and it is necessary to find some new agents effective against these bacteria. The aim of our study was to establish the bactericidal activity of two new quinolones against 14 strains of gram-negative anaerobic bacilli. The MIC of tested strains was first detected and then time-kill kinetics was determined by using Miles and Misra methodology. Ciprofloxacin was used as standard-quinolone. The results show that trovafloxacin and moxifloxacin have good activity against anaerobes, better than that of ciprofloxacin. Bactericidal curves suggest a rapid action of moxifloxacin (within the first 4 hours), but a prolonged cidal activity for trovafloxacin (24 hours). For both agents, the antimicrobial effect is concentration-dependent. As previous studies suggest, the new quinolones have good activity against both aerobic and anaerobic bacteria so they are useful in the treatment of mixed infections (common feature of anaerobic infections).