Synergistic combinations of antimicrobial agents against anaerobic bacteria.

Studies evaluating the in vitro and in vivo synergistic potential of combined antimicrobial agents against anaerobic bacteria are reviewed. Most studies evaluated therapy against Bacteroides sp. (mostly Bacteroides fragilis group). The combinations found to be most effective against B. fragilis were between metronidazole and clindamycin, spiramycin or gentamicin and between clindamycin and aminoglycosides. Against Bacteroides melaninogenicus the effective combinations were penicillin or clindamycin plus gentamicin and metronidazole and spiramycin or gentamicin. Occasional synergy was observed against Clostridium sp. and anaerobic cocci with clindamycin and gentamicin. Synergistic combinations have the potential of clinical use in serious anaerobic infections.