BACTERICIDAL ACTIVITY OF SELECTED ANTIMICROBIAL AGENTS AGAINST BILOPHILA-WADSWORTHIA AND BACTEROIDES-GRACILIS

Bactericidal assays of Bacteroides gracilis (six strains) and Bilophil a wadsworthia (12 strains) in brucella broth with appropriate suppleme nts were performed by the time-kill kinetic method. Antimicrobial agen ts tested were ampicillin/sulbactam (final concentrations, 16/8 mug/mL ), ticarcillin/clavulanate (128/2 mug/mL), imipenem (8 mug/mL), cefoxi tin (32 mug/mL), chloramphenicol (16 mug/mL), clindamycin (4 mug/mL), and metronidazole (16 mug/mL). Although all antimicrobial agents teste d inhibited growth of all Bilophila strains during the first 24 hours, bactericidal activity was variable; only metronidazole was uniformly bactericidal. Most strains of Bilophila showed 1-2 log increases in gr owth at 6 hours with clindamycin and chloramphenicol. With chloramphen icol, some Bilophila strains tested showed regrowth starting at 30 hou rs. B. gracilis strains were generally more susceptible to all agents tested. Metronidazole, ticarcillin/clavulanate, chloramphenicol, and i mipenem were most active. Several strains of B. gracilis were not kill ed by ampicillin/sulbactam, clindamycin, or cefoxitin. Activity was va riable among strains and antimicrobial agents.