[Susceptibility of clinically important Bacteroides species against enoxacin-metronidazole and enoxacin-clindamycin combinations].

To assess the activity of enoxacin, clindamycin and metronidazole, MICs of clinical isolates of saccharolytic intestinal Bacteroides spp. were determined, using the agar dilution method according to NCCLS guidelines. Checkerboard titrations of enoxacin-metronidazole and enoxacin-clindamycin were done on Wilkins-Chalgren agar; inoculation, incubation and reading of plates were as for determination of MICs. Metronidazole MIC 90s for Bacteroides fragilis (23 strains) and Bacteroides thetaiotaomicron (23 strains) were 0.5 mg/l, clindamycin MIC 90 for B. fragilis was 1 mg/l, and for B. thetaiotaomicron 8 mg/l, whereas enoxacin MIC 90 values were 16 mg/l and 64 mg/l, respectively. The evaluation of the inhibitory effects of the combination enoxacin-metronidazole for B. fragilis showed additional effects in eleven strains, indifference in seven strains and antagonism in one. The figures for B. thetaiotaomicron showed addition in five strains, indifference in 17 strains, antagonism in one. For B. fragilis the combination enoxacin-clindamycin showed addition in ten strains, indifference in six, and antagonism in one; for B. thetaiotaomicron synergism in one strain, addition in four strains, indifference in 17 strains. In conclusion, the absence of antagonism and the overall preponderance of additional and indifferent effects warrant the use of enoxacin in combination with metronidazole or clindamycin in clinical trials of treatment of anaerobic-aerobic mixed infections.