[Sensitivity of anaerobes to 8 antibiotics]

We studied the susceptibility of 282 obligate anaerobes to 8 antibiotics. The strains were isolated from clinical specimens taken during 1983 and 1984. Minimal inhibitory concentrations (MICs) were determined using a microplate method for 245 strains and agar dilution for 33 Bacteroides asaccharolyticus strains. Tested strains were as follows: 85 Bacteroides fragilis, 71 Clostridium, 19 Fusobacterium nucleatum, 35 Peptostreptococcus, 39 Bacteroides oralis and Bacteroides bivius and 33 Bacteroides asaccharolyticus. Tested antibiotics were: metronidazole, clindamycin, minocycline, cefoxitin, cefotaxime, moxalactam, keflin and carbenicillin. For Bacteroides fragilis, the three most active antibiotics were metronidazole (inhibition of all strains with 8 micrograms/ml), minocycline and clindamycin (inhibition of 95% of strains by MICs less than or equal to 0.5 microgram/ml). However, four strains were resistant to clindamycin (MICs greater than 8 micrograms/ml). The other anaerobic strains tested were susceptible. However, a few Bacteroides bivius strains were resistant to keflin (MIC greater than or equal to 64 micrograms/ml for 5% of strains).