Comparative study of clindamycin, imipenem, oxacillin and vancomycin in the infected granuloma pouch model.

In a rat granuloma pouch model, Staphylococcus aureus infection was treated with clindamycin, oxacillin or vancomycin and Bacteroides fragilis infection with clindamycin or imipenem. The model simulates a subcutaneous abscess and has the advantage of permitting frequent sampling of exudate for bacterial counts and antibiotic levels in the same animal. In staphylococcal infection all drugs reduced the bacterial counts in the infected pouch by 1-1.7 log, with a significant effect lasting for 3 h after the last injection. A 1.06-1.4 log reduction lasted for 24 h with clindamycin and oxacillin, but there was only an 0.3 log reduction at 24 h with vancomycin. The ratio of the drug concentration in the infected pouch to the MIC was highest with clindamycin (2.3) compared to oxacillin (1.6) and vancomycin (0.8). With Bact. fragilis infection the bacterial counts dropped 1.5 log at 3 h after the last injection with clindamycin and imipenem. At 24 h the counts were reduced 1.0 log with clindamycin and 0.5 log with imipenem. The ratios of pouch fluid concentration to MIC was 7.6 and 4.08 for imipenem and clindamycin, respectively, at 3 h, and 1.0 and 2.3 for imipenem and clindamycin at 24 h.