Effect of clindamycin on the intracellular bactericidal capacity of human peritoneal macrophages

Abstract

Survival and growth of bacteria within peritoneal macrophages has been implicated as a cause of recurrence and relapse of Staphylococcus epidermidis peritonitis during peritoneal dialysis. We studied the effect of orally administered clindamycin (known to enter and concentrate in phagocytes) on the intracellular killing of S. epidermidis by human peritoneal macrophages. Clindamycin (300 mg qid) was taken for one day by eight CAPD patients. Peritoneal macrophages were isolated from the effluents and their capacity to phagocytose and kill S. epidermidis was measured. In effluents containing clindamycin, the macrophages showed better uptake (32 vs 17%, P less than 0.01) and intracellular killing (70 vs 42%, P less than 0.01) of S. epidermidis compared with control after 1 h incubation. After 18 h S. epidermidis within peritoneal macrophages incubated with clindamycin, showed a further decrease in viability (-0.33 decrease in log cfu/ml). In contrast, control phagocytes allowed numbers of S. epidermidis to increase over 18 h (+1.46 increase in log cfu/ml; P less than 0.01 compared to clindamycin). Antibiotics with the ability to suppress intracellular bacterial growth should be studied for treatment of CAPD-related S. epidermidis peritonitis.