Bactericidal activity of peritoneal macrophages from continuous ambulatory dialysis patients.

A radiometric assay is described for measuring phagocytosis and intracellular killing of Staphylococcus epidermidis by peritoneal cells from continuous ambulatory peritoneal dialysis (CAPD) patients. Using this method it is possible to determine simultaneously and independently, in a single assay, whether peritoneal cells from CAPD patients possess defects in either ingestion or intracellular killing. Assays were performed on peritoneal cells obtained from 28 samples of spent dialysis fluid from CAPD patients. In the majority of cases these cells were able to efficiently phagocytose and kill opsonised Staph. epidermidis, although the degree of intracellular killing was slightly reduced compared with peritoneal cells obtained from eight normal controls undergoing laparoscopy. Overall there was no correlation between the degree of phagocytosis or intracellular killing and susceptibility of patients to peritonitis, although cells from two patients with a high incidence of peritonitis did show abnormally poor ingestion and/or killing. In a number of samples only low numbers of cells (less than 10(6)) were recovered in total from the overnight bags, and there was a significant inverse correlation between the number of cells in the fluid and the length of time on CAPD.