Recovery of S. epidermidis and E. coli from effluent peritoneal dialysate

The effect of incubation temperature and duration was studied on the growth of organisms in peritoneal dialysate effluent. Penicillin-sensitive, and gentamicin-sensitive clinical isolates of S. epidermidis (SE) and E. Coli (EC), respectively, were inoculated into freshly drained dialysate of 19 CAPD patients who did not have peritonitis. Each dialysate was 1.5% dextrose in strength and had a minimum dwell of 6 hours. Control and test aliquots were incubated at 4 degrees C, 20 degrees C and 37 degrees C for periods of up to 12 hours, and samples collected and plated to determine colony counts. Initial counts at time zero were 9.4 x 10(4) (SE) and 6.6 x 10(3) (EC) CFU/ml. SE showed no change in count at 4 or 20 degrees C up to 12 hours. There was a significant increase (p less than 0.005) at 37 degrees C, at 12 hours to 1.72 x 10(6) CFU/ml. EC showed no change at 4 or 20 degrees C. There was a significant decrease in count for EC at 37 degrees C, 6 hours (5.5 x 10(2) CFU/ml, p less than 0.01) and 37 degrees, 12 hours (2.9 x 10(2) CFU/ml, p less than 0.0001). It is recommended that infected dialysate should be stored in cool conditions until it can be transported for culture to ensure adequate recovery of gram negative organisms.