Microbial and endotoxin contamination in water and dialysate in the central United States

Abstract

The purified water supplies and randomly selected dialysates of 51 chronic and acute dialysis centers in the central United States were surveyed to assess the relative risks to dialysis patients from microbial and endotoxin contamination. A culture medium more sensitive than those generally employed in routine quality assurance assays was used for recovery of bacteria from water. With this medium, 35.3% of the water samples and 19% of the dialysate samples were out of compliance with the Association for the Advancement of Medical Instrumentation (AAMI) standards: 200 and 2,000 colony forming units (CFU)/ml, respectively. There was no correlation observed between the type of water purification system or the frequency of disinfection of the system and the bacterial and endotoxin contamination levels. There was also no correlation found between the bacterial and fungal CFU per ml and the endotoxin concentration per ml (EU/ml). It is recommended that more sensitive culturing methods be used to provide adequate bacterial monitoring of dialysate center water supplies. Dialysis centers should monitor endotoxin in dialysate on a regular schedule and immediately after any endotoxemic-like patient reactions. Yeast and fungi were observed in 10% and 64% of the water systems, respectively. Dialysate was contaminated by yeast and fungi in 30% and 70% of the centers, respectively. The concentrations of these microbes in both fluids were much lower than bacteria. However, they were observed often enough to warrant further investigation of their impact on the well-being of dialysis patients.