Effects of metal corrosion in the pump of a dialysis machine on the sterility of the terminal dialysate by spike-and-recovery testing with bacteria

Background Dialysis units have been concerned that the corroded metal parts of pumps used in hemodialysis might not allow sterility of the pump to be ensured due to bacterial contamination, even after cleaning and disinfection are performed after dialysis treatment. The purpose of this study was to clarify the effectiveness of the cleaning/disinfection process in eliminating bacterial contamination of the dialysate in pumps with and without metal corrosion. Methods A suspension of Pseudomonas aeruginosa [10 colony-forming unit (CFU)/mL] was introduced into pumps without or with corrosion of the metal parts, and the flow in the dialysis circuit was stopped for 6, 12, or 18 h. Then, after cleaning and disinfection of the circuit with a sodium-hypochlorite-containing reagent, the amounts of live bacteria in the terminal dialysate and on the surface of the metal parts of the pump were counted. Results Irrespective of the presence or absence of metal corrosion, bacteria were detected, even after cleaning and disinfection, on the surfaces of the pump parts that had been left in contact with the bacterial suspension for more than 12 h. However, on the surfaces of the pump parts showing metal corrosion, the bacterial numbers increased dramatically after 18 h of flow stoppage time following introduction of bacteria, and bacteria were even detected in the terminal dialysate despite cleaning/disinfection of the pump. Conclusions Corrosion of the metal parts used in pumps used for dialysis increases the risk of bacterial contamination of not only the pump parts and flow path of the dialysis machine but also the terminal dialysate, even if cleaning/disinfection is performed. For sterility assurance of the dialysis circuit and dialysate during routine use, it is necessary to eliminate corrosion of the metal parts of dialysis pumps during scheduled maintenance.