Bacterial Contamination and Endotoxin Production in the Water Treatment System for Hemodialysis

ABSTRACT
Background: Dead spaces and connections between units (segments) of fluid production and delivery in elder system are a continuous source for bacterial growth, biofilm generation and endotoxin release. The role of bacterial contamination of dialysis water with respect to chronic inflammatory diseases  associated with long-term hemodialysis (HD) therapy has been greatly underestimated. Pyrogenic substance of bacterial origin derived from contamination dialysate penetrate intact dialyzer membranes with the consequence of the induction of an inflammatory response in the patient.
Objectives: The present study aimed to assess bacterial contamination and endotoxin production in the water treatment system for HD. It also aimed to evaluate the efficiency of decontamination measures applied along the water pathway in the system.
Methods: The study was conducted in the water treatment system of the Pediatric Dialysis Unit. Children′s Hospital, Ain Shams University. Samples were examined for four consecutive weeks after changing the bacterial filter; each week three samples were collected. One sample was taken from tap water (sample A), another sample was taken from treated water just after the bacterial filter (sample B) and the third sample was taken from water in the returning pipe system not used by the hemodialysis machines (sample C). Quantitative methods were used for the total count of viable heterotrophic microorganisms (denoting bacterial contamination), total coliforms, enterococci, Pseudomonas spp. And the sulfite-reducing clostridia (denoting fecal contamination). The samples were assayed for endotoxin by Limulus Amebocyte Lysate (LAL) kit employing a GEL-CLOT LAL. It is a qualitative non-kinetic assay.
Results: The results of the study showed that the methods of decontamination used in the water treatment system are efficient in decreasing the counts of all types of bacterial studied compared to tap water (sample A) with nearly equal efficiency for all types of bacteria. Also, the passage of water in the pipe system of the HD unit to all dialysis machines did not affect its state concerning bacterial contamination as evidenced by the absence of rise in bacterial counts in sample C. Pseudomonas spp. Did not show any growth on its specific medium although the study. It was also noted that the efficiency of decontamination methods used-particularly the bacterial filter – is affected by time as evidence by the rise in bacterial counts in sample B over the 4 weeks of the study to become nearly totally inefficient after 4 weeks. Concerning endotoxin. It is positive although the study denoting complete inefficiency of the decontamination methods used in getting rid of endotoxin.
Conclusions: Tap water was heavily contaminated with heterotropic bacteria, fecal coliforms, enterococci, sulfite-reducing bacteria and total coliforms. The antibacterial measures adopted in the unit were not as efficient as expected. However, the method of decontamination used for the pipe system was efficient. Endotoxin was detected in all water samples. Recommendation : in order to improve the antibacterial measures used in the water treatment system of the HD unit under study, it is recommended to change the bacterial filter used more frequently or to use more recent bacterial filters. Regular bimonthly disinfection of the whole water treatment system (pre and post RO) utilizing the same disinfectants currently used that proved to be efficient in the post RO section is also recommended. Concerning endotoxin, it is expected that the better decontamination of the system might reduce the load of endotoxin, but the only specific solution-although financially difficult  - is the use of poly sulfone water filter that removes endotoxin from water at its entrance to the dialysis machine.