Bacterial DNA in water and dialysate: detection and significance for patient outcomes

The fluid used for hemodialysis may contain DNA fragments from bacteria, which could be harmful for patient outcomes. DNA fragments from bacteria, containing the nonmethylated CpG motif, can trigger inflammation through the monocyte and lymphocyte Toll-like receptor 9, and these DNA fragments have been observed in dialysate. The fragments may transfer across the dialyzer into the patient's bloodstream during hemodialysis treatment. During hemodiafiltration, the fragments would be introduced directly into the bloodstream. The DNA fragments may arise from biofilm in the pipes of the water system, from growth of bacteria in the water, or as contaminants in the bicarbonate and salt mixture used for preparation of dialysate. Current filtration methods, such as Diasafe filters, are not able to remove these fragments. It would be prudent to seek to reduce or eliminate these contaminants. However, the cost and effort of decreasing bacterial DNA content may ultimately require substantial facility improvements; we therefore need to fund research studies to determine if modifications to reduce bacterial DNA content are clinically warranted. This research will require methods to accurately determine the species of bacteria that contribute the DNA, since this information will allow the source to be established as biofilm, bicarbonate mixtures, or other problems in the dialysis system such as bacterial growth or leakage during water preparation. In this review, the evidence for bacterial DNA fragments will be examined and suggestions for further studies will be described.