[A study on the endotoxin and bacterial contamination in reverse osmosis water and dialysis fluids]

To evaluate the endotoxin (ET) and the bacterial contamination in reverse osmosis (RO) water and dialysis fluids for hemodialysis treatment.

Specimens of RO water and dialysis fluids were obtained at random from 18 hospitals in Beijing. ET was measured with chromogenic limulus amoeboeyte lysate (LAL) assay. Bacteriologic samples were processed on heterotrophic plate count agar with pour plate technique. The plasma IL-1, IL-6 and TNFalpha were tested with enzyme-linked immunosorbent assay (ELISA).

The level of ET in RO water was 0.116 +/- 0.063 EU/ml, and the culture of bacteria had 2 positive results, both counting 100 CFU/ml. The level of ET was much higher in acid concentrate (Protocol B) than in basic concentrate (Protocol A). The culture of bacteria had 11 positive results in Protocol B concentration with 8 samples equal or higher than 2,000 CFU/ml. The culture of bacteria had only 3 positive results in Protocol A concentration, all being lower than 2,000 CFU/ml. Another investigation showed that the level of ET in dialysis inlet was higher than 0.5 EU/ml in 5 cases of a total of 16. Their plasma IL-1 and TNFalpha levels were significantly increased.

Both ET and bacterial contamination exist in RO water and dialysate. It is essential to examine the level of ET and perform bacterial culture, as well as to disinfect RO and dialysate tank at regular intervals in order to reduce pyrogenic reactions.