Background: Bacterial contamination of treated water and dialysate comprises an important problem for patients undergoing haemodialysis. Both the progressive reduction of the thickness of cellulose membranes and the expanding use of high-flux membranes probably enhance the risk of pyrogenic reactions, therefore increasing the need for atoxic water and non-pyrogenic dialysis fluid.
Methods: Samples of tap water, treated water, and effluent dialysate in all 85 haemodialysis centres in Greece were examined for total heterotrophic bacteria counts employing the pour plate method, total and faecal coliforms, faecal streptococci and pseudomonas spp. using the membrane filter technique, and sulphite-reducing clostridia applying the most probable number method. Overall 255 paired samples were tested from January to March 1997.
Results: For total heterotrophic bacteria, the overall compliance of treated water and dialysate to the American Association of Medical Instrumentation standards (<200 c.f.u./ml for water and <2000 c.f.u./ml for dialysate) was 92.6 and 63.7% respectively, whereas the compliance of tap water samples to our national standards (total heterotrophic bacteria < 10 c.f.u./ml and absence of the other indicator bacteria) was 80.7%. The most commonly isolated bacteria were pseudomonas spp., found in 22.2% of treated water and 59.5% of dialysate samples, whereas the respective frequencies were 12.3 and 36.2% for total coliforms, 8.6 and 30.0% for faecal coliforms, 14.8 and 28.7% for faecal streptococci, and sulphite-reducing clostridia were isolated in 5.8% of dialysate samples only. Haemodialysis centres equipped with storage tanks for treated water experienced lower levels of total heterotrophic bacteria, but higher counts of total and faecal coliforms, faecal streptococci, and pseudomonas spp., although the difference was statistically significant only for faecal streptococci counts, (P<0.05). Sixty-seven haemodialysis centres were equipped with bacterial filters, but mean values of all the examined microorganisms were not statistically different from those of the other centres. Faecal streptococci counts in treated water samples were positively correlated with ageing of both haemodialysis centres (P<0.005) and purification system (P<0.05), whereas pseudomonas counts were significantly correlated with ageing of the purification system (P<0.05).