Microbiological qualification of air, water and dialysate in a haemodialysis centre: a new focus on Legionella spp.

BACKGROUND AND OBJECTIVES The microbiological monitoring of the water used for haemodialysis is important especially for Legionella and non-fermentative bacteria since patients with end stage renal disease (ESRD) are suffering from deteriorated function of immune system. MATERIALS AND METHODS A total 50 water and dialysate samples were weekly collected over a period of 10 weeks from 5 sites. Total and faecal coliforms were determined by utilizing the most probable number (MPN) method. For isolation of Legionella, water samples were inoculated on a BCYE medium. DNA extraction was performed and was used to amplify 16S rRNA gene of Legionella species. Airborne bacteria were sampled using a single stage Andersen air sampler. RESULTS Out of total 50 water samples, 24 samples had bacterial contamination. The highest rate of Legionella contamination was observed in the storage tank (67 cfu/ml). Legionella was not isolated from the dialysate effluent samples. The highest rate of total bacterial count was related to the dialysate effluent and the maximum total count of coliforms was related to the reverse osmosis. The isolated bacteria were Gram-negative bacilli (mostly Pseudomonas isolates), Gram-positive cocci (mostly Micrococcus spp.) and Gram-positive bacilli (mostly Bacillus spp.). Six samples were contaminated with coliforms. No faecal coliform was isolated from the samples. CONCLUSION These results indicated that dialysis machine is an important source of contaminations such as Staphylococcus, Pseudomonas and Legionella. Therefore an efficient prevention program is needed to eliminate bacterial contamination of dialysis water system. Moreover, in haemodialysis centres, periodic surveillance programs for microbiological qualification can lead to a better planning for disinfection of haemodialysis water systems.