Efficacy of chlorine dioxide disinfection to non-fermentative Gram-negative bacilli and non-tuberculous mycobacteria in a hospital water system

Summary Background Chlorinated tap water in hospitals often contains low levels of non-fermentative Gram-negative bacilli (NFGNB) and non-tuberculous mycobacteria (NTM). Measures are needed to ensure a safe water supply in hospitals to prevent nosocomial infections from these waterborne pathogens. Aim To evaluate the efficacy of ClO 2 treatment of a hospital water system on the levels of NFGNB and NTM in the water. Methods Our institution is a 1000-bed medical centre with two main buildings (B1 and B2). B1 has three intensive care units (ICUs) and transplant wards and polyethylene water pipes. B2 (control) has no ICUs and galvanized water pipes. A ClO 2 generating unit was installed in the water system of B1 in April 2012 and water samples were collected in B1 and B2 before and eight times after installation. All samples were cultured for NFGNB and NTM. Findings The ClO 2 concentration was significantly lower in the hot water than in the cold water ( P 2 use, the overall NFGNB colonies decreased significantly (hot water: 160±143 vs 2±4cfu/mL, P P Pseudomonas spp. and Stenotrophomonas spp., were undetected three months after ClO 2 disinfection; Sphingomonas spp. persisted but had lower colony counts. NTM was present in 25% (three out of 12) of sampling locations initially, but was not detected at two weeks after ClO 2 disinfection. The ICUs had no overall change in the number of NFGNB nosocomial infections after the intervention. Conclusion Addition of a ClO 2 disinfection unit to our hospital water system reduced the numbers of NTM and NFGNB in the hot and cold water systems.