Effectiveness of a Neutral Electrolysed Oxidising Water (NEOW) Device in Reducing Legionella Pneumophila in a Water Distribution System: A Comparison Between Culture, Qpcr and PMA-qPCR Detection Methods

Disinfection of hot water systems is critical for reducing Legionnaires' disease in high-risk buildings. The use of neutral electrolysed oxidising water (NEOW) is a promising method for the control of microorganisms in hot water systems. However, full-scale evaluations of the efficacy of NEOW devices to control Legionella pneumophila are currently lacking. The aim of this study was to assess the effectiveness of a NEOW device in reducing L. pneumophila in a hotel water network. Water samples (n = 67) were collected from different sites of a hotel distribution system before and after the installation of the NEOW device at the 1st, 4th, 8th and 12th week. Detection of L pneumophila was performed comparing culture, qPCR and PMA-qPCR methods. Total bacterial counts (22 degrees C and 37 degrees C), Pseudomonas spp. and physico-chemical parameters were also monitored. The NEOW treatment resulted in a reduction of the amount of L pneumophila positive samples (-32%) and of the number of heavily contaminated points (>10(4) CFU/L and >10(3) CFU/L) (-100% and -96%, respectively). Treatment maintained L pneumophila at low levels (<10(2) CFU/L), which do not require specific intervention measures. The effectiveness of the disinfection system was also confirmed by PMA-qPCR (p < 0.001). The use of PMA resulted in a signal decrease in almost all samples upon the disinfection treatment. The NEOW disinfection device appears to be a promising approach to reduce the colonisation of hot water systems by L. pneumophila; however, further investigations are needed to ascertain its efficiency over longer time periods. (C) 2018 Elsevier Ltd. All rights reserved.