MONITORING LEGIONELLA PNEUMOPHILA IN DRINKING WATER DISTRIBUTION SYSTEMS IN SOUTHERN CROATIA

In drinking water distribution systems (DWDSs) opportunistic bacteria of environmental origin such as Legionella pneumophila (L. pneumophila) represent a potential source of water contamination, resulting in a potential health risk for humans. The main objective of this study includes an integrated approach based on hazard assessment, identification and monitoring of control factors in order to characterize the influence of physical-chemical parameters on L. pneumophila presence in DWDSs as well as to determine possible seasonal effects, with the purpose of improving the prevention measures. The contamination of hot water samples with L. pneumophila was studied in relation to temperature, pH, free residual chlorine, and metal ions concentrations (iron, copper, zinc, manganese, calcium, and magnesium). The results of microbiological and physical-chemical characteristics were analyzed in order to identify the factors that can effectively contribute to reduce legionellae proliferation and risk of human infection. The samples were collected between March 2009 and December 2011 from three hotels and two homes for the elderly and disabled in the Split-Dalmatian County, Croatia. Legionella pneumophila was isolated in 99 out of 304 samples (32.6%). The seasonal L. pneumophila occurrence trends in drinking water distribution systems were observed, with the highest positive samples percentage of 43.5% found within the 3 super(rd) quarter (7-9 month). L. pneumophila contamination was found to be positively associated with Ca, Mg, Fe and Cu concentrations, and negatively associated with Mn concentrations and temperature.