Legionella control in a tertiary care hospital in Italy: adapting solutions to changing scenarios

Abstract

Abstract Background Legionella contamination of hospital water distribution system still remains a critical issue in healthcare settings, despite the disputed relationship between environmental legionella and hospital-acquired legionellosis. We report the experience of our 1200-beds hospital, where a new water safety plan (WSP) has been applied since 2017, and the results obtained with the application of different methods to control Legionella water contamination, especially in critical areas. Methods Policlinico San Martino is the referral tertiary acute-care university hospital in Liguria region, North-West Italy. It’s made of 21 buildings of different dimensions, 7 of which host high risk patients, according to Italian Guidelines for legionellosis prevention and control. A sampling plan for Legionella detection was implemented in 2017, focusing on the water network critical points. Different secondary disinfection procedures were used, including systemic (chlorine dioxide, monochloramine), focal (point-of-use filtration) and short-term methods (hyperchlorination), the last in case of contamination higher than 10^4 CFU/l. Results Respectively, during 2017 and 2018 a total of 201 and 119 hot water samples were collected, distributed among the 7 critical buildings of the hospital. Negative samples raised from 69.7% to 74.8%, while positive samples >10^3 CFU/l (recommended cut-off for acute disinfection according to Italian guidelines) lowered from 21.9% to 9.2% of total samples. Out of 55 positive samples, Legionella sg 3 accounted for 98.2% of the total. Conclusions The new WSP determined a significant reduction of Legionella contamination of water distribution networks in our hospital critical buildings. The continuous surveillance of critical water system points provided evidence to elaborate an effective protocol for routine and extraordinary disinfection interventions, as result of a close collaboration between hospital hygiene unit and engineering and technical services. Key messages The implementation of an effective water safety plan and different disinfection procedures in hospital critical areas allow us to reduce and control the risk of hospital-acquired Legionella infection. Continuous surveillance cultures of drinking water to detect Legionella are necessary to adapt disinfection methods to local results.