3 INFEKTOL GLASN 2021;41(1):3-7 https://doi.org/10.37797/ig.41.1.1 Preventing Healthcare-Associated Legionellosis with Rapid Reduction of High Concentrations of Legionella Using Mechanical Removal of Blind Ends and Intensive Hot Water Flushing Sprječavanje legioneloza povezanih sa zdravstvenim sustavom brzim smanjenjem visoke koncentracije legionela uz pomoć mehaničkog uklanjanja slijepih završetaka i ispiranjem vrućom vodom Alan Medić 1 , Anamarija Jurčev-Savičević 2 , Boris Dželalija 3,4 , Dinko Puntarić 5 , Ines Leto 3,4 , Ivanka Matas 6 , Ljilja Balorda 7 1 Department of Epidemiology, Zadar Institute of Public Health, 23000 Zadar, Croatia 2 Teaching Public Health Institute of Split and Dalmatia County, 21000 Split, Croatia; University Department of Health Studies, University of Split, 21000 Split, Croatia 3 Department of Health Studies, University of Zadar, 23000 Zadar, Croatia 4 Department of Infectious Diseases, Zadar General Hospital, 23000 Zadar, Croatia 5 Zagreb Institute of Public Health, 10000 Zagreb, Croatia 6 Department of Microbiology and Parasitology, Zadar Institute of Public Health, 23000 Zadar, Croatia 7 Department of Public Health, Zadar Institute of Public Health, 23000 Zadar, Croatia Abstract Background: The aim of this paper was to present the efectiveness of the mechanical removal of blind ends and fushing of hot water systems at outlets as the only possible emergency measures to reduce the concentration of Legionella spp in hot water. Methods: Two measures have been undertaken: mechanical removal of blind ends and intensive hot water fushing when the water has not been used for more than 7 days. Results: We detected Legionella pneumophila serogroup 1 in concentration of 1.000- 55.000 CFU/L at all samples sites. In the control sampling, after three weeks, we found seven sampling sites negative for Legionella and only two sampling sites positive. All nine sampling sites were negative after ten weeks. Conclusion: Establishing good water fow throughout the hospital seems to be the most important measure, in order to make the multiplication of Legionella in the hot water distribution systems unlikely. Sažetak Cilj: Cilj rada je prikazati učinkovitost mehaničkog uklanjanja slijepih završetaka te ispiranja izljevnih mjesta u sustavu vrućom vodom kao jedinih mogućih hitnih mjera za smanjenje koncentracije Legionella spp u vrućoj vodi. Metode: Poduzete su dvije mjere: mehaničko uklanjanje slijepih završetaka u sustavu te intenzivno ispiranje vrućom vodom u slučajevima kada se voda nije koristila duže od 7 dana. Rezultati: Legionella pneumophila serogrupe 1 u koncentraciji od 1.000- 55.000 CFU/L izolirana je u svim uzor- cima. Kontrolno uzorkovanje nakon tri tjedna pokazalo je sedam mjesta uzorkovanja negativna na bakteriju Legi- onella, a samo dva mjesta su bila pozitivna. Svih devet mjesta uzorkovanja bila su negativna nakon deset tjedana. Zaključak: Uspostavljanje dobrog protoka vode predstavlja najvažniju mjeru za sprječavanje umnožavanja legi- onele u bolničkom sustavima za distribucije tople vode. Keywords: prevention Legionella pneumophila hospital water flow Ključne riječi: prevencija Legionella pneumophila bolnica protok vode Primljeno: 08-09-2020 Received: 08-09-2020 Prihvaćeno: 09-10-2020 Accepted: 09-10-2020 * Corresponding author: Assist. Prof. Alan Medić, MD, PhD, Department of Epidemiology, Zadar Institute of Public Health, Ljudevita Posavskog 7, HR-23000 Zadar, Croatia E-mail: alan.medic@zjz.htnet.hr; Tel.: +385-23-300841; Fax.: +385-23-300844 Izvorni znanstveni rad | Original scientifc paper Introduction Tis paper describes the contamination of the hot water system by Legionella bacteria at the Zadar Gen- eral Hospital (Zadar GH) and the success of emergen- cy measures to reduce their concentration in hospital hot water. Te aim of this paper is to present the efec- tiveness of the mechanical removal of blind ends and fushing of hot water systems at outlets as the only pos- sible emergency measures to reduce the concentration of Legionella spp in hot water.