<i>Legionella</i> spp. in Polish hospitals in 2009–2013 and 2014–2016: An epidemiological analysis

Summary Introduction Bacteria of the genus Legionella cause Legionnaires’ disease (atypical pneumonia, often with a severe clinical course) and Pontiac fever (self-limiting infection with flu-like symptoms). Legionella spp. are commonly found in natural aquatic environments and artificial water distribution systems. Material &amp; Methods An epidemiological analysis of Legionella spp. in hospital water supply systems was based on the results obtained from Sanitary-Epidemiological Stations of Poland. The materials for this study were hot water samples collected from 346 hospitals in 2009–2013 and from 221 hospitals in 2014–2016. Results Between 2014 and 2016, there was a decrease in the percentage of the number of water samples in Group A (&lt;100 CFU/100 ml). In other groups: B (&gt;100 CFU/100 ml), C (&gt;1000 CFU/100 ml), D (&gt;10 000 CFU/100 ml) was observed an increase in the percentage of the number of water samples, which was a negative phenomenon. The mean number of L. pneumophila colonies in analyzed periods 2009–2013 and 2014–2016 were different. In 2009–2013, the most virulent L. pneumophila serogroup 1 (SG 1) was detected in 3 hospitals (0.9%), and L. pneumophila SG 2-14 were isolated in 20 (5.5%). Between 2014 and 2016, L. pneumophila SG 1 and L. pneumophila SG 2-14 were found in 5 hospitals (2.2%) and 18 hospitals (8.1%), respectively. Disscusion In this study a comparative epidemiological analysis was performed on the prevalence of L. pneumophila in hospital water supply systems in Poland in the following two periods: 2009 –2013 and 2014–2016. The study demonstrated that the water supply systems of Polish hospitals were colonized by L. pneumophila at different levels. However, between 2014 and 2016 an upward trend was observed in comparison with 2009–2013.