Four-Year Environmental Surveillance Program of Legionella spp. in One of Palermo's Largest Hospitals

Abstract

Legionella is a ubiquitous bacterium that lives in freshwater environments and colonizes human-made water systems. Legionella pneumophila is the most virulent species, and risk factors for Legionnaires' disease include increasing age, smoking, chronic diseases, and immunodeficiency. For this reason, it is very important to assess and monitor hospital water systems in order to prevent legionellosis. We have monitored a large hospital in Palermo for four years. To determine the presence of microorganisms, according to national guidelines, we used the culture method, which is considered the gold standard for Legionella detection. Sampling was divided into five macro-areas, and a total of 251 samples were collected during the period of investigation, 49% of which were Legionella spp.-positive and 51% were Legionella spp.-negative. Positive samples with L. pneumophila. sgr 2-15 were most frequent in the Underground (55.6%, p = 0.0184), Medicine (42.9%, p = 0.0184) and Other (63.2%, p = 0.002) areas; while positive samples for L. pneumophila sgr 1 were less frequent in the Underground (0.0%, p = 0.0184) and Surgery areas (4.5%, p = 0.033), and for Legionella anisa, were less frequent in the Medicine (4.1%, p = 0.021), Oncohematology (0.0%, p = 0.0282), and Other (0.0%, p = 0.016) areas. Finally, no significant differences were observed among the areas for each isolate considered. The surveillance carried out in these years demonstrates the importance of monitoring, which allows us to analyze the conditions of hospital facilities and, therefore, prevent Legionella spp. infections.

Keywords: Legionella; hospital; surveillance; water system.

Figure 1

Total number of positive samples related to the bacterial load of L. pneumophila. and L. anisa isolates. For each of the three clusterings (L. pneumophila sgr 1, L. pneumophila sgr 2-15, L. anisa), the greatest number of positive samples had a load within the lowest range, the value of which has been established by Italian ministerial guidelines.

Figure 2

Trend recorded on a yearly basis during the four-year surveillance program reporting the number of positive isolates for L. pneumophila serogroups and L. anisa.

Figure 3

Number of samples with presence of co-isolates during the four-year surveillance program, regarding different L. pneumophila (L.p.) sgrs and L. anisa.