4-Year Study in Monitoring the Presence of Legionella in the Campania Region’s Healthcare Facilities

<i>Legionella</i> bacterium has the aquatic environment as its natural reservoir. In humans, it can cause a form of interstitial pneumonia called legionellosis which can be transmitted by inhalation of contaminated water aerosols. <i>Legionella</i> infection occurs more frequently in certain more susceptible population groups, including smokers, alcoholics, men, the elderly, as well as people with acquired immunodeficiency syndrome, hematological cancers, and diabetes mellitus. This study aimed to evaluate the effectiveness of the new Italian National Guidelines for the prevention of <i>Legionella</i> colonization in water systems application by analyzing the environmental monitoring data of <i>Legionella</i> carried out in healthcare facilities in the Campania region from 2019 to 2022. The secondary objectives were to estimate the most observed serogroups of <i>L. pneumophila</i> and to analyze the possible link between water temperature and the presence of <i>Legionella</i>, respectively. From our data, it emerged that in 2019, 41.1% of the examined facilities were contaminated by the <i>Legionella</i> genus; in 2020, the contamination percentage was 42.9%; in 2021, it was 54.5%; in 2022, it was 45.5%. Instead, the <i>Legionella</i> positivity rate decreased from 2019 (54.3%) to 2022 (52.4%), suggesting a possible positive influence of more restrictive prevention and control measures. The prevalent species was <i>Legionella pneumophila</i>, particularly serogroup 1; water temperature was the risk factor implicated in <i>Legionella</i> contamination.