FRONT MATTER Title: Presence of Legionella spp. in hot water networks of different Italian residential buildings: a three-year survey

Although the European reports highlight an increase in community-acquired Legionnaires’ disease cases, the risk of Legionella spp. in private houses is underestimated. In Pisa (Italy) we performed a three-year survey on Legionella presence in 121 buildings with an independent hot water production (IB); 64 buildings with a central hot water production (CB); and 35 buildings with a solar thermal system for hot water production (TB). From all the 220 buildings Legionella spp. was researched in two hot water samples collected either at the recirculation point or at on the first floor and on the last floor, while the potable water quality was analyzed in three cold water samples collected at the inlet from the aqueduct network, at the exit from the autoclave, and at the most remove remote? tap. Legionella pneumophila sg1, Legionella pneumophila sg2-16 and not-pneumophila Legionella species were detected in 26% of the hot water networks, mostly in CB and TB. In these buildings we detected correlations between the presence of Legionella and the total chlorine concentration decrease or/and the increase of the temperature. Cold water resulted free from microbiological hazards, with the exception of Serratia liquefaciens and Enterobacter cloacae isolated at the exit from two different autoclaves. We observed an increase in total microbial counts at 22 and 37°C between the samples collected at the most remote taps compared to the ones collected at the inlet from the aqueduct. The study highlights a condition of potential risk for susceptible categories of population and supports the need for measures of risk assessment and control. Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 10 October 2017 doi:10.20944/preprints201710.0058.v1 © 2017 by the author(s). Distributed under a Creative Commons CC BY license. Introduction Legionella spp. is a Gram negative aerobic bacterium, which is widely present in soil and freshwater but that can also contaminate water systems; it replicates between 25°C and 42°C surviving at higher temperatures [1-2]. Legionella infection may cause distinct clinical diseases as Legionnaires’ Disease and Pontiac fever. Infection is acquired by inhalation, aspiration or micro-aspiration of Legionella carrying aerosols. Droplets carrying the pathogen can originate by water spraying or by gurgling air through contaminated water. Immunocompromission, chronic diseases and old age are predisposing factors for the development of the disease [3]. Legionella pneumophila serogroup 1 is the species most commonly associated with the disease. It is the cause of 95% of Legionella infections in Europe and 85% worldwide [4-6]. The surveillance of legionellosis is coordinated in Europe by the European Centre for Disease Prevention and Control (ECDC), and in Italy by the Italian National Institute of Health. The latest data, related to 2015 give 1,553 cases of legionellosis in the Italian population, corresponding to a notification rate of 2.55 cases per million inhabitants. However, it must be noted that 2015 has seen an increase of 5.6% in the cases when compared with the previous year. Of the 1,553 notified cases, 83 (5.3%) were hospital acquired, while 1,221 (78.5%) were community acquired infections, underscoring the relevance of Legionella contamination of community environment and to the subsequent need for control [7-8]. Literature data on Legionella contamination in air conditioning systems and hot water networks are available for hospitals [9-10], but, despite the high percentage of Legionella community acquired infections, few published papers have focused on the presence of Legionella in small residential buildings [11]. In Italy in Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 10 October 2017 doi:10.20944/preprints201710.0058.v1