**A Snapshot of the Prevalence and Molecular Diversity of** *Legionella pneumophila* **in the Water Systems of Israeli Hotels**

**Eugenia Yakunin 1, Eszter Kostyal 2, Vered Agmon 1, Itamar Grotto 1,3, Lea Valinsky 1 and Jacob Moran-Gilad 1,3,\***


Received: 20 April 2020; Accepted: 23 May 2020; Published: 27 May 2020

**Abstract:** Exposure to *Legionella* spp. contaminated aerosols in hotel settings confers risk for travel-associated Legionnaire's disease (TALD). In this study, we investigated the prevalence of *Legionella* contamination and its molecular diversity in hotels and resorts across Israel. The study was comprised of a convenience sample of water systems from 168 hotels and resorts countrywide, routinely inspected between March 2015 and February 2017. Isolation and quantitation of *Legionella* were performed in a water laboratory using the ISO 11731 method. The distribution of *Legionella* isolates was analyzed according to geography and source. The genetic diversity of a subset of isolates was analyzed by sequence-based typing (SBT) at the National Reference Laboratory for *Legionella* and compared to the national database. Out of 2830 samples tested, 470 (17%) obtained from 102 different premises (60% of hotels) were positive for *Legionella* spp. In 230 samples (49% of all positive, 8% of total samples), accounting for 37% of hotels, *Legionella* spp. counts exceeded the regulatory threshold of 1000 CFU/L. The most frequently contaminated water sources were cooling towers (38%), followed by faucets, hot tubs, water lines, and storage tanks (14–17% each). Furthermore, 32% and 17% of samples obtained from cooling towers and hot tubs, respectively, exceeded the regulatory thresholds. SBT was performed on 78 strains and revealed 27 different sequence types (STs), including two novel STs. The most prevalent STs found were ST1 (26%), ST87 (10%), ST93 (6%), and ST461 and ST1516 (5% each). Several *L. pneumophila* STs were found to be limited to certain geographical regions. This is the first study to investigate the prevalence and diversity of *Legionella* in hotels and resorts in Israel during non-outbreak environmental inspections. These findings will inform risk assessment, surveillance, and control measures of TALD.

**Keywords:** *Legionella pneumophila*; SBT; molecular diversity; hotels
