**Biogeography and Environmental Drivers of** *Legionella pneumophila* **Abundance and Genotype Composition across the West Bank: Relevance of a Genotype-Based Ecology for Understanding** *Legionella* **Occurrence**

#### **Ashraf R. Zayed 1,2, Suha Butmeh 2, Marina Pecellin 1, Alaa Salah 2, Hanna Alalam 2, Michael Steinert 3, Manfred G. Höfle 1, Dina M. Bitar 2 and Ingrid Brettar 1,\***


Received: 15 October 2020; Accepted: 27 November 2020; Published: 1 December 2020

**Abstract:** The West Bank can be considered as a high-risk area for *Legionella* prevalence in drinking water due to high ambient temperature, intermittent water supply, frequent pressure loss, and storage of drinking water in roof containers. To assess occurrence of *Legionella* species, especially *L. pneumophila*, in the drinking water of the West Bank, the drinking water distribution systems of eight hospitals were sampled over a period of 2.3 years covering the seasonal cycle and the major geographic regions. To gain insight into potential environmental drivers, a set of physico-chemical and microbiological parameters was recorded. Sampling included drinking water and biofilm analyzed by culture and PCR-based methods. Cultivation led to the isolation of 180 strains of *L. pneumophila* that were genotyped by Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA). Surprisingly, the abundance of culturable *L. pneumophila* was low in drinking water of the sampling sites, with only three out of eight sites where *Legionella* was observed at all (range: 30–500 CFU/Liter). By contrast, biofilm and PCR-based analyses showed a higher prevalence. Statistical analyses with physico-chemical parameters revealed a decrease of *L. pneumophila* abundance for water and biofilm with increasing magnesium concentrations (>30 mg/L). MLVA-genotype analysis of the *L. pneumophila* isolates and their spatial distribution indicated three niches characterized by distinct physico-chemical parameters and inhabited by specific consortia of genotypes. This study provides novel insights into mechanisms shaping *L. pneumophila* populations and triggering their abundance leading to an understanding of their genotype-specific niches and ecology in support of improved prevention measures.

**Keywords:** MLVA-genotypes; ecotype; groundwater; environmental factors; magnesium; niche
