**Intracellular Behaviour of Three** *Legionella pneumophila* **Strains within Three Amoeba Strains, Including** *Willaertia magna* **C2c Maky**

**Issam Hasni 1,2, Antoine Jarry 2, Benjamin Quelard 2, Antoine Carlino 2, Jean-Baptiste Eberst 2, Olivier Abbe 2 and Sandrine Demanèche 2,\***


Received: 10 January 2020; Accepted: 5 February 2020; Published: 6 February 2020

**Abstract:** *Legionella pneumophila* is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as *Acanthamoeba castellanii*. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species support the growth of *L. pneumophila*. *Willaertia magna* C2c Maky, a non-pathogenic amoeba, was previously demonstrated to possess the ability to eliminate the *L. pneumophila* strain Paris. Here, we study the intracellular behaviour of three *L. pneumophila* strains (Paris, Philadelphia, and Lens) within *W. magna* C2c Maky and compare this strain to *A. castellanii* and *W. magna* Z503, which are used as controls. We observe the intracellular growth of strain Lens within *W. magna* Z503 and *A. castellanii* at 22 ◦C and 37 ◦C. Strain Paris grows within *A. castellanii* at any temperature, while it only grows at 22 ◦C within *W. magna* Z503. Strain Philadelphia proliferates only within *A. castellanii* at 37 ◦C. Within *W. magna* C2c Maky, none of the three legionella strains exhibit intracellular growth. Additionally, the ability of *W. magna* C2c Maky to decrease the number of internalized *L. pneumophila* is confirmed. These results support the idea that *W. magna* C2c Maky possesses unique behaviour in regard to *L. pneumophila* strains.

**Keywords:** free-living amoebae; *Legionella*; biological biocide; cooling towers
