Intracellular Behaviour of Legionella Non-pneumophila Strains within Three Amoeba Strains, Including Willaertia magna...

Area of Science:

• Environmental microbiology
• Infectious diseases
• Bacterial pathogenesis

Background:

• Legionellosis, a severe pneumonia, is primarily linked to *Legionella pneumophila*.
• Legionella bacteria can survive in amoebae, hindering eradication efforts.
• Emerging evidence suggests other *Legionella* species also cause Legionellosis.

Purpose of the Study:

• To investigate the interaction between *Legionella* non-pneumophila (Lnp) strains and amoebae.
• To determine if Lnp strains can replicate within amoebae.
• To assess the amoebae's ability to control Lnp proliferation.

Main Methods:

• Co-culturing seven Lnp strains (*L. longbeachae*, *L. anisa*, *L. bozemanae*, *L. taurinensis*, *L. dumoffii*) with three amoebae (*Acanthamoeba castellanii*, *Willaertia magna* T5(S)44, *Willaertia magna* C2c Maky).
• Incubation at two temperatures: 22 °C and 37 °C.
• Microscopic observation and analysis of bacterial intracellular survival and replication.

Main Results:

• At 22 °C, amoebae phagocytosed all Lnp strains but generally prevented intracellular multiplication, with *L. longbeachae* being an exception inside *W. magna* T5(S)44.
• At 37 °C, four Lnp strains successfully replicated within one or two amoebae species.
• No Lnp strains were found to multiply within *Willaertia magna* C2c Maky at 37 °C.

Conclusions:

• Specific *Legionella* non-pneumophila species can exploit amoebae for intracellular proliferation, particularly at human body temperature (37 °C).
• Amoebae species exhibit varying capacities to control Lnp growth, indicating complex host-pathogen interactions.
• These findings highlight the role of non-pneumophila *Legionella* in Legionellosis and the importance of amoebae as reservoirs.