Experimental pneumonitis induced by Naegleria fowleri in mice

Area of Science:

• Environmental microbiology
• Pathogen research
• Infectious diseases

Background:

• Naegleria fowleri is a free-living amoeba known to cause primary amoebic meningoencephalitis (PAM).
• Environmental conditions, such as thermal additions from power plants, may influence the presence and pathogenicity of Naegleria species.

Purpose of the Study:

• To investigate the pathogenicity of an environmental Naegleria isolate from a thermally altered cooling lake.
• To determine if the isolate could cause infections beyond the central nervous system in a murine model.

Main Methods:

• Intranasal inoculation of mice with an environmental Naegleria isolate.
• Recovery and re-isolation of amoebae from infected mouse tissues (brain and lungs).
• Histopathological examination of infected lungs using electron microscopy.
• Serological identification of re-isolated amoebae using indirect immuno-fluorescent antibody technique.

Main Results:

• The environmental Naegleria isolate successfully induced both primary amoebic meningoencephalitis (PAM) and pneumonitis in mice.
• Amoebae were consistently re-isolated from the brains and lungs of infected mice across multiple passages.
• Electron microscopy revealed moderate inflammation and slight necrosis in infected lung tissues.
• Re-isolated amoebae were confirmed as Naegleria fowleri using specific antibodies.

Conclusions:

• The environmental Naegleria isolate is pathogenic and capable of causing both neurological and pulmonary infections in mice.
• Naegleria fowleri may be implicated in causing subacute and acute respiratory infections in humans, in addition to PAM.
• Thermally influenced aquatic environments may harbor pathogenic Naegleria fowleri strains with broader infectious potential.