Pathogenic Free-Living Amoebae and Human Health

Free-living amoebae (FLA) are ubiquitous protozoa in soil and freshwater that can opportunistically infect humans, causing severe diseases with high morbidity and mortality. Chief among these pathogens are Acanthamoeba spp., responsible for sight-threatening corneal infection in contact lens wearers and others, and Naegleria fowleri, the causative agent of rapidly fatal primary amoebic meningoencephalitis (PAM). Disease arises when environmental trophozoites adhere to and invade host tissues, evading innate defences by encystation or secreting cytolytic enzymes. Clinical diagnosis is often delayed by non-specific early symptoms and limited point-of-care tests, contributing to poor outcomes. Conventional antiamebic therapy remains suboptimal, prompting exploration of novel pharmacological agents and delivery systems. In parallel, FLA serve as environmental reservoirs and vectors for diverse intracellular microbes, amplifying public-health risks. Recent research has advanced molecular diagnostics, illuminated mechanisms of host–pathogen interaction and identified promising treatment strategies with global applicability.

Research from Nature Portfolio

Innovative nanoparticle formulations have emerged to target brain-eating amoebae and multidrug-resistant bacteria simultaneously. Green-synthesised silver and gold nanoparticles, stabilised by plant gums and loaded with flavonoids, demonstrated complete amoebicidal activity against Acanthamoeba castellanii and Naegleria fowleri at low micromolar concentrations. These constructs prevented trophozoite proliferation, blocked encystation and excystation by over 85 %, and abrogated host-cell cytopathogenicity. Importantly, the same formulations exhibited potent bactericidal effects against methicillin-resistant Staphylococcus aureus and neuropathogenic Escherichia coli K1, while maintaining minimal cytotoxicity toward human cells. This dual-action approach signifies a step forward in the development of broad-spectrum anti-FLA therapeutics with potential for ocular and systemic applications.

Pathogenic Free-Living Amoebae and Human Health publication trend

The graph below shows the total number of articles in pathogenic free-living amoebae and human health across all publications each year (not limited to Nature Index journals).

Technical terms

Free-living amoebae: Protozoa inhabiting soil or water that can opportunistically infect humans.

Trophozoite: Active, feeding form of an amoeba responsible for tissue invasion.

Cyst: Dormant, resistant form that survives adverse conditions and facilitates transmission.

Encystation/Excystation: Processes of transformation into a cyst and reactivation into a trophozoite, respectively.

Antiamebic therapy: Pharmacological agents or regimens designed to eliminate amoebic infections.

References

1. The Orphan Drug for Acanthamoeba Keratitis (ODAK) Trial PHMB 0.08% (Polihexanide) and Placebo versus PHMB 0.02% and Propamidine 0.1%. Ophthalmology (2023).
2. Diagnosis, Clinical Course, and Treatment of Primary Amoebic Meningoencephalitis in the United States, 1937–2013. Journal of the Pediatric Infectious Diseases Society (2014).
3. Free-Living Amoebae as Hosts for and Vectors of Intracellular Microorganisms with Public Health Significance. Viruses (2017).
4. Antimicrobial activities of green synthesized gums-stabilized nanoparticles loaded with flavonoids. Scientific Reports (2019).
5. An update on Acanthamoeba keratitis: diagnosis, pathogenesis and treatment. Parasite (2015).