MICROBIOLOGY

• Eight species described: A. castellanii, A. polyphaga, A. culbertsoni, A. hatchetti, A. rhysodes, A. lugdunensis, A. quina, A griffini.[12]
• Ubiquitous in nature: isolated from air, soil, fresh water, salt water, chlorinated swimming pools, sewage, heating and ventilation systems.
• Two-stage life cycle
  • Actively feeding and dividing trophozoites that are pleomorphic, without flagella, and 14-40 μm in diameter.
  • Dormant cysts are double-walled, 10-25 μm in diameter, and resistant to chlorine, low temperature, antibiotics, pH extremes.
    • Three groups (I, II, III) of Acanthamoeba spp. based on cyst morphology.[13]
    • Encystation occurs under environmental stress: food deprivation, desiccation, change in temperature.
• Transmission: inhalation most common route with hematogenous spread; direct inoculation of skin.
• Described as “Trojan horses” as they can harbor intracellular bacteria, referred to as endosymbionts, which benefit by increased survival or enhanced pathogenicity from interacting with Acanthamoeba.[7][3]