Acanthamoeba spp. is a topic covered in the Johns Hopkins HIV Guide.

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  • Free-living ameba: Acanthamoeba spp, Naegleria fowleri, Balamuthia mandrillaris, Sappinia pedata.[4]
  • 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 & dividing trophozoites (14-40 μm in diameter)
    • Dormant cysts (double-walled 10-25 μm in diameter); cysts resistant to chlorine, low temperature, antibiotics, pH extremes.
      • Three groups (I, II, III) of Acanthamoeba spp described, division based on cyst morphology.[11]
      • Encystation occurs under environmental stress: food deprivation, desiccation, change in temperature.
  • Transmission: inhalation most common route; direct inoculation of skin
  • Described as “Trojan horses” as they can harbor intracellular bacteria.[4]

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Last updated: October 22, 2013