Morphology Acanthamoeba is characterised by a feeding and replicating trophozoite which, under adverse conditions, can form a dormant cyst stage. Biochemical characteristics Acanthamoeba is an aerobic organism and as such cannot exist as the trophozoite stage in environments with a low oxygen content. However, Acanthamoeba cysts have been isolated from anaerobic material such as faeces, sewage and other habitats low in oxygen. Acanthamoeba cysts are highly resistant forms capable of withstanding extremes of temperature, disinfection and desiccation. This accounts for the presence of the organism in virtually all soil, natural or man-made aquatic sites and even the atmosphere.
Trophozoites feed and replicate on the bacterial food source.
However, biochemical and molecular methods are necessary for the identification of the various Acanthamoeba species. Health effects Certain species of Acanthamoeba are pathogenic to humans causing two clinically distinct diseases, affecting the brain and the cornea respectively. Although Acanthamoeba is common in most environments, human contact with the organism rarely leads to infection. GAE is sub-acute or chronic and invariably fatal. The route of infection in GAE is unclear although invasion of the brain may be via the blood following a primary infection elsewhere in the body, possibly the skin or lungs.