Acanthamoebiasis

Acanthamoeba spp. have been found in the throat; mouth pipetting of fluids into cell culture has given rise to contaminated cell cultures in numerous instances. In the throat the amoebae appear to be nonpathogenic. However, in patients with long-standing immunosuppression, tissue invasion does occur, usually leading to encephalitis which is fatal and occasionally to focal lesions elsewhere. The inflammation is mononuclear, partially in response to necrosis of brain tissue, and is sometimes stated to be granulomatous; hemorrhage may be marked. Large amoebic trophozoites and smaller cysts with an irregular “corrugated” wall are found in the lesions. Often the amoebae (Figs. 1 and 2) are difficult to distinguish from macrophages; the latter have intensely staining nuclei, whereas the amoebae have vesicular nuclei and a “foamy” cytoplasm. The inflammatory reaction is of course variable because of immunosuppression of the patients (Pathology). The amoebae are not found in the spinal fluid....