Seen above with H&E staining are ameba with hemorrhage and inflammation. The GMS stain below demonstrates the double wall characteristic for Acanthameba. The free-living ameba that can infect humans include Naegleria, Acanthameba, and Balamuthia. The latter two can cause granulomatous or hemorrhagic amebic encephalitis, usually in persons who are debilitated or malnourished, are undergoing immunosuppressive therapy for organ transplants, or have AIDS. CNS infection occurs through hematogenous spread from the respiratory tract or a skin ulceration. Acanthamoeba can become a disseminated infection. Naegleria is acquired by exposure to polluted water in ponds, swimming pools, and reservoirs. The portal of entry is the olfactory neuroepithelium. The pathologic changes are an acute hemorrhagic necrotizing meningoencephalitis.