Opportunistic Free-Living Amebae, Part II

Abstract 

The free-living amebae Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri have been recognized as etiologic agents of amebic encephalitis. Although each has its own morphologic, ecologic, and epidemiologic traits, they have in common the ability to tolerate mammalian body temperature and cause infections. The amebic diseases are difficult to diagnose clinically, leading to delay in treatment, resulting in a high mortality rate. The major tests for the diagnosis of these diseases include immunostaining for amebae in brain and other tissues and conventional and real-time PCR. Balamuthia causes a subacute, though deadly, infection in either healthy or immunocompromised hosts, while Naegleria fowleri produces a fulminant infection invariably associated with exposure to freshwater. In Part II of this article, cultivation, the diseases, pathophysiology of infections, mechanisms of pathogenesis, therapy and prognosis, and, finally, prevention and control are reviewed for both of these free-living amebae. Little is known about Sappinia because there is but a single case on record.