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This paper discusses a study of three different amebae, including their biology, epidemiology and public health significance. Among the hundreds of small free-living amebae that exist in nature only threedifferent amebae belonging to the genera Acanthamoeba, Balamuthia and Naegleria,have been identified as agents of central nervous system (CNS) infections of humans andother animals. Several species of Acanthamoeba (e.g., A. castellanii, A. culbertsoni, A.hatchetti, A. healyi, A. polyphaga, A. rhysodes, and A. divionensis) and the only knownspecies of Balamuthia, B. mandrillaris, are known to cause a subacute and chronicdisease, granulomatous amebic encephalitis (GAE). Although more than 30 species ofNaegleria have been described, only one species, Naegleria fowleri, is known tocause an acute, fulminating disease, primary amebic meningoencephalitis (PAM).Acanthamoeba spp. also causes infection of the human cornea, Acanthamoeba keratitis. Additionally, both Acanthamoeba spp. and B. mandrillaris have been identified asagents of cutaneous infections in humans.Both N. fowleri and Acanthamoeba spp. are commonly found in soil, freshwater,sewage and sludge, and even dust in air. They feed on bacteria and multiply in theirenvironmental niche as free-living organisms. Several species of Acanthamoeba havealso been isolated from brackish water and seawater and from ear discharge, pulmonarysecretions, nasopharyngeal mucosa samples, maxillary sinus samples, mandibularautografts, and stool samples. Acanthamoeba spp. have also been known to hostbacterial pathogens such as Legionella spp., Mycobacterium avium, Listeriamonocytogenes, Burkholderia pseudomallei, Vibrio cholerae, and Escherichia coliserotype O157, which indicates the public health importance of these amebae.Balamuthia mandrillaris, the only species that has been described so far, has beenisolated from human and animal brains and only recently has it been isolated from soiland hence not much is available on the environmental niche of this ameba and its feedinghabits.The concept that these small free-living amebae could cause infections in humanswas developed by Culbertson and colleagues, who isolated Acanthamoeba sp., strain A-1(now designated Acanthamoeba culbertsoni) from tissue culture medium thought tocontain an unknown simian virus. They also demonstrated amebae in brain lesions ofmice and monkeys that died within a week after intracerebral inoculation with this strain.In 1965, Fowler and Carter identified for the first time a fatal infection due to free-livingamebae in the brain of an Australian patient which they thought was Acanthamoeba butnow it is now believed to have been due to Naegleria fowleri. Includes 14 references, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 9File Size: 1 file , 530 KB