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Free living amoebae as causative agents of human infections are world wide occuring organisms with the ability of dual lifestyle both in nature, which is their original habitat, so within host tissue. The aim of this theses is to summarize the basic available knowledge of the pathogenic species Naegleria fowleri and Balamuthia mandrillaris and of the pathogenic genus Acanthamoeba which invade CNS and are causative agents of rare but serious human infections, often leading to death of a patient. The exception of their deathly consequences is an Acanthamoeba keratitis infection in which non curing cases lead to a significant visual impairment and even to visual loss. In each of the chapters, the work is tend to summarize transmision ability, mechanisms of pathogenesis and pathophysiology of these three free living amoebae in order to describe their ability to cause infection.

Naegleria fowleri, Balamuthia mandrillaris and Acanthamoeba spp. are free-living amoebae which rarely cause human infections. N. fowleri induces primary amoebic meningoencephalitis mostly among children and young adults. B. mandrillaris is the causative agent of Balamuthia amoebic encephalitis and skin lesions with complicated healing. Amoebas of the genus Acanthamoeba are the ethiologic agent of focal granulomatous encephalitis. Its clinical presentation is almost the same as in Balamuthia encephalitis, but it occures mainly in immunocompromised patients. It can also affect lungs and skin. The infection of central nervous system usually has a fatal end. In immunocompetent people Acanthamoeba keratitis can occur. Unproper use of contact lenses or trauma of the cornea represents increased risk level. Without correct treatment Acanthamoeba keratitis can lead to sight loss. In all infections caused by free-living amoebae, early diagnosis and initialisation of effective therapy are essential for better prognosis. This thesis discusses contemporary diagnostic and therapeutic approaches to these infections.