[Microsporidia: general characteristics, infections and laboratory diagnosis]

Microsporidia are single celled, obligate intracellular, spore forming microorganisms which were first described as a cause of human disease in 1959. They are capable of infecting a wide variety of vertebrate and invertebrate hosts. Among the numerous microsporidial genera, seven have been described in human diseases such as Enterocytozoon, Encephalitozoon, Nosema, Pleistophora, Trachipleistophora, Vittaforma, Brachiola. Among these, Enterocytozoon bieneusi is the most frequently identified microsporidian in the patients. Features used in identification include spore size, nuclear configuration of spores, the number of polar tubule coils and the parazite-host interaction. In the development of Microsporidia, there are two different phases, called as proliferative phase and sporogonic phase. The only stage of Microsporidia outside the host is infective spores. The microsporidial spore is highly specialized, environmentally resistant structure that varies in size and shape according to species. They can cause infections both in immunocompetent subjects and immunocompromised patients such as AIDS. Although it can cause self-limiting infections in immunocompetent patients, it can cause severe life threating infections especially AIDS patients. In this review, the basic biology, epidemiologic characteristics and immunopathogenesis of Microsporidia, together with the diagnosis and treatment of the infections have been discussed.