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Microsporidia is a nontaxonomic
term referring to an extensive group of unicellular organisms classified
in the phylum Microspora. Previously considered to be primitive
protists, they have been reclassified as fungi.1 All
microsporidia lack mitochondria, are obligate intracellular parasites,
and possess a characteristic coiled extrusion apparatus consisting
of a polar tubule anchored to an anterior disk within the spore. This
apparatus is capable, upon extrusion, of penetrating the host cell
membrane and injecting the infectious sporoplasm material into the cytoplasm
where the life cycle begins (Fig. 302-1).
Of over 1200 species known, at least 14 species of microsporidia
have been described that are capable of infecting humans (Table 302-1).2 The pattern
of infection varies depending on the species of microsporidia and
the immune status of the host.
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Controversy existed as to ...