[An ultrastructural evaluation of Pneumocystis carinii].

The pneumocystis carinii (PNC) is a challenge, because its taxonomy has not been completely explained. PNC seems to be a chimera with fungal and parasitic characteristics. The objective of the present study is to analyze the different stages observed in PNC using transmission electron microscopy in order to correlate them with bibliographic reports regarding a possible taxonomic classification. The trophic stage was the form most frequently encountered in alveolar spaces and their organisms varying in size and shape from 6 to 20 microns. Cyst were round or oval, with diameters ranging between 4 and 12 microns, showing four intracystic bodies were individually limited by a membrane. Connections between the membrane of intracystic bodies and junctions between them and the inner cell membrane of the cyst wall were also observed. Our ultrastructural findings appear to be in agreement with several reports which considered PNC among the fungi, most likely related them to the non-gemating Ascomycetes.