Aug98 COTM: Pneumocystis carinii in the Lung

August 1, 1998

Infectious Agents Case 1 Light Microsocopy Electron Microscopy Discussion Case 1 Case 2 Case 3 Case 4	Electron Microscopy of Infectious Agents Case 1: Pneumocystis carinii in the Lung Light Microscopy In the lung, Pneumocystis carinii appear histologically as foamy aggregates in the alveolar spaces. With the electron microscope, these foamy aggregates are composed of thick and thin-walled organisms, which represent the cystic and trophozoite forms of the organism. Electron Microscopy The organisms have characteristic filopodial extensions of the cell wall, and it is this feature that can be readily identified with the electron microscope.
	Figure 1. Magnify Image	This micrograph shows two collapsed thick-walled cystic forms (c) with extensions of the cell walls to form filopodia or pili (arrows), which characterize the organism. One of the cysts is budding and shows a partially formed wall, with communication between the two daughter organisms. Within the field are empty profiles of degenerated thin-walled trophozoites (t). Original mag = 17,300x.

	Figure 2. Magnify Image	The trophozoites may appear as single or multiple organisms within a cyst or as separate thin-walled forms

	Discussion

August 1998 Case-of-the-Month

Electron Microscopy of Infectious Agents