Electron-microscopic observations of the Coccidioides immitis parasitic cycle in vivo.

BALB/c mice were inoculated by intranasal challenge with viable arthroconidia of C. immitis and in-vivo morphogenesis of the fungal pathogen was investigated by electron-microscopic examination of pulmonary lavage and cryofractured lung specimens. Samples were prepared at intervals over an 11-day period. Stages of spherule and endospore development were easily identified by scanning and thin-section electron microscopy. Details of morphogenesis of the pathogen in vivo closely resemble developmental aspects reported from in-vitro studies.