Ultrastructural features of host-parasite relationship in oral candidiasis.

In oral candidiasis, many keratinized epithelial cells and cells of Candida albicans are shed. Scales from patients with oral candidiasis were used for electron microscopic study of the epithelial-fungal relationship. Scales, scraped from the tongue and oral mucosa, were fixed for fungi. Electron microscopic observations showed cells of C. albicans outside, penetrating, or within the epithelial cells. Extracellular fungi possessed a floccular material adherent to the outer surface of the cell wall. Intracellular fungi lacked the floccular material which appeared to detach as fungi invaded the epithelial cells. Large vacuoles, which sometimes contained myelin figures, occupied the cytoplasm of fungal cells. Epithelial cells frequently contained several fungi. Discontinuous plasma membranes marked sites of fungal entry. Cytoplasmic areas devoid of fungi showed many tonofibrils, but the cytoplasm adjacent to fungi often lacked tonofibrils. Micrographs suggested that fungal cells lysed the tonofibrils. Bacteria were abundant in the scrapings, but always occupied an extracellular position.