For successful colonization and infection by various microorganisms depend upon and ability to adhere to host mucosal surfaces. Although adhesion of bacteria to cell surfaces has been extensively investigated, but there are few studies dealing with the adhesion of fungi to epithelial cells, and most studies involved the opportunistic fungus Candida albicans. Lil jemark and Gibbons (1973) used an optical method to count Candida albicans attached to rat tongue and cheek cells. The kinetics of Candida albicans attached to rat tongue and cheek cells. The kinetics of Candida albicans adherence to. buccal epithelial cells have been investigated by Kimura and Pearsall (1978), who reported enhanced adherence to the organisms under conditions promoting yeast: germination. In´ addition, King et al .(1980) reported that Candida albicans adherence to the human vaginal epithelial cells and appears to adhere better than other ´ species of Candida.
Studies of Candida albicans attachement of oral epithelial cells suggest that attachement is mediated by epithelial cell receptors containing mannose moieties similar to those involved in bacterial attachment (Sandin et al, 1982; Centeno et al, 1983). A thorough understanding of factors mediating yeast attachment, however, has not been attained.
It studied the in vitro adherence of normal and UV-irradiated Candida albicans to human buccal epithelial cells and evaluated multiple factors influencing fungal adherence to human mucosal cells. And also studied ultrastructural changes of Candida albicans during adherence to buccal epithelial cells.
The results as follows.
1. The germ-tube forming activity of normal Candida albicans treated with rabbit serum at 37°C for 3 hours incubation was 91.5% but the activity of UV-irradiated Candida albicans was 29.0%.
2. The lethal dose 50 (LD50) of normal strains in mice was 5.0 x 10" cells/ml, but LD50 could not be observed in the UV- irradiated strains even with 1.0 x 105 cells/ml. It demonstrated that the virulence is decreased in the UV-irradiated strains.
3. The adherence of normal Candida albicans to human buccal epithelial cells (188.8 ± 19.6 cells/100 BECs) was significantly greater than UV- irradiated Can-dicta albicans (117.2 ± 16.6 cells/100 BECs)
4. On comparison of adherence of viable and nonviable (heat killed) Candida albicans to human buccal epithelial cells, the nonviable strains demonstrated poorer adherence than the viable strains.
5. Candida albicans cultured at 37°C adhered to human buccal epithelial cells in greater number than the culture at 25°C.
6. The adherence of normal Candida albicans was directly proportional to the in-cubation time.
7. The adherence ability was maximum at pH 7.0.
8. The adherence of Candida´ albicans depended upon yeast cell concentrations and when the yeast concentrations was above 106 cells/ml, the activity of adherence was significantly increased.
9. The adherence in medium containing of carbohydrates of normal Candida albicans, sucrose and galactose showed only slight increase but, conversely,, mannose show-ed slightly decreased yeast attachment.
10. Candida albicans adheres to buccal epithelial cells to a significantly greater degree than the other, species .tested. Candida tropicalis and Candida stellatoidea-demonstrated moderate adherence capabilities, while Candida parapsilosis adhered only to a slight degree
11. Scanning electron micrography demonstrated Candida albicans adherent to and penetrating the buccal epithelial cells, and extracellular materials covered organism cell surfaces. In transmission electron micrography Candida albicans showed five distinct layers in the cell wall and floccular materials adherent to the outer surface: There was no evidence of damage to the host cell surface ex-cept at the site of entry.
A strong correlation was shown between germ-tube forming activity and increas-ed adherence of Candida albicans to human buccal epithelial cells, indicating that these activities were responsible for Candidal virulence.
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