Cell surface hydrophobicity-associated adherence of Candida dubliniensis to human buccal epithelial cells

Microbial adherence to mucosal surfaces is an important first step in the initiation of the pathogenic process in the oral cavity. Candida albicans, the most adherent and pathogenic Candida species, utilizes a variety of mechanisms to adhere to human tissues. Although the strongest mechanism of adherence involves mannoprotein adhesins on C. albicans, cell surface hydrophobicity (CSH) plays an important role in the adherence process by providing hydrophobic interactions that turn the initial attachment between the yeast and a surface into a strong bond. Recent cell wall analytical and comparative studies showed that, Candida dubliniensis, unlike C. albicans, possesses cell surface variations that allow it to be constantly hydrophobic, regardless of growth temperature. Based on these observations, the present study was designed to compare the adherence abilities of C. dubliniensis and C. albicans to pooled human buccal epithelial cells (BEC), in regards to their cell surface hydrophobicity. Ten C. albicans and nine C. dubliniensis isolates, as well as the C. albicans hydrophobic variant A9V10 were evaluated for adherence with BEC using visual aggregation in the wells of a microtiter plate and microscopic examination. All 11 C. albicans isolates failed to show adherence to BEC, visually or microscopically, when grown at 37 degrees C. The same isolates, however, showed significant increase in aggregation and microscopic adherence to BEC when grown at 25 degrees C. All C. dubliniensis isolates tested and the A9V10 C. albicans hydrophobic variant resulted in visual aggregation and adhered to BEC when grown at either temperature. The findings from this study show that, based on comparative adherence results and growth temperature changes, C. dubliniensis seems to have greater adherence to BEC than do typical C. albicans strains and that hydrophobic interactions seem to be the mechanism of adherence involved. Although many questions remain to be answered regarding the clinical implications of this observed in vitro enhanced adherence of C. dubliniensis to human BEC, these findings support the establishment of this novel species as a clinically significant yeast.