Adhesion of oral Candida species to human buccal epithelial cells following brief exposure to nystatin

Opportunistic oral infections caused by Candida albicans and non-albicans Candida species are particularly common in compromised patients. Nystatin, which belongs to the polyene group of antimycotics, is frequently used as a topical agent in the treatment of oro-pharyngeal candidosis. It is recognized that due to the delivery mode of nystatin (i.e. topical, intermittent), as well as the cleansing effect of saliva within the oral environment, the yeasts undergo a relatively brief exposure to this drug during treatment. Nevertheless, there is a sparsity of data on the effect of such brief exposure to nystatin on the pathogenic attributes of Candida such as their adherence to host surfaces. The adhesion of microbes to host mucosal surfaces is a major determinant of successful colonization and Infection. Thus the main aim of our investigation was to compare the in vitro adhesion of 30 oral isolates of Candida belonging to six different species (comprising Candida albicans, Candida tropicalis, Candida glabrata, Candida guilliermondii, Candida krusei and Candida parapsilosis) to human buccal epithelial cells, following their brief exposure (1 h) to minimum inhibitory concentration of nystatin, and subsequent removal of the drug. The adhesion of these isolates to buccal epithelial cells was assessed by a previously described adhesion assay. Compared with the controls, there was a significant reduction in buccal epithelial cell adhesion of all six Candida species after drug exposure (54%-68%). However the adhesion of C. albicans isolates was the least affected by nystatin exposure, which was significantly different from that of the non-albicans species. These findings imply that sub-therapeutic levels of nystatin, which are likely to persist in the oral cavity during dosing intervals, may also be beneficial, as they inhibit candidal colonization. The significant difference in nystatin-induced suppression of adhesion between C. albicans and the non-albicans species investigated is a further testimonial for the pre-eminent virulence of the former species.