Adhesive interactions between voice prosthetic yeast and bacteria on silicone rubber in the absence and presence of saliva

Biofilms on silicone rubber voice prostheses are the major cause for freque nt failure and replacement of these devices. The presence of both bacterial strains and yeast has been suggested to be crucial for the development of voice prosthetic biofilms. Adhesive interactions between Candida albicans, Candida krusei, and Candida tropicalis with 14 bacterial strains, all isola ted from explanted voice prostheses were investigated in a parallel plate f low chamber. Bacteria were first allowed to adhere to silicone rubber, afte r which the flow chamber was perfused with yeast, suspended either in saliv a or buffer. Generally, when yeast were adhering from buffer and saliva, th e presence of adhering bacteria suppressed adhesion of yeast. In saliva, Ro thia dentocariosa and Staphylococcus aureus enhanced adhesion of yeast, esp ecially of C. albicans. This study shows that bacterial adhesion mostly red uces subsequent adhesion of yeast, while only a few bacterial strains stimu late adhesion of yeast, provided salivary adhesion mediators are present. I nterestingly, different clinical studies have identified R. dentocariosa an d S. aureus in biofilms on explanted prostheses of patients needing most fr equent replacement, while C. albicans is one of the yeast generally held re sponsible for silicone rubber deterioration.