Adhesion to silicone rubber of yeasts and bacteria isolated from voice prostheses: influence of salivary conditioning films.

Abstract

Adhesion of yeasts and bacteria to silicone rubber is one of the first steps in the biodeterioration of silicone rubber voice prostheses. In this paper, adhesion of two streptococcal, staphylococcal, Candida albicans and Candida tropicalis strains, isolated from explanted voice prostheses was investigated to silicone rubber with and without a salivary conditioning film in a parallel-plate flow chamber. Within each microbial pair of one species, the strain with the most negative zeta potential adhered most slowly to negatively charged silicone rubber. No other clear relationships were obvious between adhesion to silicone rubber and microbial zeta potentials of cell-surface hydrophobicities, as by water contact angles. A 1.5-h adsorbed salivary conditioning film appeared to possess components, presumably albumin and lysozyme, slowing down the deposition of the yeasts and some of the streptococcal and staphylococcal isolates. In addition, microbial adhesion in a stationary end point was generally lower to silicone rubber with an adsorbed salivary conditioning film than without one. Nearly all microorganisms adhering to an adsorbed salivary conditioning film, yeasts as well as bacteria, were stimulated to detach by the passage of an air bubble through the chamber, but microorganisms adhering directly to the silicone rubber, especially C tropicalis strains, detached in far lower numbers under the influence of a passing air bubble. The present observations are in agreement with clinical in vivo findings that in patients with reduced saliva production after radiotherapy, the device life of the voice prosthesis is significantly shortened and suggests that isolated salivary components might be used as an anti-adhesive.