Two quaternary ammonium silanes (QAS) were used to coat silicone rubber tracheoesophageal shunt prostheses, yielding a positively charged surface. One QAS coating [(trimethoxysilyl)-propyldimethyloctadecylammonium chloride] was applied through chemical bonding, while the other coating, Biocidal ZF, was sprayed onto the silicone rubber surface. The sprayed coating lost its stability within an hour, while the chemically bonded coating appeared stable. Upon incubation in an artificial throat model, allowing simultaneous adhesion and growth of yeast and bacteria, all coated prostheses showed significant reductions in the numbers of viable yeast (to 12% to 16%) and bacteria (to 27% to 36%) compared with those for silicone rubber controls, as confirmed using confocal laser scanning microscopy after live/dead staining of the biofilms. In situ hybridization with fluorescently labeled oligonucleotide probes showed that yeasts expressed hyphae on the untreated and Biocidal ZF-coated prostheses but not on the QAS-coated prostheses. Whether this is a result of the positive QAS coating or is due to the reduced number of bacteria is currently unknown. In summary, this is the first report on the inhibitory effects of positively charged coatings on the viability of yeasts and bacteria in mixed biofilms. Although the study initially aimed at reducing voice prosthetic biofilms, its relevance extends to all biomedical and environmental surfaces where mixed biofilms develop and present a problem.Biofilm formation is the leading cause for the failure of biomedical prostheses (9, 13), including tracheoesophageal shunt prostheses, used for speech rehabilitation in patients after total laryngectomy because of a malignant laryngeal tumor. Tracheoesophageal shunt prostheses are made of a silicone rubber (SR) tube capped on one end with a one-way valve and are placed between the esophagus and the trachea. The valve of the prosthesis constitutes its esophageal side, and the one-way mechanism allows air to pass from the tracheal side, but fluids passing the esophagus are blocked from entering the trachea. Microorganisms readily form a biofilm on the esophageal side of a prosthesis, which leads to dysfunction of the valve and induces leakage of fluids in the trachea or increased airflow resistance during speech (3, 15). Consequently, the useful lifetime of a voice prosthesis ranges from 3 to 6 months (10, 15, 16).Tracheoesophageal shunt prosthetic biofilms contain a mixture of yeasts and bacteria, including Candida species, Staphylococcus and Streptococcus species, and Rothia dentocariosa. Especially Candida albicans, Candida tropicalis, and R. dentocariosa are known to reduce the lifetimes of tracheoesophageal shunt prostheses in vivo (5). Antimicrobials or antifungal agents, or both, have been administered to patients in order to eradicate these biofilms (18), but the biofilm offers effective protection against antimicrobials, to which planktonic organisms are usually susceptible (2, 7). Therefore, preventive measures seem a better way to ...

The results give a better understanding of biofilm formation and can be used in further development to prevent biofilm formation on voice prostheses.

Lactobacilli are general colonizers of tracheoesophageal voice prostheses in vivo, growing intertwined with Candida. This knowledge may be important in the development of new pathways directed to prevent or to influence biofilm formation on tracheoesophageal voice prostheses and elongate their lifespan.