Effects of Quaternary Ammonium Silane Coatings on Mixed Fungal and Bacterial Biofilms on Tracheoesophageal Shunt Prostheses

Abstract

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 ...

Current understanding of multi‐species biofilms

“…in biofilms formed at human chronic skin wounds [23]. FISH was also employed by Oosterhof et al to study mixed fungal and bacterial biofilms on tracheoesophageal shunt prostheses [24]. Not only in identification of microbial species, FISH based methods can also be used to estimate the physiological states of microbial cells.…”

ZnO films grown by pulsed-laser deposition on soda lime glass substrates for the ultraviolet inactivation of Staphylococcus epidermidis biofilms

“…When used alone SYTO 9 labels both live and dead bacteria green, in contrast propidium iodide penetrates those cells with compromised cell membranes. The staining method has been used extensively as a viability indicator [33][34][35][36][37][38][39][40]. The stain mixture ratio used in the majority of experiments was 75 : 25, SYTO 9: propidium iodide rather than the recommended 1 : 1 ratio, this was due to the red fluorescence being too prominent.…”

Candida biofilm formation on voice prostheses

“…Positively charged surfaces are strongly adhesive to the negatively charged bacteria; however, the positive charge inhibited biofilm progression from the initial adhesion stage toward the growth stage since immobilized QAS molecules interact with the cell membranes of adhering bacteria, presumably causing membrane leakage and cell death. Oosterhof et al (2006) demonstrated that QAS also reduces the number of viable bacteria and yeasts in mixed biofilms. 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 and bacteria compared with those for silicone rubber controls, as confirmed using confocal laser scanning microscopy after live/dead staining of the biofilms.…”