Biofilms on silicone rubber voice prostheses. Importance of lactobacilli and surface modification

PhD ceremony: Mr. K.J.D.A. Buijssen, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Biofilms on silicone rubber voice prostheses. Importance of lactobacilli and surface modification

Promotor(s): prof. B.F.A.M. van der Laan, prof. H.C. van der Mei, prof. H.J. Busscher

Faculty: Medical Sciences

Silicone rubber voice prostheses are used in patients after a total laryngectomy, because of laryngeal cancer. The functional lifetime is short due to biofilm formation. The microbial composition of voice prosthetic biofilms was explored using molecular techniques. Microorganisms were identified using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). For the first time it is described that lactobacilli are the predominant bacteria in biofilms, and grow intertwined with Candida. We were able to visualize the architecture better by using specific fluorescent labelled probes for Candida and lactobacilli, and clearly demonstrated their interaction.

The interaction between Candida en lactobacilli was studied in more detail in vitro. The C. albicans morphogenesis is regulated (inhibition of hyphae) and is important in biofilm formation. This can explain why lactobacilli could be beneficial to the in situ lifetime of silicone rubber voice prostheses. Because the prevention of biofilms is very important, we also evaluated voice prosthetic biofilm formation on antimicrobially-modified and smoothened silicone rubber voice prostheses. The inhibitory effects of positively charged coatings on the viability of yeast and bacteria in mixed biofilms are described. Using smoother surfaces may also prevent biofilm formation and we showed that the clinical lifetime was increased by a factor 2.1. It is recommended to use these findings on the available voice prostheses.