Exogenous factors influencing voice prosthetic biofilm

The lifetime of a voice prosthesis is dependent on the amount and composition of the biofilm on the prosthesis (and also on the type of prosthesis). This biofilm formation is a multifactorial process which is difficult to study in an in vivo situation due to the multitude of influential factors. In a retrospective multifactorial analysis no factors could be found to have a significant effect on the lifetime of these devices. Therefore in this thesis, the effects of single factors on biofilm formation were studied using the artificial throat model. Biofilm growth in the artificial throats was initiated using the biofilm of an explanted Groningen voice prosthesis, without knowing the exact composition of this biofilm. This teleological approach was based on practical and technical considerations. As we used the same ‘explanted’ biofilm in all experiments including the controls, and performed the experiments in duplicate or triplicate, all experiments can be regarded as reliable and reproducible, within the limitations caused by working with viable microorganisms. In future in vitro studies using the artificial throat it is recommended to start flushing the artificial throat starting from day one, as comparable to the in vivo situation, and to imitate the physiological condition of the body temperature in the artificial throat by adjusting a heating device. The use of airflow, dairy products like buttermilk (containing the probiotic bacterium Lactococcus lactis), certain probiotic suspensions and the use of caffeinated soft drinks were found to diminish biofilm formation on voice prostheses under in vitro conditions. Although the exact ingredients responsible for the diminishing of biofilm formation including the viability of probiotic bacteria in commercially available health products were not determined in this thesis dairy products and probiotic suspensions have demonstrated a significant effect on biofim formation. Evaluation of the promising results of this study should be performed in a prospective, controlled cross-over in vivo study to further determine the relevance for the clinical practice.