Cells and Materials


Silicone rubber voice prostheses m patients after total laryngectomy become rapidly colonized by a biofilm, consisting of yeasts and bacteria. An especially troublesome feature of these biofilms is the ingrowth into the silicone rubber by colonizing yeasts. Microcolonies of ingrowing yeasts have been frequently observed on explanted voice prostheses after 3-4 months use. Incubation of silicone rubber samples in a modified Robbins device with a culture of Candida tropicalis, isolated from a Groningen button voice prosthesis, while passing the yeasts through a cycle of feasts (7 days) and famine (also 7 days) demonstrated, by electron microscopy, the onset of the ingrowth features as seen in vivo. In this paper, the in vitro capacities of four C. albicans and four C. tropicalis strains, all isolated from explanted voice prostheses, are compared. All eight strains showed onset of the ingrowth features observed in vivo: sometimes in the form of a small group of yeasts growing into a hole-like defect or, at other times in the form of clearly visible imprints in the silicone rubber, left after detachment of adhering yeasts during preparation of the samples for electron microscopy.