Conditioning film and environmental effects on the adherence of Candida spp. to silicone and poly(vinylchloride) biomaterials

The reported incidence of colonization of oropharyngeal medical devices wit h Candida spp. has increased in recent years, although few studies that hav e systematically examined the adherence of yeast cells to such biomaterials , the primary step in the process of colonization. This study, therefore, e xamined the effects of oropharyngeal atmospheric conditions (5% v/v carbon dioxide) and the presence of a salivary conditioning film on both the surfa ce properties and adherence of Candida albicans, Candida krusei and Candida tropicalis to PVC and silicone. Furthermore, the effects of the salivary c onditioning film on the surface properties of these biomaterials are report ed. Growth of the three Candida spp. in an atmosphere containing 5% v/v CO2 significantly increased their cell surface hydrophobicity and reduced the zeta potential of C. albicans and C. krusei yet increased the zeta potentia l of C. tropicalis (p <0.05). Furthermore, growth in 5% v/v CO2 decreased t he adherence of C. tropicalis and C. albicans to both PVC and silicone, how ever, increased adherence of C. krusei (p <0.05). Pre-treatment of the micr oorganisms with pooled human saliva significantly decreased their cell surf ace hydrophobicity and increased their adherence to either biomaterial in c omparison to yeast cells that had been pre-treated with PBS (p <0.05). Sali va treatment of the microorganisms had no consistent effect on microbial ze ta potential. Interestingly, adherence of the three, saliva-treated Candida spp. to saliva-treated silicone and PVC was significantly lower than whene ver the microorganisms and biomaterials had been treated with PBS (p <0.05) . Treatment of silicone and PVC with saliva significantly altered the surfa ce properties, notably reducing both the advancing and receding contact ang les and, additionally, the microrugosity. These effects may contribute to t he decreased adherence of saliva-treated microorganisms to these biomateria ls. In conclusion, this study has demonstrated the effects of physiological conditions within the oral cavity on the adherence of selected Candida spp . to biomaterials employed as oropharyngeal medical devices. In particular, this study has ominously shown that these materials act as substrates for yeast colonization, highlighting the need for advancements in biomaterial d esign. Furthermore, it is important that physiological conditions should be employed whenever biocompatibility of oropharyngeal biomaterials is under investigation. (C) 2001 Kluwer Academic Publishers.