A simple silicone elastomer colonization model highlights complexities of Candida albicans and Staphylococcus aureus interactions in biofilm formation

Introduction. Healthcare-associated infections (HAIs) significantly contribute to the burden of antimicrobial resistance. A major factor in HAIs is the colonization of indwelling medical devices by biofilm-forming opportunistic pathogens such as Candida albicans and Staphylococcus aureus. These organisms frequently co-infect, resulting in synergistic interactions with enhanced virulence and resistance to treatment. Hypothesis/Gap statement. C. albicans and S. aureus readily form dual-species biofilms on silicone elastomers, a commonly used medical device material, yet the colonization phenotypes of these organisms on such surfaces remain poorly understood. Aim. We aimed to develop a simple, optically tractable model to mimic the colonization of indwelling medical devices to investigate C. albicans and S. aureus biofilm formation. Methodology. The system utilizes discs of a silicone elastomer embedded in agar, reflecting device-associated conditions and enabling high-resolution imaging of biofilms formed by C. albicans and S. aureus co-cultures. Results. Initial results using the silicone elastomer colonization model reveal robust biofilm formation. These biofilms exhibited morphological differences between dual-species biofilms formed by S. aureus co-cultures with either yeast- or hyphal-form C. albicans, indicating the impact of differing C. albicans cell morphotypes in biofilm-associated medical device colonization on silicone elastomers. Quantification of biofilm formation by crystal violet staining provided further validation of the system. Conclusion. These findings underscore the importance of developing tools for biofilm study which more closely resemble the infectious microenvironment, with our work detailing such a system which can be employed in further study to improve strategies against device-related HAIs.