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

<b>Introduction.</b> 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 <i>Candida albicans</i> and <i>Staphylococcus aureus</i>. These organisms frequently co-infect, resulting in synergistic interactions with enhanced virulence and resistance to treatment.<b>Hypothesis/Gap statement.</b> <i>C. albicans</i> and <i>S. aureus</i> 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.<b>Aim.</b> We aimed to develop a simple, optically tractable model to mimic the colonization of indwelling medical devices to investigate <i>C. albicans</i> and <i>S. aureus</i> biofilm formation.<b>Methodology.</b> The system utilizes discs of a silicone elastomer embedded in agar, reflecting device-associated conditions and enabling high-resolution imaging of biofilms formed by <i>C. albicans</i> and <i>S. aureus</i> co-cultures.<b>Results.</b> Initial results using the silicone elastomer colonization model reveal robust biofilm formation. These biofilms exhibited morphological differences between dual-species biofilms formed by <i>S. aureus</i> co-cultures with either yeast- or hyphal-form <i>C. albicans,</i> indicating the impact of differing <i>C. albicans</i> 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.<b>Conclusion.</b> 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.