Interactions betweenCandida albicansandStaphylococcus aureuswithin mixed species biofilms

Staphylococcus aureus and Candida albicans form dense biofilms together on internal medical devices and in doing so, establish a source of infection that is difficult to treat and can cause extensive local and systemic disease. The goal of the present study was to gain further insight into whether interactions between these two species within a biofilm alter their attachment to artificial surfaces and growth rates. After first establishing that S. aureus and C. albicans interact with one another and grow well together in the described biofilm system, the two species were mixed and attachment was assessed. S. aureus had differing effects on yeast attachment depending on when the two were mixed whereas C. albicans had no noticeable affect on S. aureus attachment. Examination of mixed biofilm structural integrity revealed that pure C. albicans biofilms have higher levels of detachment after 16 h of growth and a lower resistance to shear stress than do mixed biofilms. Similarly, measurement of biofilm growth rates indicated that chemical and metabolic interactions between the two species result in changes to their growth rates within biofilms. Collectively, the findings presented here suggest that S. aureus and C. albicans have a complex relationship that involves a variety of physical and chemical interactions. As a result, we believe new treatment strategies should focus on disrupting the community as a whole and all of its interactions rather than targeting individual members of the biofilm.