Decreasing Cell Population of Individual Species Does Not Impair the Virulence of and Mixed Biofilms.

and are two commonly seen opportunistic fungi in clinical settings and usually co-isolated from the population inflicted with denture stomatitis and oropharyngeal candidiasis. Although and mixed biofilm is deemed to possess enhanced virulence compared with their individual counterparts (especially single biofilm), the relevant descriptions and experimental evidence on the relationship of virulence with their individual cell number in mixed biofilms are contradictory and insufficient. In this study, two standard isolate and eight ones were used to test the cell quantities in their 24- and 48-h single and mixed biofilms. A series of virulence factors including antifungal resistance to caspofungin, secreted aspartic proteinase (SAP) and phospholipase (PL) levels, efflux pump function and β-glucan exposure were evaluated. Through this study, the declines of individual cell counting were observed in the 24- and 48-h mixed biofilms compared with their single counterparts. However, the antifungal resistance to caspofungin, the SAP and phospholipase levels, the rhodamine 6G efflux and the efflux-related gene expressions were increased significantly or kept unchanged accompanying with reduced β-glucan exposure in the mixed biofilms by comparison with the single counterparts. These results reveal that there is a competitive interaction between and strains in their co-culture without at the expense of the mixed biofilm virulence. This study presents a deep insight into the interaction between and and provides new clues to combat against fungal infections caused by mixed biofilms.