Biofilm susceptibility testing on a three dimensional oral mucosal culture. Candida biofilms were grown for 24 h and subsequently exposed to antifungal drugs (4 μg/ml amphotericin B, 70 μg/ml fluconazole or 8 μg/ml caspofungin) or neutrophil-like HL-60 cells at an effector to target cell ratio of 10:1, for 24 additional hours. (A) The effects of antifungal agents on biofilms were quantitatively assessed by the XTT and qRT-PCR assays. Results represent the mean ± SD of one representative experiment where each condition was set up in triplicate. *p < 0.01 for comparison between XTT and qRT-PCR in each condition. (B) PAS stain of histologic sections showing the ability of the biofilm organisms to invade into the submucosal compartment after exposure to antifungal drugs or leukocytes. Black arrows: submucosal compartment. White arrows: epithelial layer. Microorganisms appear in dark blue.