Purpose: To develop a new screening method for rapid assessment of growth and biofilm formation by Aspergillus carbonarius, a well-known mycotoxigenic fungus, in microtiter plates, in relation to the initial spore inoculum and medium composition.
Methods: 96-well microtiter plates with synthetic grape juice medium (SGM) or yeast extract sucrose (YES) broth and 3 spore concentrations of A. carbonarius (103, 104,and 105spores/ml) were incubated for 7 days at 25°C. Fungal growth/biofilm formation was assessed by optical density (OD) at 575 nm after staining the wells with 0.5% crystal violet.
Results: Both fungal growth rate and lag phase duration depended on initial spore concentration, while biofilm formation was correlated negatively with lag phase and positively with OD at the 5th day of incubation. Biofilm formation was dependent on initial spore concentration for both substrates (p<0.05). When SGM was used, 104 and 105 spores resulted in comparatively higher and significantly different biofilm formation compared to control samples (non inoculated broth). On the contrary, for YES broth only 103 spores led to higher biofilm formation over controls. Statistically higher biofilm formation was observed on SGM in comparison to YES broth for specific inocula (103 and 105 spores).
Significance: Τhe proposed technique could serve as a rapid detection system for both fungal growth and biofilm formation by filamentous fungi.