Clinical isolates and laboratory reference C andida species and strains have varying abilities to form biofilms

C andida biofilms are a major virulence trait for this yeast. In this study, the biofilm‐forming ability of the major medically important clinical and laboratory reference strains was compared. Biofilms were quantified using traditional methods, that is, crystal violet ( CV ), tetrazolium ( XTT ) reduction and colony‐forming unit assays ( CFU ), and two new methods: an automated cell counter ( ACC ) and biofilm suspension turbidity ( BST ) method. Biofilms could be categorized based on biofilm biomass (high, medium and low) and growth state (high and low). C andida albicans genotypes, A , B and C , showed medium biofilm mass and low growth rate, and only one C . albicans laboratory strain, ATCC MYA ‐2719, matched this biofilm category. Of all non‐ albicans C andida species tested, only C andida dubliniensis and C andida glabrata laboratory and clinical isolates had similar biofilm development. The ACC and BST methods for measuring biofilm significantly correlated with CV and CFU biofilm mass measurements. Thus, biofilm mass can be rapidly assessed using biofilm disruptive/cellular nondestructive methods allowing yeast biofilm cells to be used for further analysis. In conclusion, C andida laboratory reference strains and clinical isolates have been shown to form biofilms at different rates; hence for validity, the selection of laboratory reference strains in biofilm studies may be critical for virulence assessment.