Effect of subsequent passages on biofilm formation intensity, ALS genes expression, and cell surface hydrophobicity variability in clinical Candida albicans isolates

Candida albicans is an opportunistic yeast pathogen that have several virulence factors included biofilm formation, cell surface hydrophobicity (CSH), and the expression of adhesion genes. Concerns exist that serial laboratory subculturing may diminish these traits, leading to inaccurate research findings. Aim of this study was evaluated the effect of subsequently subcultures on biofilm formation intensity, ALS gene expression, and surface hydrophobicity properties in clinical C. albicans isolates. Ten clinical C. albicans isolates were serially subcultured up to 20 passages (P). We used qPCR to quantify ALS1 and ALS3 gene expression, the Crystal Violet assay to measure biofilm formation intensity (P1, P5, P10, P15, P20), and a water-octane partitioning assay for CSH variability at different passages. Serial subculturing caused gradual downregulation of gene expression for both ALS1 and ALS3 (p < 0.001). This condition was accompanied by a biofilm-forming capacity that became progressively reduced in 90% of isolates, whereas 60% at P20 were already biofilm-negative (vs. 10% at P1). Cell surface hydrophobicity also decreased progressively, with 100% of isolates displaying low CSH at P15, compared with 40% in the initial P1 state. Serial subculturing leads to a rapid reduction of C. albicans pathogenic fitness with decreased expression of certain key adhesion genes, diminished biofilm formation, and lower CSH. These results highlight the plasticity of the organism and thus strongly suggest that low-passage clinical isolates should be used in studies to reflect true pathogenicity in vivo accurately.