Effects of tea extracts on the colonization behaviour of Candida species: attachment inhibition and biofilm enhancement

PURPOSE: We assessed the effects of four different types of tea extracts (green, oolong, black and pu-erh tea) on cellular surface properties (hydrophobicity and auto-aggregation) and the colonization attributes (attachment and biofilm formation) of four strains of Candida albicans and three strains of Candida krusei.

METHODOLOGY: The cellular surface properties were determined using spectrophotometry. The colonization activities were quantified using colorimetric viability assays and visualized using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS: The tea extracts, in general, reduced the hydrophobicity (by 8-66 %) and auto-aggregation (by 20-65 %), and inhibited the attachment of two C. krusei strains (by 41-88 %). Tea extracts enhanced the biofilm formation of one C. albicans and two C. krusei strains (by 1.4-7.5-fold). The observed reduction in hydrophobicity strongly correlated with the reduction in attachment of the two C. krusei strains (P<0.05). The ultrastructural images of the tea-treated C. krusei biofilm cells demonstrated central indentations, although they remained viable.

CONCLUSION: The tea extracts have the ability to retard C. krusei adhesion to glass surfaces, possibly by reducing fungal cellular hydrophobicity, whilst paradoxically promoting biofilm formation. In practical terms, therefore, consumption of tea beverages appears to have a complex effect on oral candidal colonization.