The Effect of pH on Adhesion and Hyphal Formation by Strains of Candida albicans

Abstract

The adhesion of five strains of Candida albicans to smooth acrylic was compared. Early exponential phase cells were suspended in buffers at pH 2.6–7.3 and allowed to adhere to acrylic pieces. Attachment was measured in terms of percentage area coverage of a microscopic field covered by cells, using automated image analysis. The strain that adhered in the highest numbers also adhered best at pH 7.3; however, for the other strains pH did not significantly influence adhesion. Two strains, isolated from cases of denture stomatitis, produced hyphae, particularly at lower pH values, in buffer without any carbon or nitrogen sources. For two ‘carrier’ strains hyphal formation was minimal. The fifth strain studied did not produce hyphae although it had been isolated from a case of denture stomatitis. A strain from each of the above categories was selected and the adhesion to buccal epithelial cells (BEC) was measured, at pH 7.3,6.0 and 2.6, using a visual microscopic count. All strains were capable of adhering at all the pH values studied although the adhesion was low (1–9 Candida cells per BEC). The adhesion of the strains to BEC was increased when stationary phase cells were used compared to early exponential phase cells. Strain GDH 2346 produced hyphae at pH 2.6. All strains gave a very low cell surface hydrophobicity which could not be related to the ability of strains to adhere to either acrylic or BEC.

Key Words:

• pH
• Adhesion
• Candida albicans
• Buccal epithelial cells
• Acrylic
• Denture stomatitis