Assessment of nanomechanical properties of Candida albicans as an element of the oral mycobiota in healthy subjects – a preliminary study

In a healthy physiological state, the mucous membrane of the oral cavity creates a suitable environment for the colonization of Candida spp. yeasts. The aim of the study was to analyze the nanomechanical properties of C. albicans cells derived from the oral cavity of healthy people in a biofilm produced in laboratory conditions. Candida spp. were sampled from the oral cavity of healthy individuals. The process of biofilm formation was analyzed using classic microscopic observation enriched with SEM (scanning electron microscope) and the nanomechanical properties of the cells were assessed with the use of the atomic force microscopy technique (AFM). From all isolated strains in the samples collected of the oral cavity healthy people was detected 79% C. albicans. Other isolated species belonged to the group „non-albicans”. The observations of C. albicans carried out in 24-h cultures revealed a tendency of the cells to form a biofilm structure with multilayer cell systems. The diameter of C. albicans cells in this structure was 5.75 µm, and the length of the pseudohyphae was 17.08 µm. The presence of an extracellular substance surrounding the C. albicans cells was detected. The mean value of the adhesion force determined for C. albicans cells was 4.01 nN. Areas with increased hardness (Force Modulation Mode signal; FMM signal) were found mainly in the zones of cells in contact with the glass substrate. The analysis of Candida cells in liquid samples gives satisfactory results, as it prevents unfavorable changes in the cell surface and thus provides more reliable results. The quality of the biofilm is probably related to the nanomechanical properties of C. albicans cells and may consequently contribute to the stability of the biofilm structures and their susceptibility or resistance to antifungal drugs.

The presence of Candida spp. especially in companion animals (dogs, cats) poses a risk of their transmission to the human organism. For this reason, it is advisable to undertake additional research to analyze the ability of zoonotic-origin Candida spp. to form biofilms with comparison of the biofilm-formation capacity of species isolated from humans.