Glutaraldehyde fixation is more advantageous for Malassezia furfur biofilm measurements.

The fixative most commonly used in biofilm measurement studies of pathogenic yeasts is ethanol. However, due to lipid dissolution in ethanol, this method may not be the optimal choice for certain yeasts which have a high lipid content in their cell walls, such as human pathogen Malassezia furfur. We conducted a study to compare the measurement values of 26 clinical strains of Malassezia furfur using glutaraldehyde and paraformaldehyde instead of ethanol. After the fixation step, standard staining methods were applied for biomass and extracellular polymers. Imaging was performed using scanning electron microscopy and optical coherence tomography. An important result for both biomass and extracellular polymers measurements, was that ethanol fixation group values were lower than other fixation methods (p < 0.001). The morphological formations, which were observed as small cohesive groups with ethanol fixation, were seen as adhesive groups with glutaraldehyde fixation. The application of glutaraldehyde in the fixation of biofilms produced by M. furfur yielded a greater range of absorbances, thus facilitating more comprehensive data evaluation than that achieved with ethanol. In yeasts such as Malassezia with a high lipid content in their cell wall, fixation with glutaraldehyde seems likely to contribute to easier analysis of comparative data in biofilm studies.