Morphological characteristics of Candida albicans, Candida krusei, Candida guilliermondii, and Candida glabrata biofilms, and response to farnesol

Background and Aim: Different Candida species isolated in humans and animals have different types of parasite activity. The most pathogenic species is Candida albicans followed by Candida tropicalis. However, the effects of the morphology of Candida krusei, Candida guilliermondii, and Candida glabrata biofilms on the pathogenicity of these species have not been fully characterized. To the best of our knowledge, there is no literature on the effect of farnesol on rare Candida species. This study aimed to check the effect of different farnesol concentrations on the species C. krusei, C. guilliermondii, and C. glabrata compared with the strain C. albicans ATCC 10231, which has been widely studied, and is a strong producer of biofilms. Materials and Methods: We studied the morphological and densitometric parameters of biofilms produced by Candida species under the influence of the drug farnesol (Sigma-Aldrich, St. Louis, MO). We used a heart brain broth with the addition of 2% bovine blood serum in 96-well plates. To each well, we added 100 μL of C. albicans, C. krusei, C. guilliermondii, or C. glabrata culture, and 0.2-400 μM farnesol. The microliter plates were cultured with the lid closed at 37°C for 48 h. Then, the liquid was removed, and the wells were washed 3 times with 200 μL phosphate buffer solution (pH 7.3). Biofilm fixation was performed using 150 μL of 96% ethanol for 15 min. Then, the microliter plates were dried for 20 min at 37°C, a 0.5% solution of crystalline violet was added, and the plates were placed in an incubator at 37°C. After 5 min, the contents of the wells were removed, washed 3 times with 200 μL of phosphate buffer solution (pH 7.2), and dried. The dye was extracted by washing with 200 μL of 96% ethanol for 30 min. The results were obtained using a photometric analyzer of enzyme immunoassay reactions at an optical density (OD) wavelength of 450 nm. Results: All of Candida spp. strains tested were susceptible to farnesol at concentrations ranging from 0.8 to 400 μM for C. albicans, C. krusei, and C. guilliermondii, and 12.5 to 400 μM for C. glabrata. Conclusion: This study provides new insights into the use of farnesol against biofilms produced by Candida species, but further studies in vivo are necessary to evaluate the effectiveness of the reduction of OD. To the best of our knowledge, the antimicrobial activity of farnesol against C. krusei, C. guilliermondii, and C. glabrata has not been reported previously, although studies have confirmed the inhibitory effect of farnesol on the growth of different microorganisms.