Determination of the effect of enzymes synthesized in Trichosporon asahii on biofilm formation and comparison of their antifungal susceptibility

Introduction and Aim: In recent years, Trichosporon asahii has emerged as the most common cause of invasive trichosporonosis, especially in immunocompromised patients. One of the most important virulence factors of Trichosporon asahii is biofilm formation, which creates resistance to antifungals and the environment. In this study, we aimed to elucidate the mechanism of biofilm formation in T. asahii, to determine the contribution of the glyceraldehyde-3-phosphate dehydrogenase enzyme, one of the enzymes synthesized during the biofilm formation process, to biofilm formation, and to determine whether there is a relationship between biofilm and antifungal susceptibility profiles. Material and Methods: Thirty patient isolates were included in the study. Crystal violet method was used to determine biofilm formation and firstly the method was optimized, then the biofilm levels of the isolates were grouped as low, medium and high biofilm forming. The amounts of GAPDH synthesized by the isolates were determined by Western-Blot method. Antifungal susceptibility profiles of the isolates against amphotericin B, fluconazole and posaconazole were determined according to CLSI-M27-A3 guideline for planktonic cells and by XTT reduction method for biofilm formation. The existence of correlation between biofilm formation, GAPDH production and antifungal susceptibility profiles was investigated by statistical analyses using Mann-Witney U, Kruskal Wallis, one-way ANOVA tests and Pearson Correlation analysis. Conclusions: In our study, it was observed that as the biofilm levels of the strains increased, the GAPDH levels increased and the difference between the GAPDH amounts of the low, medium and high level biofilm formations of the strains was statistically significant. In antifungal susceptibility tests, it was determined that the biofilm-forming cells had higher MIC values (MIC50, MIC90 and GM) than the planktonic cells. As far as we examined in the literature, we could not find any study examining the MIC results of posaconazole in biofilm formation in T. asahii and therefore our study is the first study in the world and in Turkey. It was seen that the logarithmic increase in POS MIC was 14≥log2≥10 in 73.33% of the strains. In addition, high POS MIC results showed that the use of POS in the treatment of biofilm-forming T. asahii infections was narrowed. It was determined that there was no significant correlation between the antifungal MIC log2 values between planktonic and biofilm-forming cells and biofilm levels and GAPDH amounts. This situation showed that the increase in MIC values in biofilm formation was not only due to the increase in GAPDH enzyme and there may be other factors. It was also seen that the sample type had no effect on biofilm formation. As far as we could examine, we believe that the optimized T. asahii biofilm formation method that we determined for the first time in our country during this study will also shed light on future studies.