Aspects related to biofilm production and antifungal susceptibility of clinically relevant yeasts of the genus Trichosporon

Lay Summary This study investigated 59 isolates of the medically important yeast Trichosporon in relation to their ability to form biofilms and the susceptibility of biofilms to antifungal agents. All isolates were able to produce biofilms and biofilms showed lower antifungal susceptibility. Trichosporonosis corresponds to a systemic fungal disease that leads to high mortality rates and is frequently associated with medical devices. It affects immunosuppressed patients in particular and is strongly linked to acquired human immunodeficiency, organ and tissue transplants, and malignant hematologic diseases such as leukemia and lymphomas. Trichosporon infections have been increasingly reported worldwide; however, little information is available either about their characteristics or the causative microorganism. Thus, the aims of the present study were: to investigate 59 yeasts of the genus Trichosporon by verifying the biofilm formation capacity of isolates; to analyze the susceptibility patterns of planktonic cells against the antifungals fluconazole, itraconazole, amphotericin-B, voriconazole, and caspofungin by comparing European Committee for Antimicrobial Susceptibility Testing (EUCAST) broth microdilution technique with the commercial method Etest; and to assess the susceptibility patterns of biofilm cells (sessile) against the same antifungals through broth microdilution. The ability to form biofilm on the surface of polystyrene plates was noted for all isolates, and 54.3% of samples were considered strong producers. Comparison between the antifungal susceptibility techniques evidenced that Etest showed higher and discordant minimum inhibitory concentrations (MICs) from those obtained by the microdilution method, especially for fluconazole, itraconazole, and caspofungin. Considering the susceptibility of biofilms, most species had high MIC50 and MIC90 against the tested antifungals, showing 4-to-66-fold higher concentrations for amphotericin B and 2-to-33-fold greater concentrations for caspofungin. These results highlight the importance of further studies with Trichosporon spp. for comparison between laboratory findings and in vivo response, considering both the susceptibility tests and the behavior of biofilm cells against drugs.

Automated summary

This study investigated the biofilm formation ability of 59 isolates of the medically important yeast Trichosporon and their susceptibility to antifungal agents. All isolates were able to form biofilms and showed lower susceptibility to antifungal drugs. Trichosporonosis is a systemic fungal disease with high mortality rates, commonly associated with medical devices and immunosuppressed patients. The susceptibility of biofilm cells to antifungals was higher than that of planktonic cells, and different methods for testing susceptibility showed discrepancies in minimum inhibitory concentrations, especially for fluconazole, itraconazole, and caspofungin. These findings highlight the need for further studies on Trichosporon spp. to better understand their characteristics and response to treatment.