Establishment of epidemiological cutoff values for Fonsecaea pedrosoi, the primary etiologic agent of chromoblastomycosis, and eight antifungal medications

Summary

Chromoblastomycosis is a serious fungal skin infection caused by a fungus called Fonsecaea pedrosoi, particularly affecting people in tropical regions and those in poverty. Researchers from multiple countries tested 148 samples of this fungus against eight different antifungal medications to determine how well each drug works. They established baseline measurements that doctors can use to determine if a patient’s fungal infection might not respond well to standard treatments, helping guide better treatment decisions.

Background

Chromoblastomycosis is a neglected tropical disease caused by dematiaceous fungi, with Fonsecaea pedrosoi being the most commonly reported etiologic agent globally. Limited antifungal susceptibility data exist for F. pedrosoi, making interpretation of minimum inhibitory concentration results difficult. Epidemiological cutoff values are needed to monitor antifungal resistance trends and guide treatment selection.

Objective

To perform antifungal susceptibility testing on F. pedrosoi isolates and establish minimum inhibitory concentration distributions and epidemiological cutoff values for eight antifungal medications commonly used to treat chromoblastomycosis.

Results

Calculated epidemiological cutoff values were: itraconazole 0.5 µg/mL, voriconazole 0.5 µg/mL, posaconazole 0.5 µg/mL, isavuconazole 1 µg/mL, terbinafine 0.25 µg/mL, and amphotericin B 8 µg/mL. Ketoconazole showed bimodal distribution with no ECV determined, and flucytosine was rejected due to marked variability. Percentages of non-wild-type isolates were low across most antifungals.

Conclusion

These epidemiological cutoff values provide a baseline for understanding the in vitro antifungal susceptibility profile of F. pedrosoi and monitoring resistance trends. The values can help clinicians detect non-wild-type isolates, reevaluate therapeutic options, and investigate potential clinical resistance. Further work on standardized protocols and reference strains is recommended.
Scroll to Top