Understanding chromoblastomycosis in Sri Lanka; insights into fungal aetiology and antifungal susceptibility patterns

Introduction: Chromoblastomycosis is a chronic disfiguring fungal infection of the subcutaneous tissue found mainly in the socio-economically marginalized population in the tropical and sub-tropical regions, characterized by the presence of sclerotic cells. This study was done with the aim of identifying the antifungal sensitivity patterns of the causative agents of chromoblastomycosis in Sri Lanka from 1992 to 2019.Methodology: Study was done on the stored isolates received from patients with chromoblastomycosis since 1992 to 2019, to the Mycology Reference Laboratory of Medical Research Institute, Colombo. Isolates were revived by subculture on Potato dextrose agar. Identification was done phenotypically. Antifungal sensitivity testing was performed by E test method. Available demographic and clinical data were analysed.Results: Of the 74 isolates, 71 (96%) were caused by Fonsecaea pedrosoi. Mean MIC for the antifungals tested were lowest for posaconazole 0.015 μg/ml followed by itraconazole 0.225 μg/ml, and voriconazole 0.768 μg/ml while amphotericin B demonstrated complete resistance with mean MIC of 30.591 μg/ml. No statistically significant differences were noted on the antifungal sensitivity of the isolates from 1992 to 2004 and 2005 to 2019.Conclusions: Fonsecaea pedrosoi was the commonest causative agent causing chromoblastomycosis in the studied population. Posaconazole demonstrated the lowest MIC values for the tested isolates followed by itraconazole and voriconazole. Amphotericin B demonstrated very high MIC values which were likely to result in clinical failure upon treatment. MIC values demonstrated minimal fluctuations throughout the tested time.