Targeted long-read sequencing analysis and antifungal susceptibility profiles of Sporothrix schenckii isolates from Thailand

Author: mycolabadmin
6/30/2025
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Summary

Researchers in Thailand studied a fungal infection called sporotrichosis by using advanced DNA sequencing technology to identify the exact species and understand how different strains are related to each other. They found that while current treatment options work, some strains are becoming resistant to the main drug used (itraconazole). The study shows that a newer, faster DNA sequencing method can be just as reliable as traditional methods for identifying these dangerous fungi and tracking how they spread between cats and humans.

Background

Sporothrix species are dimorphic fungi causing sporotrichosis that ranges from local skin infections to systemic infections in immunocompromised individuals. Accurate species identification requires molecular techniques as morphological similarity makes microscopy insufficient. The calmodulin gene offers higher phylogenetic resolution than the commonly used ITS region for Sporothrix species classification.

Objective

This study evaluated Oxford Nanopore Technology (ONT) long-read sequencing of calmodulin and ITS regions to identify Sporothrix species and perform phylogenetic analysis of isolates from humans and felines in Thailand. The study also assessed antifungal susceptibility profiles and compared clustering methods to improve species identification accuracy.

Results

ONT sequencing of calmodulin identified all 26 isolates as S. schenckii sensu stricto with 99-100% identity, while ITS showed lower discriminatory power. Phylogenetic analysis revealed all isolates clustered in subclade I with geographic association to Southeast Asia. Eight out of 26 isolates (31%) demonstrated elevated itraconazole MICs (>2 µg/mL), with elevated fluconazole MICs observed in most isolates.

Conclusion

ONT sequencing of calmodulin allows accurate species identification and phylogenetic analysis of S. schenckii sensu stricto isolates comparable to Sanger sequencing. The UMAP-HDBSCAN clustering method effectively reduces technical errors in long-read analysis. The findings highlight growing concern regarding elevated itraconazole MICs in Southeast Asian isolates, emphasizing the need for ongoing antifungal susceptibility surveillance.

Published in:PLoS Neglected Tropical Diseases,
Study Type:Original Research,
Source: PMID: 40587582, DOI: 10.1371/journal.pntd.0013253