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

Summary

Researchers in Thailand studied a fungal infection called sporotrichosis that affects both cats and people. They used advanced DNA sequencing technology to identify the specific type of fungus and understand how it’s related to similar fungi found in other parts of the world. They also tested how well common antifungal medications work against these fungi and found that some isolates are becoming harder to treat.

Background

Sporothrix spp. are dimorphic fungi that cause sporotrichosis, ranging from local skin infections to systemic disease. Species identification is challenging due to morphological similarity, requiring molecular techniques using barcoding genes such as the ITS region and calmodulin gene for accurate classification.

Objective

This study evaluated the ability of 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 of the isolates to commonly used antifungal agents.

Results

ONT sequencing of calmodulin successfully identified all isolates as S. schenckii sensu stricto with 99-100% identity, while ITS showed lower discriminatory power. Phylogenetic analysis revealed all isolates clustered in a specific Southeast Asian subclade of S. schenckii sensu stricto. Eight out of 26 isolates (31%) exhibited elevated itraconazole MICs (>2 µg/mL), with MIC ranges of 0.06-8 µg/mL.

Conclusion

ONT sequencing of the calmodulin gene provides accurate species identification and phylogenetic classification comparable to Sanger sequencing, offering advantages for high-throughput analysis. The presence of elevated itraconazole MICs in some Thai isolates highlights concerning trends in antifungal resistance that warrant continued surveillance and investigation of optimal treatment strategies.
  • Published in:PLoS Neglected Tropical Diseases,
  • Study Type:Molecular Epidemiological Study,
  • Source: 10.1371/journal.pntd.0013253, PMID: 40587582
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