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Dual-Emission FRET-PCR Outperforms SYBR Green and EvaGreen for Accurate Discrimination of Primary Canine Dermatophytes: Microsporum canis, Nannizzia gypsea, and Trichophyton mentagrophytes

Summary

Dogs often get fungal skin infections caused by three main types of fungi. Doctors have traditionally grown these fungi in culture, which takes 2-4 weeks. Scientists have now developed a faster genetic test called FRET-PCR that can identify which fungus is causing the infection in just 2.5 hours. This new test is more accurate and reliable than older genetic tests, helping veterinarians treat infections quickly and prevent them from spreading.

Background

Dermatophytosis is a contagious fungal infection in dogs caused primarily by three species: Microsporum canis, Nannizzia gypsea, and Trichophyton mentagrophytes. Conventional diagnosis using fungal culture and microscopy is time-consuming, taking 2-4 weeks, and often lacks sensitivity. Accurate species identification is essential for guiding treatment, limiting transmission, and epidemiological surveillance due to the distinct transmission routes and zoonotic potential of each species.

Objective

To develop and compare three real-time PCR platforms (SYBR Green, EvaGreen, and dual-emission FRET) targeting the chitin synthase 1 gene for simultaneous detection and differentiation of the three major canine dermatophytes. The study aimed to evaluate sensitivity, specificity, and species discrimination capability of each platform.

Results

FRET-based qPCR demonstrated superior performance with 100% specificity and a detection limit of single gene copy per reaction, with distinct melting profiles (M. canis ~56.1°C, N. gypsea ~53.0°C, T. mentagrophytes ~51.8°C). SYBR Green and EvaGreen assays showed reduced sensitivity at low template concentrations and cross-reactivity with non-target fungi. FRET-qPCR correctly identified all ATCC reference strains and clinical isolates without false positives.

Conclusion

The FRET-based qPCR assay offers a rapid, sensitive, and specific method for species-level identification of primary canine dermatophytes with results in 2.5 hours versus 2-4 weeks for culture. The superior performance over dye-based systems makes it well-suited for clinical implementation and molecular surveillance. Its tolerance for low DNA inputs and high specificity provide significant advantages for timely diagnosis and improved treatment outcomes.
  • Published in:Journal of Fungi,
  • Study Type:Comparative Analytical Study,
  • Source: PMID: 41149898, DOI: 10.3390/jof11100708
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