Reframing Dermatophytosis: An Emerging Challenge in Infectious Disease Diagnostics
Superficial fungal infections caused by dermatophytes remain among the most prevalent yet under-prioritized threats in public health and veterinary medicine. According to the World Health Organization, dermatophytosis affects over 20% of the global population at any given time, with higher incidence rates in tropical climates and in settings with poor hygiene, overcrowding, or close animal contact. While often considered a minor ailment, the growing resistance to antifungal agents and the emergence of new species have escalated these infections into a complex diagnostic and therapeutic challenge.
These filamentous fungi, traditionally identified via classical morphological and culture-based methods, are now exhibiting an alarming pace of genetic evolution and antifungal resistance—dynamics that increasingly render conventional diagnostics inadequate. Clinical laboratories across the globe are observing a rise in misidentification, therapeutic misalignment, and diagnostic ambiguity, particularly in complex or polymicrobial presentations.
At the forefront of efforts to recalibrate fungal diagnostics is Varsha Garg, staff scientist at Charité Universitätsmedizin in Berlin, in the research group of Prof. Dr. Yvonne Gräser, who leads the national reference laboratory for dermatophytes. In collaboration with Xpedite Diagnostics, lead by Dr. Johannes Gräf and Dr. Andy Wende, and ANCHOR Diagnostics, lead by Dr. Rainer Söller in Hamburg, Varsha is contributing to a project aimed at developing a novel dermatophyte assay for rapid multiplex PCR, designed to deliver fast and precise species-level molecular identification. Her transition from plant molecular biology to infectious disease diagnostics underscores a broader pivot toward translational applications with immediate clinical and public health relevance.
“Dermatophytes are not static taxonomic entries, they’re dynamic biological systems. Their genome shifts, and so must our ability to diagnose,” Varsha explains. “If we don’t keep pace, we misidentify, mistreat, and miss opportunities to contain transmission.”
By embedding molecular diagnostics into frontline workflows, Varsha’s work aims to reduce diagnostic latency, increase specificity, and ultimately improve patient outcomes in veterinary contexts.
Development of a High-Sensitivity, Species-Specific qPCR Workflow for Dermatophyte Detection
With support from Xpedite Diagnostics on the sample preparation workflow, the team is developing a rapid modular based detection pipeline aimed at reducing the time-to-result to less than a couple of hours. The pipeline is focused on the detection of zoophilic dermatophytes and it integrates:
- Sample Acquisition – Including keratinized tissues such as skin, claws, and hair.
- DNA Extraction – Utilizing optimized lysis buffers and protocols co-developed with Xpedite, capable of overcoming the challenges of hard tissues such as claws and nails.
- Geometrical Multiplex qPCR Amplification – Co-developed with ANCHOR Diagnostics, Incorporating species-specific primer/probe sets that target genomic regions with high discriminatory power, even among phylogenetically close taxa.
- Clinical Interpretation – Enabling informed therapeutic interventions by correlating species identification with antifungal susceptibility profiles.
The detection system’s functionality has been demonstrated at copy numbers as low as 10 using artificially developed positive control DNA stretches; however, the validation with low-titer infections or single-copy presence in real samples is under consideration. Moreover, thevalidation studies of different modules will be conducted on a wide variety of sample types.
“We’re designing for both sensitivity and specificity,” says Varsha. “Our primers need to distinguish between nearly identical dermatophyte genomes, because even slight misidentification can lead to ineffective treatment.”
Technical and Operational Barriers in Current Dermatophyte Diagnostic Workflows
Several major challenges hinder effective diagnosis and containment of dermatophyte infections:
- Genomic homogeneity: Closely related zoophilic dermatophyte species such as Trichophyton mentagrophytes and Trichophyton quinckeanum exhibit>98% similarity in conserved gene regions, making molecular differentiation difficult without high-resolution techniques.
- Antifungal resistance: Terbinafine resistance has become a critical issue, especially in strains circulating in India and Southeast Asia. Mutations in the SQLE gene have been linked to treatment failure.
- Sample quality: Poorly collected or processed samples often contain low DNA yield or inhibitors that interfere with amplification, particularly in keratinized material like nails.
- Zoonotic transmission: Species belonging to the genera Trichophyton such as T.mentagrophytes are highly transmissible between pets and humans, especially in densely populated urban environments. Yet veterinary diagnostics remain fragmented.
- Slow turnaround time: Culture-based identification typically takes 7–21 days and is further complicated by contamination or non-viable organisms.
These problems call for a rethinking of both laboratory workflows and field protocols.
Advancing One Health Surveillance Through Integrated Veterinary Diagnostic Platforms
Veterinary dermatophytosis is often underreported, despite being a reservoir for zoonotic transmission. Dogs and cats, particularly in shelters or rural environments, may carry infections asymptomatically, shedding spores that persist for months. To address this, Prof. Gräser team is developing a diagnostic panel that can accommodate:
- Hair, claw, and skin samples from multiple species
- Environmental surface testing for fungal contamination
- Low-cost protocols for animal health NGOs and field clinics
The aim is to integrate this data with animal diagnostic networks, enabling real-time zoonotic tracking across species boundaries, a core principle of the One Health framework.
Phenotypic Plasticity in Dermatophyte Cultures and Its Diagnostic Implications
Despite the push toward molecular diagnostics, Varsha maintains a healthy respect for classical microbiology.
“You’ll plate a genetically identical strain twice and end up with two morphologically different colonies. This is quite fascinating and intriguing.”
These observations suggest that dermatophyte expression may be influenced by epigenetics, microenvironment, or metabolic plasticity, opening up new questions for research and diagnostics alike.
Fungal Genomic Surveillance and Resistance Tracking in Dermatophyte Epidemiology
In 2017, researchers in India documented a new strain of Trichophyton mentagrophytes, Type VIII, showing mutations in both ITS and β-tubulin gene regions. This strain was linked to widespread terbinafine resistance and atypical deep-skin infections. Similar anomalies are now being reported in parts of the Middle East, North Africa, and Eastern Europe.
The challenge lies in tracking these strains in real time. Without genomic surveillance and accessible diagnostics, resistance trends remain invisible until widespread treatment failure occurs.
To address this, the reference laboratory is collaborating with regional laboratories, hospitals and dermatologists and has established a dermatophyte resistance database. This includes curated sequence variants of common resistance gene (SQLE).
Toward Next-Generation Diagnostic Systems for Real-Time Dermatophyte Monitoring
To combat the evolving dermatophyte landscape, diagnostic systems must be:
- Portable – Deployed in rural clinics, shelters, and field stations
- Multiplexed – Capable of detecting species, resistance markers, and potential co-infections
- Rapid – Delivering results within 60 minutes from raw sample to interpretation
- Interoperable – Feeding into surveillance networks for zoonotic and antimicrobial resistance trends
Artificial intelligence and machine learning will also play a role. Future systems could integrate image recognition of culture morphologies with molecular signals and clinical metadata to automate species-level diagnosis with minimal user input.
“We’re not just building molecular tests, we’re building a diagnostic infrastructure for faster and more insightful fungal epidemiology” says Varsha.
Explore Further
- More resources: "Faster, Cleaner, Simpler Reverse-Purification Fungal DNA Extraction Workflow for Keratinized Samples"
- Contact us to learn more and collaborate on fungal diagnostics.