Microsporum canis Antifungal Resistance Confirmed by PCR and Susceptibility Testing Original paper
Researched by:
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Karen Pendergrass
ID
Karen Pendergrass
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease—four years before the first published case study.
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Karen Pendergrass
Researched by:
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Karen Pendergrass
ID
Karen Pendergrass
Microbiome Signatures identifies and validates condition-specific microbiome shifts and interventions to accelerate clinical translation. Our multidisciplinary team supports clinicians, researchers, and innovators in turning microbiome science into actionable medicine.
Karen Pendergrass
What was studied?
This case report investigated the molecular detection and antifungal susceptibility of Microsporum canis (M. canis), focusing on microsporum canis antifungal resistance, a zoophilic dermatophyte commonly implicated in feline ringworm, with zoonotic potential. The primary objective was to confirm M. canis from infected cats using both phenotypic and molecular methods and to assess its in vitro susceptibility to six antifungal agents. After clinical identification of ringworm-like lesions in a mother cat and five kittens, samples were cultured on Sabouraud Dextrose Agar (SDA) and Dermatophyte Test Medium (DTM), stained with lactophenol cotton blue, and examined microscopically. Molecular confirmation was achieved through PCR targeting a specific 180 bp region of the ITS1 ribosomal DNA cassette. An antifungal susceptibility test using the disc diffusion method evaluated the efficacy of amphotericin-B, clotrimazole, fluconazole, itraconazole, ketoconazole, and miconazole.
Who was studied?
The subjects were one adult female cat and five kittens presented to a veterinary clinical complex in Madhya Pradesh, India. All animals exhibited signs of dermatophytosis, including pruritus, erythema, and alopecia. Microsporum canis antifungal resistance was a concern due to the clinical lesions on the animals and the zoonotic transfer to the human owner. Fungal isolates were obtained from skin scrapings and processed using both culture-based and molecular diagnostics to confirm the presence of M. canis.
Most important findings
The study confirmed M. canis through macroscopic and microscopic features, including spindle-shaped macroconidia and colony morphology on SDA and DTM. PCR validation identified the expected 180 bp band specific to M. canis. Antifungal susceptibility testing revealed multidrug resistance, with resistance or intermediate sensitivity to five of six antifungal agents. The issue of microsporum canis antifungal resistance was crucial as only itraconazole demonstrated definitive sensitivity.
| Antifungal Agent | Zone of Inhibition (mm) | Interpretation |
|---|---|---|
| Fluconazole (25µg) | 0 | Resistant |
| Amphotericin-B (50µg) | 17 | Sensitive |
| Clotrimazole (10µg) | 16 | Intermediate |
| Itraconazole (10µg) | 21 | Sensitive |
| Ketoconazole (10µg) | 5 | Resistant |
| Miconazole (30µg) | 15 | Intermediate |
These findings align with prior data highlighting itraconazole’s superior antifungal efficacy against M. canis, though microsporum canis antifungal resistance profiles are becoming increasingly variable across studies.
Key implications
The study underscores the increasing problem of microsporum canis antifungal resistance in M. canis, which poses a serious threat to both veterinary and public health. The demonstrated multidrug resistance, particularly to commonly used azoles like fluconazole and ketoconazole, necessitates molecular confirmation and susceptibility testing prior to treatment. Itraconazole emerged as the most effective agent in this case, suggesting its preferred use in resistant feline dermatophytosis. Moreover, the zoonotic transmission observed reinforces the need for rapid diagnostics and cross-species surveillance. From a microbiome perspective, understanding the ecology of M. canis and its antifungal resistance may have broader implications for microbial competition and skin microbiota dysbiosis in both animals and humans.