Methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) for Microsporum canis: A Case Report of Rapid Resolution in Canine Dermatophytosis Original paper
Researched by:
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Karen Pendergrass
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Karen Pendergrass
Read MoreKaren 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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Kimberly Eyer
Read MoreKimberly Eyer, a Registered Nurse with 30 years of nursing experience across diverse settings, including Home Health, ICU, Operating Room Nursing, and Research. Her roles have encompassed Operating Room Nurse, RN First Assistant, and Acting Director of a Same Day Surgery Center. Her specialty areas include Adult Cardiac Surgery, Congenital Cardiac Surgery, Vascular Surgery, and Neurosurgery.
Researched by:
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Karen Pendergrass
ID
Karen Pendergrass
Read More
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 study investigated the clinical efficacy of methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) for the treatment of dermatophytosis in a dog infected with Microsporum canis. The therapy involves applying methylene blue (a photosensitizer) followed by red light exposure, producing reactive oxygen species (ROS) that inactivate fungal pathogens. The goal was to assess whether MB-APDT could achieve complete clinical cure with minimal recurrence, offering an alternative to long-term antifungal regimens commonly used in veterinary dermatophytosis treatment. The study builds on prior evidence of MB-APDT’s broad-spectrum antifungal activity but represents the first known report of its use specifically for M. canis-induced ringworm in a companion animal.
Who was studied?
The subject was a single 7-year-old male dog diagnosed with dermatophytosis caused by Microsporum canis. Diagnosis was confirmed clinically and mycologically. Two sessions of MB-APDT were administered topically over affected skin lesions, spaced seven days apart. The outcome was monitored for a total of six months post-treatment, with evaluation based on clinical appearance and recurrence status.
Most important findings
The dog achieved complete clinical cure within 21 days, with no reported recurrence after a 6-month follow-up. The MB-APDT treatment caused no adverse effects and required only two topical applications, suggesting rapid fungal inactivation. The antifungal action likely stems from methylene blue’s generation of ROS upon red-light activation, which damages fungal cells through oxidative stress, effectively targeting both M. canis hyphae and spores. This case indicates that Methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) could be a promising short-course therapy to manage dermatophytosis and reduce zoonotic risk.
MB-APDT may also disrupt the fungal microbiome at the skin surface without selecting for resistance, unlike conventional antifungals. While the study did not explicitly assess microbiome modulation, the mechanism of action—non-specific oxidative damage—suggests it could preserve commensal balance better than systemic drugs. This aligns with an antimicrobial stewardship approach and may be beneficial in microbiome-sensitive veterinary dermatology.
Key implications
This case study introduces Methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) as a novel, fast-acting, non-invasive treatment for dermatophytosis caused by Microsporum canis in pets, with potential translational value in human medicine and veterinary dermatology. Its dual advantages—fungal eradication and minimal treatment duration—address major challenges in managing M. canis, especially given its zoonotic potential and environmental persistence. MB-APDT’s mechanism circumvents drug resistance and may preserve the host skin microbiome, making it an attractive alternative to prolonged topical or systemic antifungal use. Future studies should include larger controlled trials to confirm efficacy, assess microbiome shifts, and define optimized treatment protocols across species.