Study Finds Dog Ear Infections Linked to Antifungal Resistance

Mutations in a key protein make a yeast found in dogs more resistant to common topical treatments.

Apr. 8, 2026 at 9:32am

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An extreme close-up X-ray photograph showing the translucent, ghostly structures of fungal yeast cells within a dog's ear canal, conceptually illustrating the genetic resistance mechanisms behind recurring ear infections.An X-ray view into the inner workings of a dog's ear canal reveals the resistant fungal yeast strains behind persistent ear infections.Champaign Today

Researchers at the University of Illinois Urbana-Champaign have found that mutations in a key protein make a yeast commonly found in dogs with outer ear infections more resistant to the topical antifungals used to treat it. The study involved isolating clinical yeast samples from dogs with recurrent ear infections, analyzing their DNA sequences and protein structures, and investigating how the structure of the target protein affects its interaction with various antifungal drugs.

Why it matters

This research provides important insights into the growing problem of antifungal resistance in veterinary medicine, which can lead to chronic, difficult-to-treat ear infections in dogs. Understanding the genetic and structural factors behind this resistance will help veterinarians optimize the use of existing antifungal drugs and develop new treatment strategies to maintain their effectiveness.

The details

The researchers isolated yeast samples from dogs with recurrent ear infections and found they clustered into three distinct groups based on DNA sequencing. They then focused on the ERG11 gene, which encodes a critical protein in the yeast cell membrane that is the target of commonly prescribed azole antifungals. They identified mutations in the ERG11 gene that altered the structure of the Erg11 protein, preventing the antifungal drugs from effectively binding to it. This explained why some yeast strains were resistant to miconazole, the first-line topical treatment. The researchers also found that posaconazole, a longer-tailed azole, was more effective against the resistant strains due to its increased contact points with the altered Erg11 protein.

  • The study was conducted in 2026 at the University of Illinois Urbana-Champaign.
  • The researchers collected the yeast samples from dogs with recurrent ear infections in the clinic.

The players

Lois Hoyer

A professor of pathobiology at the University of Illinois Urbana-Champaign who designed the study and analyzed the yeast samples.

Clarissa Pimentel de Souza

A clinician and professor of dermatology and otology in the University of Illinois College of Veterinary Medicine who noticed an increase in persistent fungal ear infections in her patients and collaborated on the study.

Chien-Che Hung

A clinical professor and veterinary microbiologist who isolated the yeast samples in pure culture for the study.

Cole Belcher

A graduate student who analyzed the cultured yeast samples with Hoyer.

Joel Tyndall

A pharmacy professor at the University of Otago in New Zealand who collaborated with the Illinois team to investigate how the structure of the Erg11 protein affected its interaction with antifungal drugs.

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What they’re saying

“A common situation seen in practice is the use of an antifungal to treat recurrent yeast otitis externa, without addressing the underlying allergies driving the infection. If the primary allergic disease is not concurrently worked up, the dog will develop another infection shortly after the discontinuation of the topical antifungal. This situation leads to the chronic use of antifungals in the ears, which can be a risk factor for developing resistance.”

— Clarissa Pimentel de Souza, Clinician and professor of dermatology and otology

“We first wanted to understand better how the yeasts are related to each other. We did some DNA sequencing, and we made a tree. We found they cluster into three groups.”

— Lois Hoyer, Professor of pathobiology

“The most common topical antifungal treatments prescribed are azoles, and miconazole is the first line of defense. If the resistance is caused by a gene mutation altering the structure of the target protein, the antifungal cannot bind to it and will not kill the yeast.”

— Clarissa Pimentel de Souza, Clinician and professor of dermatology and otology

What’s next

The researchers plan to study the miconazole-resistant yeast isolates further to understand their interactions with longer-tailed azole antifungals. They also intend to collect and culture more yeast samples that are likely to be resistant to treatment in order to test them against multiple drugs and associate the DNA sequence changes with the drug resistance results.

The takeaway

This study provides critical insights into the growing problem of antifungal resistance in veterinary medicine, which can lead to chronic and difficult-to-treat ear infections in dogs. By understanding the genetic and structural factors behind this resistance, veterinarians can optimize the use of existing antifungal drugs and develop new treatment strategies to maintain their effectiveness and prevent the further spread of resistant yeast strains.