Antifungal susceptibility testing of Microsporum canis isolated from the skin of dermatologically healthy cats.

BACKGROUND

Dermatophytes are fungi that invade keratinized tissues, causing superficial skin lesions in both animals and humans. Although Microsporum canis (M. canis) is the most frequent dermatophyte in companion animals, and cats are considered carriers and disseminators, few reports have determined its prevalence and antifungal susceptibility in healthy cats, which could represent a public health problem.

AIM: This study aimed to determine the prevalence and antifungal susceptibility of dermatophyte strains obtained from dermatologically healthy cats in the city of Talca, Chile.

METHODS

From March 2024 to August 2024, skin or hair samples were collected from three anatomical zones (facial, abdomen, and limbs) of 113 dermatologically healthy cats using the mat technique. Samples were seeded in Sabouraud dextrose agar enriched with chloramphenicol plus cycloheximide and incubated at 25ºC for 21 days. Then, the antifungal sensitivity of the isolated strains was determined by disc diffusion testing, and amphotericin B (10 µg), fluconazole (25 µg), clotrimazole (10 µg), caspofungin (5 µg), voriconazole (1 µg), and nystatin (100 µg) were used as antifungals. The chi-square independence test (p < 0.05) was used to determine the association between the anatomical site of the sample and isolation of dermatophytes, as well as between dermatophyte carriage and the epidemiological variables of the study population.

RESULTS

Of the 113 healthy cats included in this study, six (5.3%) were found to be fungal carriers, with M. canis being the only isolated dermatophyte species. While 100% of the strains were susceptible to clotrimazole, voriconazole, caspofungin, amphotericin B, and nystatin, all were fluconazole-resistant. Confinement status was the only epidemiological variable associated with fungal carriage (p = 0.009), with indoor cats having a 10.73-fold greater risk of carrying dermatophytes than outdoor cats. No association was found between the anatomical site and the isolation of dermatophytes.

CONCLUSION

Microsporum canis was the only dermatophyte isolated from the skin and hair of dermatologically healthy cats in Talca, with a prevalence of 5.3%. All the isolates were fluconazole-resistant.