Abstract

Background:
Otitis frequently affects dogs. Underlying diseases and predisposing factors affect the otic environment, thereby causing bacterial proliferation. One of the most isolated species in cases of otitis is the Staphylococcus genus, which has widely reported antimicrobial resistance profiles. This has not yet been studied in Talca, Chile.

Aim:
The objective of this study was to determine the existence of antimicrobial resistance in Staphylococcus strains isolated from the external auditory canal of a group of dogs diagnosed with otitis externa in Talca, Chile.

Methods:
Samples were taken from the external ear canal of 20 dogs with otitis externa from October 2023 to August 2024 at dermatological consultations in the city of Talca. The samples were transported to be processed and analyzed in the MICROVET Veterinary Microbiology laboratory, of the Faculty of Veterinary and Livestock Sciences of the University of Chile, using VITEK® 2 equipment for the identification and determination of antimicrobial susceptibility. The association between the epidemiological variables of the patients and the antimicrobial susceptibility of Staphylococcus strains was determined.

Results:
Staphylococcus spp. isolation was obtained in 8 samples, 62.5% of which were strains of the CPS group, of which 25% were identified as S. aureus and 37.5% as S. pseudintermedius. The remaining 37.5% were CoNS strains, which were identified as S. chromogenes (12.5%), S. simulans (12.5%), and S. lentus (12.5%). The 50 % of the isolates were resistant, with S. pseudintermedius being multidrug-resistant (MDR), with resistance to 6 antibiotics and S. lentus resistant to 5, both of which were also methicillin-resistant (MRS). There was no association between the epidemiological variables of the patients and the antimicrobial susceptibility of the Staphylococcus strains.

Conclusion:
These preliminary results are the first report in Chile demonstrating the presence of methicillin-resistant Staphylococcus in a group of dogs with otitis externa in Talca, Chile, South America using VITEK®. These results are relevant from a public health perspective given the close contact between owners, veterinarians, and dogs with otitis externa. These preliminary data contribute to the local understanding of this global phenomenon and provide information to support the theoretical framework for future local studies on epidemiological surveillance.

Key words: Antimicrobial resistance, Dog, otitis externa, Staphylococcus