Staphylococcus aureus and Nasal Colonization in Horses

The significance of this finding is unknown but should be a reminder that following interactions with your horse, you should wash your hands. Particular care should be followed if you have a healing wound or are immune compromised. I recommend using a regular soap and avoid antibacterial products as such products may actually promote pathogens by reducing the normal, healthy bacterial flora on the skin.
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Prevalence and Risk Factors of Staphylococcus aureus Nasal Colonization in Horses Admitted to a Veterinary Teaching Hospital
J Vet Intern Med. 2025 May-Jun;39(3):e70027. doi: 10.1111/jvim.70027.
Authors
Marion Allano 1 , Julie Arsenault 2 , Marie Archambault 1 3 , Julie-Hélène Fairbrother 3 , Frédéric Sauvé 1
Affiliations

1 Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.
2 Research Chair in Antimicrobial Surveillance and Antimicrobial Resistance in Animal Health, Epidemiology of Zoonoses and Public Health Research Unit (GREZOSP) and Department of Pathology and Microbiology, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.
3 Bacteriology Diagnostic Laboratory, Complexe de Diagnostic et d’Épidémiosurveillance Vétérinaires du Québec, Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec and Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Canada.

PMID: 40135807
DOI: 10.1111/jvim.70027

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections, including in veterinary settings.

Hypothesis/objectives: To investigate the prevalence, risk factors for Staphylococcus aureus (SA) and MRSA colonization, and the duration of MRSA colonization.

Animals: Elective cases admitted to the Veterinary Teaching Hospital were recruited (228 horses).

Methods: A cross-sectional study was conducted over 3 years. Nasal swabs were collected at admission and cultured for SA. Methicillin-resistant isolates were identified using matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) technology, oxacillin minimal inhibitory concentration (MIC), and PCR testing. Horses colonized with MRSA were resampled until two negative cultures were obtained. Stabling management, activity, and medical history were obtained from owners and medical files. Multivariable logistic regressions were used to model associations between risk factors and colonization.

Results: The prevalence of SA and of MRSA nasal carriage was 17.5% (95% CI: 12.4-22.7) and 6.2% (95% CI: 2.9-9.4), respectively. Of the 10 horses colonized by MRSA and monitored over time, only one tested positive after 3 months. More than 10 horses on the premises (OR 6.0 – 95% CI 1.1-64.2), previous hospitalization (OR 6.0 – 95% CI 1.0-35.2), and year of admission (2022 vs. 2020-2021; OR 9.0 – 95% CI 1.7-92.2) were associated with MRSA nasal carriage.

Conclusions and clinical importance: The prevalence of MRSA nasal colonization is of concern; however, the carriage seems transitory. Apart from the medical risk factors, the importance of social interactions in MRSA transmission needs to be elucidated in horses.

Keywords: MRSA; antimicrobial resistance; epidemiology; equine; infection control; nosocomial.

© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.