Methicillin-resistant Staphylococcus aureus in horses at a veterinary teaching hospital: frequency, characterization, and association with clinical disease.
Authors: Weese J S, Rousseau J, Willey B M, Archambault M, McGeer A, Low D E
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Methicillin-resistant *Staphylococcus aureus* (MRSA) represents a genuine concern in equine hospital settings, yet its true prevalence and clinical significance in equine populations remained poorly characterised at the time of this study. Weese and colleagues screened 2,283 horses admitted to Ontario Veterinary College Teaching Hospital using nasal swabs collected at admission, weekly during hospitalisation, and at discharge, identifying MRSA in 120 animals (5.3%). Notably, approximately half of positive cases (50.8%) were already colonised on arrival rather than acquired during hospitalisation, whilst 11.7% of colonised horses subsequently developed clinical MRSA infections—those colonised at admission being 39 times more likely to progress to active disease than non-colonised animals. Antibiotic exposure, specifically ceftiofur or aminoglycosides, emerged as the only significant risk factor for nosocomial colonisation. These findings should prompt farriers, veterinarians, and stable managers to consider MRSA as a potential complication in hospitalised horses and those receiving broad-spectrum antimicrobials, whilst screening protocols may help identify high-risk individuals before they develop costly and treatment-resistant infections.
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Practical Takeaways
- •Implement MRSA screening protocols for horses at admission and during hospitalization to identify colonized animals and reduce nosocomial transmission risk in equine facilities
- •Exercise caution when prescribing ceftiofur or aminoglycosides as these antimicrobials are associated with increased risk of nosocomial MRSA colonization
- •Consider horses colonized with MRSA at admission as high-risk for developing clinical infection and implement appropriate infection control measures and monitoring
Key Findings
- •MRSA was isolated from 5.3% (120/2,283) of horses admitted to a veterinary teaching hospital, with 50.8% colonized at admission and 44.2% acquiring colonization during hospitalization
- •Horses colonized at admission were 38.9 times more likely to develop clinical MRSA infection than non-colonized horses (OR 38.9, 95% CI 9.49-160, P < 0.0001)
- •Clinical MRSA infections developed in 11.7% (14/120) of colonized horses with nosocomial infection incidence of 1.8 per 1,000 admissions
- •Ceftiofur or aminoglycoside administration during hospitalization was the only identified risk factor for nosocomial MRSA colonization