Prevalence and Risk Factors of Staphylococcus aureus Nasal Colonization in Horses Admitted to a Veterinary Teaching Hospital.
Authors: Allano Marion, Arsenault Julie, Archambault Marie, Fairbrother Julie-Hélène, Sauvé Frédéric
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Staphylococcus aureus nasal colonisation poses a genuine infection control concern in equine hospital settings, particularly methicillin-resistant strains (MRSA), which can trigger nosocomial disease outbreaks. Researchers recruited 228 horses admitted for elective procedures to a teaching hospital over three years, collecting nasal swabs at admission and culturing them using MALDI-TOF mass spectrometry, oxacillin MIC testing, and PCR to identify both *S. aureus* and MRSA isolates; animals harbouring MRSA were resampled longitudinally until two consecutive negative cultures were obtained. Nasal carriage of *S. aureus* overall affected 17.5% of admissions, with MRSA accounting for 6.2%—a notable prevalence—though reassuringly, only one of ten monitored MRSA-positive horses remained colonised after three months, suggesting transient rather than persistent carriage. Critical risk factors included premises housing more than ten horses (OR 6.0), prior hospitalisation (OR 6.0), and year of admission in 2022 versus 2020–2021 (OR 9.0), implicating both direct hospital exposure and broader management density in transmission dynamics. The findings highlight that infection control protocols should address both individual medical history and herd-level social mixing, though the transitory nature of colonisation offers some reassurance regarding long-term carriage burden in previously exposed individuals.
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Practical Takeaways
- •Screen horses at admission to teaching hospitals and high-density facilities for MRSA carriage to implement infection control measures and reduce nosocomial transmission
- •Horses with previous hospitalization or housed with >10 other horses carry elevated MRSA risk; consider enhanced biosecurity protocols for these animals
- •MRSA nasal colonization in horses appears to resolve spontaneously within 3 months in most cases, suggesting colonization may not require prolonged treatment but warrants monitoring
Key Findings
- •SA nasal carriage prevalence was 17.5% (95% CI: 12.4-22.7) and MRSA prevalence was 6.2% (95% CI: 2.9-9.4) in horses admitted to a veterinary teaching hospital
- •MRSA colonization appears transitory, with only 1 of 10 monitored horses testing positive after 3 months
- •More than 10 horses on premises (OR 6.0), previous hospitalization (OR 6.0), and admission year 2022 vs 2020-2021 (OR 9.0) were significant risk factors for MRSA nasal carriage