Retrospective multicentre study of methicillin-resistant Staphylococcus aureus infections in 115 horses.
Authors: Anderson M E C, Lefebvre S L, Rankin S C, Aceto H, Morley P S, Caron J P, Welsh R D, Holbrook T C, Moore B, Taylor D R, Weese J S
Journal: Equine veterinary journal
Summary
# Editorial Summary: MRSA Infections in Horses — A Six-Year Multicentre Review Between 2000 and 2006, researchers across six veterinary teaching hospitals in Canada and the USA collated clinical data on 115 horses with confirmed methicillin-resistant *Staphylococcus aureus* (MRSA) infections to characterise the disease patterns, risk factors and outcomes in equine populations. Community-acquired and hospital-acquired MRSA infections occurred with near-equal frequency (49.1% and 50.9% respectively), with surgical site infections representing the most common clinical presentation at 38%, whilst the remaining cases involved respiratory, soft tissue and other systemic infections. Survival to discharge was encouraging overall at 83.8%, though factors significantly predicting poor outcome included intravenous catheterisation, community-acquired infection source, and infection dissemination beyond the primary site; hospital-acquired infections were notably associated with previous hospitalisation and gentamicin exposure. For equine practitioners, these findings suggest that MRSA should be considered an opportunistic pathogen with a favourable prognosis in most cases, yet heightened vigilance is warranted when managing post-operative wounds, managing systemic infections in previously hospitalised animals, and carefully weighing antimicrobial choices — particularly given the gentamicin association with community-acquired disease.
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Practical Takeaways
- •MRSA infections in horses are opportunistic and carry a relatively good prognosis (84% survival), but complications from disseminated infection and IV catheterization significantly worsen outcomes
- •Surgical incision management is critical as this was the most common infection site; practitioners should maintain vigilant wound care protocols in hospitalized horses
- •Community-associated MRSA is equally prevalent as hospital-associated cases, suggesting vigilance for MRSA risk is needed in both settings, particularly in previously hospitalized horses
Key Findings
- •Hospital-associated and community-associated MRSA infections were equally common (50.9% vs 49.1%) in 115 hospitalized horses
- •Surgical incision infection was the most frequent clinical presentation (38.0% of cases)
- •Overall survival to discharge was 83.8%, with nonsurvival associated with intravenous catheterization, CA-MRSA infection, and disseminated infection
- •Previous hospitalization and gentamicin treatment were significant risk factors for CA-MRSA, while infected incision sites were associated with HA-MRSA