Wound swabs versus biopsies to detect methicillin resistant Staphylococcus aureus in experimental equine wounds.
Authors: Brock Abbi K, Chamoun-Emanuelli Ana M, Howard Emily A, Huntzinger Katie D, Lawhon Sara D, Bryan Laura K, Cosgriff-Hernandez Elizabeth M, Cohen Noah D, Whitfield-Cargile Canaan M
Journal: Veterinary surgery : VS
Summary
# Wound Sampling Techniques for MRSA Detection in Equine Wounds When managing equine wounds with suspected methicillin-resistant *Staphylococcus aureus* (MRSA) infection, the sampling method used can significantly influence diagnostic outcomes—a distinction that this 2022 experimental study sought to clarify. Researchers inoculated full-thickness skin wounds in three horses with varying concentrations of MRSA, then compared bacterial recovery using surface swabs (Levine technique) versus 3 mm tissue biopsies at 2, 7, 14 and 21 days post-inoculation. Whilst overall bacterial load and species diversity were comparable between the two techniques (moderate correlation of R = 0.49), tissue biopsies detected MRSA substantially more reliably, isolating the organism in 79% of samples compared to only 62% from surface swabs, with fair agreement (κ = 0.31) between methods. The findings suggest that clinicians prioritising MRSA detection in equine wounds—particularly where treatment decisions hinge on confirmatory culture—should favour tissue biopsy sampling over the more commonly used surface swab technique, despite the additional invasiveness. For farriers and practitioners working alongside veterinary teams on cases with suspected MRSA, understanding that negative swab results do not definitively exclude the infection may influence recommendations for clinical follow-up and culture confirmation protocols.
Read the full abstract on PubMed
Practical Takeaways
- •When MRSA infection is suspected in equine wounds, tissue biopsies are more reliable than surface swabs for confirming the diagnosis
- •Surface swabs alone may miss MRSA in approximately 17% of infected wounds; biopsy sampling provides higher sensitivity
- •Consider tissue biopsy as the gold standard sampling method for suspected MRSA wounds rather than relying solely on swab culture
Key Findings
- •MRSA was detected significantly more frequently in tissue biopsy cultures (79%) compared to surface swab cultures (62%), P = 0.016
- •Moderate correlation (R = 0.49) existed between bacterial bioburdens from the two sampling techniques
- •Fair agreement (κ = 0.31) was observed between swab and biopsy methods for MRSA identification
- •Bacterial load and diversity profiles were similar between both sampling techniques overall