The antimicrobial activity of bupivacaine, lidocaine and mepivacaine against equine pathogens: An investigation of 40 bacterial isolates.
Authors: Adler D M T, Damborg P, Verwilghen D R
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Local anaesthetic injections form an essential diagnostic tool in equine lameness investigations, yet the procedural breach of tissue barriers creates iatrogenic infection risk. Researchers at this institution evaluated whether three commonly used local anaesthetics—bupivacaine, lidocaine and mepivacaine—possessed inherent antimicrobial properties against 40 clinically isolated equine pathogens (spanning eight genera including Staphylococcus, Streptococcus, Pseudomonas and Rhodococcus) using broth microdilution methodology to determine minimum inhibitory and bactericidal concentrations. At clinically applied concentrations, bupivacaine and lidocaine inhibited growth in 93% of isolates tested with bactericidal activity in approximately 80% of those cases, whilst mepivacaine achieved 80% growth inhibition with similar bactericidal efficacy—a reassuring finding suggesting some inherent protective capacity. Nevertheless, these results should not diminish commitment to rigorous aseptic technique and antiseptic skin preparation, as the antimicrobial effect, whilst notable in vitro, may prove insufficient to prevent infection in the immunologically complex environment of synovial spaces and periarticular soft tissues, where local inoculum and host factors substantially influence clinical outcomes. This work provides a useful baseline for understanding the pharmacological profile of these agents, but practitioners should continue treating them as analgesics and diagnostics rather than antimicrobial safeguards.
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Practical Takeaways
- •Local anaesthetics provide some inherent protection against bacterial inoculation during joint and soft tissue injections, but this should not replace rigorous aseptic preparation
- •Bupivacaine and lidocaine offer slightly better antimicrobial coverage than mepivacaine at clinical concentrations
- •While this study is reassuring about antimicrobial activity at injection sites, strict sterile technique and proper skin disinfection remain the gold standard for preventing injection-related infections
Key Findings
- •Bupivacaine and lidocaine at clinical concentrations inhibited growth in 93% of equine bacterial isolates, while mepivacaine inhibited 80%
- •For 80% of inhibited isolates, the local anaesthetic concentrations were bactericidal rather than merely bacteriostatic
- •Tested local anaesthetics showed antimicrobial activity against 8 bacterial genera commonly isolated from equine infections (Actinobacillus, Corynebacterium, Enterobacter, Escherichia, Pseudomonas, Rhodococcus, Staphylococcus, Streptococcus)
- •Despite antimicrobial properties, aseptic technique and antiseptic preparation remain essential before local anaesthetic injections