Sequential bacterial sampling of the midline incision in horses undergoing exploratory laparotomy.
Authors: Isgren C M, Salem S E, Townsend N B, Timofte D, Maddox T W, Archer D C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Bacterial Contamination and Surgical Site Infections Following Equine Exploratory Laparotomy Understanding the relationship between bacterial contamination and surgical site infection (SSI) development remains challenging in equine abdominal surgery, despite SSI being a significant complication affecting patient outcomes and economic burden. Isgren and colleagues conducted a prospective cohort study sampling the ventral midline of 31 horses undergoing exploratory laparotomy at multiple time-points—pre-operatively, intra-operatively, and post-operatively—to characterise the bacterial species present and determine whether specific isolates predicted SSI development. Seven horses (22.6%) developed SSI; notably, positive intra-operative cultures were not predictive of infection, and when SSI occurred, the causative organism differed from those identified during surgery, suggesting contamination at laparotomy does not directly translate to later infection. Multi-drug resistant organisms including MRSA and ESBL-producers were isolated post-operatively in five horses total, yet none of these animals developed clinical SSI. These findings indicate that bacterial presence on the incision alone does not explain SSI development, implying that host factors, surgical technique, or systemic contamination (such as bacteraemia from the primary colic lesion) warrant investigation as critical contributors to post-operative infection; practitioners should recognise that intra-operative contamination may be less predictive of outcome than previously assumed, and that infection prevention strategies must address mechanisms beyond simple bacterial presence.
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Practical Takeaways
- •Presence of bacteria on laparotomy incisions during surgery does not reliably predict post-operative infection risk, suggesting other factors beyond peri-operative contamination drive SSI development
- •SSI causative organisms may originate from sources other than intra-operative wound contamination, warranting investigation of bacteraemia and systemic factors in SSI prevention strategies
- •Antimicrobial resistance (MRSA, ESBL-producers) detected on incisions does not necessarily correlate with clinical infection development in this cohort
Key Findings
- •7 of 31 horses (22.6%) developed surgical site infections following exploratory laparotomy
- •Bacterial culture prevalence increased progressively from pre- to post-operative periods, but positive intra-operative cultures did not predict SSI development
- •When SSI occurred, it was caused by different bacterial isolates than those cultured intra-operatively from the same incision
- •MRSA and ESBL-producing bacteria were identified post-operatively in 5 horses total, but none of these horses developed SSI