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Home / Equine Research Bank / Equine Vet J / Effect of surgical antimicrobial prophylaxis duration for co...
Equine veterinary journal2025; 58(2); 390-403; doi: 10.1002/evj.70137

Effect of surgical antimicrobial prophylaxis duration for colic surgery on complications and resistome.

Abstract: Based on human studies, surgical antimicrobial (AMD) prophylaxis (SAP) beyond 24 h is unnecessary and potentially detrimental. Objective: To compare clinical and microbiological outcomes in patients receiving 24- or 72-h of SAP for colic surgery. Methods: Prospective randomised clinical trial. Methods: Horses that recovered from colic surgery were considered. Exclusion criteria were (1) age <2 years; (2) Miniature Horses, pony, and draught breeds; (3) azotaemia; (4) recent hospitalisation, colic surgery, or AMDs; (5) local AMD administration. Eligible horses were randomly assigned to receive SAP with potassium penicillin and gentamicin for 24- or 72-h. Clinical data and complications were compared between SAP groups. Admission and discharge faecal samples from a subset of horses (N = 49) underwent shotgun metagenomic sequencing on an Illumina platform. Host reads were filtered by aligning to reference genomes using the Burrows-Wheeler Aligner, and taxonomic classification was performed with kraken2. Sequencing reads were aligned to the Comprehensive Antimicrobial Resistance Database (CARD)5 and characterised using the AMR++ pipeline. The microbiome/resistome was characterised and compared between SAP groups over time. Results: One hundred and forty horses completed the study (24-h N = 71 and 72-h N = 69). The only clinical variable that was different between SAP groups was age (24-h median age 16 [IQR 9, 20] and 72-h 12 [6, 18] years, p = 0.03). There was no significant difference between groups for any complications including incisional infection (24-h 17 [95% CI 10-27]% and 72-h 16 [9-26]%, p = 0.9). Time was the main driver of changes in the microbiome/resistome: alpha diversity decreased while AMD resistance genes associated with administered AMD increased between admission and discharge. Discharge beta-lactam resistance genes were significantly higher in the 72-h than the 24-h group. Conclusions: Single hospital, small numbers for complications, clinicians not blinded to SAP group. Conclusions: SAP for 24-h is recommended for horses undergoing colic surgery.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-12-10 PubMed ID: 41369016PubMed Central: PMC12892381DOI: 10.1002/evj.70137Google Scholar: Lookup
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  • Journal Article
  • Randomized Controlled Trial
  • Veterinary

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated whether a shorter duration (24 hours) of surgical antimicrobial prophylaxis (SAP) is as effective as a longer duration (72 hours) in preventing complications after colic surgery in horses.
  • The research also examined how the duration of antibiotic use affects the horses’ gut microbiome and antimicrobial resistance genes (resistome).

Background

  • Surgical antimicrobial prophylaxis (SAP) involves giving antibiotics around the time of surgery to prevent infections.
  • Previous human studies suggest that giving antibiotics beyond 24 hours after surgery offers no added benefit and may even contribute to antimicrobial resistance.
  • There is limited data in veterinary medicine, especially for horses undergoing colic surgery, which is often a contaminated or clean-contaminated surgical procedure.

Study Design and Methods

  • Prospective randomized clinical trial conducted in horses recovering from colic surgery.
  • Inclusion and exclusion criteria applied to standardize the study group, excluding young horses, certain breeds, horses with kidney issues (azotemia), recent hospitalizations or antibiotic use, and local antibiotic administration.
  • Eligible horses were randomly assigned to receive SAP with potassium penicillin and gentamicin for either 24 hours or 72 hours.
  • Clinical data including post-surgical complications such as incisional infections were recorded and compared.
  • To assess the impact on the microbiome and resistome, faecal samples from a subset of 49 horses were collected at admission and discharge.
  • Shotgun metagenomic sequencing was performed on these samples using Illumina sequencing technology.
  • Bioinformatics analysis included:
    • Filtering host DNA using Burrows-Wheeler Aligner.
    • Taxonomic classification using kraken2.
    • Identifying antimicrobial resistance genes by aligning reads to the Comprehensive Antimicrobial Resistance Database (CARD) and analysis using the AMR++ pipeline.

Key Results

  • 140 horses completed the study: 71 in the 24-hour SAP group and 69 in the 72-hour SAP group.
  • Age was the only clinical variable that differed significantly, with the 24-hour group being slightly older on average.
  • No significant difference in complications, including incisional infection rates, was found between the two groups (approximately 16-17% infection rate in both groups).
  • The horses’ gut microbiome changed over time post-surgery, regardless of SAP duration:
    • Alpha diversity (a measure of species richness within each sample) decreased from admission to discharge, indicating reduced microbiome diversity post-surgery/antibiotic use.
    • The presence of antimicrobial resistance genes linked to the administered antibiotics increased from admission to discharge.
  • Horses receiving 72-hour SAP showed significantly higher levels of beta-lactam resistance genes at discharge compared to the 24-hour group, suggesting prolonged antibiotic use may enrich resistance genes.

Conclusions and Implications

  • Extending SAP from 24 to 72 hours after colic surgery in horses does not reduce surgical complications or infections.
  • Prolonged antibiotic use for 72 hours increases antimicrobial resistance genes in the gut microbiome, which has implications for antibiotic stewardship and resistance development.
  • The study supports recommendations for limiting SAP to 24 hours to minimize unnecessary antibiotic exposure while still protecting against postoperative infections.
  • Limitations include the study being conducted at a single hospital, modest sample size especially regarding the number of complication events, and that clinicians were not blinded to the SAP group assignments, which could introduce bias.
  • Overall, these findings contribute important evidence for veterinary surgical practices aiming to reduce antimicrobial resistance risks without compromising patient care.

Cite This Article

APA
Southwood LL, Long A, Perez J, Daniel S, Bittinger K, Aitken M, Redding L. (2025). Effect of surgical antimicrobial prophylaxis duration for colic surgery on complications and resistome. Equine Vet J, 58(2), 390-403. https://doi.org/10.1002/evj.70137

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 58
Issue: 2
Pages: 390-403

Researcher Affiliations

Southwood, Louise L
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett, Pennsylvania, USA.
Long, Alicia
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett, Pennsylvania, USA.
Perez, Jairo
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett, Pennsylvania, USA.
Daniel, Scott
  • Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Bittinger, Kyle
  • Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Aitken, Maia
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett, Pennsylvania, USA.
Redding, Laurel
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett, Pennsylvania, USA.

MeSH Terms

  • Horses
  • Animals
  • Horse Diseases / surgery
  • Horse Diseases / prevention & control
  • Horse Diseases / drug therapy
  • Horse Diseases / microbiology
  • Colic / veterinary
  • Colic / surgery
  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / therapeutic use
  • Antibiotic Prophylaxis / veterinary
  • Female
  • Male
  • Prospective Studies
  • Drug Resistance, Bacterial
  • Postoperative Complications / veterinary
  • Postoperative Complications / prevention & control

Grant Funding

  • Raymond Firestone Research Foundation

Conflict of Interest Statement

The authors declare no conflicts of interest.

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