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Phage Therapy for a Refractory and Multidrug-resistant Equine Surgical Site Infection.
Abstract: A 14-year-old American Quarter Horse mare developed a refractory deep surgical site infection following emergency celiotomy for acute right dorsal large colon displacement with 180° volvulus. Initial cultures revealed a high-burden polymicrobial infection with and , associated with delayed healing, and later followed by multidrug-resistant , further limiting therapeutic options. Phage therapy was initiated using a customized lytic phage cocktail administered topically on a daily basis over a 35-day period, with cocktail composition guided by daily wound culture results. Phage therapy markedly reduced colony-forming units of targeted pathogens and promoted progressive healing. Wound microbial communities varied during treatment, demonstrating selective pathogen control while preventing residual populations from recolonizing the tissue. By the time of hospital discharge, the wound surface area had decreased by more than 85%, and the body wall had healed without evidence of acute herniation. This case highlights the feasibility, safety, and clinical potential of adaptive phage therapy for managing refractory multidrug-resistant equine wound infections.
Copyright: © 2026 International Journal of Veterinary Science and Medicine.
Publication Date: 2026-06-18 PubMed ID: 42434394PubMed Central: PMC13354132DOI: 10.4103/IJVSM.IJVSM_19_26Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
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Summary
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Phage therapy was used to successfully treat a difficult and drug-resistant surgical wound infection in a horse, resulting in significant healing and reduction of harmful bacteria.
Background and Case Description
- A 14-year-old American Quarter Horse mare experienced a deep surgical site infection after emergency surgery for a twisted large colon (180° volvulus).
- The infection was initially polymicrobial, involving multiple types of bacteria causing delayed wound healing.
- Later, a multidrug-resistant bacterium developed, complicating treatment because of limited antibiotic options.
Phage Therapy Approach
- Researchers used a customized phage cocktail—viruses that specifically infect and kill bacteria—to treat the infection.
- The cocktail was lytic, meaning the phages destroy their bacterial hosts upon infection.
- Phage therapy was administered topically to the wound daily for 35 days.
- The composition of the phage cocktail was adapted daily based on the results of wound culture tests, allowing targeted treatment of the current bacterial populations.
Outcomes and Microbial Dynamics
- Phage therapy significantly reduced bacterial colony-forming units of the targeted drug-resistant pathogens.
- This selective targeting controlled harmful bacteria while preventing other bacterial communities from recolonizing the wound surface.
- Wound healing progressed steadily, with more than an 85% reduction in wound surface area by hospital discharge.
- The body wall healed properly with no signs of complications such as herniation.
Clinical Significance
- This study demonstrates the practical feasibility and safety of using adaptive phage therapy to manage difficult, multidrug-resistant wound infections in horses.
- The success highlights the potential for phage therapy as an alternative or adjunct treatment option when conventional antibiotics fail due to resistance.
- Adaptive selection of phage cocktails guided by ongoing microbial culture data is a promising strategy to maintain effective bacterial control over time.
- The approach may have broader implications for veterinary and possibly human medicine, especially in dealing with refractory infections caused by resistant pathogens.
Cite This Article
APA
Alverson D, Gustafson G, Duesterdiec-Zelmer KF, Kamm JL, Danelishvili L.
(2026).
Phage Therapy for a Refractory and Multidrug-resistant Equine Surgical Site Infection.
Int J Vet Sci Med, 14, 9.
https://doi.org/10.4103/IJVSM.IJVSM_19_26 Publication
Researcher Affiliations
- Department of Biomedical Sciences, Gary R. Carlson, MD, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
- Department of Clinical Sciences, Gary R. Carlson, MD, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
- Department of Clinical Sciences, Gary R. Carlson, MD, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
- Department of Clinical Sciences, Gary R. Carlson, MD, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
- Department of Biomedical Sciences, Gary R. Carlson, MD, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
Conflict of Interest Statement
There are no conflicts of interest.
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