With increased concern about overuse of antimicrobial drugs (AMDs), researchers are evaluating nontraditional therapies to treat many infectious conditions. Equine endometritis, which causes subfertility in mares, does not always respond successfully to AMDs. In a collaborative study, researchers in Brazil and at the University of Illinois College of Veterinary Medicine examined the in vitro antimicrobial activity of nontraditional therapies for treating endometritis.
Bacterial Equine Endometritis
Bacterial endometritis is often caused by Streptococcus zooepidemicus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus. Traditional treatment relies on uterine lavage, ecbolic drugs to induce uterine contractions, steroidal and non-steroidal anti-inflammatory medications, and uterine or systemic antibiotics. Not all mares respond to these traditional modalities.
Nontraditional Therapies for Equine Endometritis
When treating endometritis, it is important to break up the biofilm within the endometrial lining and to inhibit bacterial attachment and growth while also binding endo/exotoxins produced by pathogens. Nontraditional therapies used for these purposes include acetylcysteine, hydrogen peroxide, DMSO (dimethyl sulfoxide), and iodine solution. Veterinarians have also used chemical irritants such as kerosene and hypertonic dextrose. Hyperimmune or blood plasma, mycobacterium cell wall extract, stem cells, or platelet-rich plasma are other nontraditional options.
Microorganisms used in this in vitro study included the most common ones involved in chronic and difficult-to-treat endometritis: S. aureus, E. coli, P. aeruginosa, K. pneumoniae, and Candida albicans (fungal metritis). All these organisms are noteworthy for forming biofilms.
Experiment 1: Hydrogen Peroxide, LRS, Iodine, and DMSO
Experiment 1 subjected all five pathogens to hydrogen peroxide, Lactated Ringer’s solution (LRS), ozonated LRS, iodine, and DMSO. Results are as follows:
- Hydrogen peroxide at various concentrations showed 100% inhibition for all five organisms. The authors noted that 3% hydrogen peroxide is commonly used, but lower concentrations might be effective.
- DMSO elicited inhibition when administered at 20% concentration. The researchers warned, however, that endometrial tissue can ulcerate and become inflamed in response to this high concentration. This irritation usually resolves in three weeks.
- Iodine at a 4% solution diminished S. aureus and C. albicans by 60% and E. coli by 50% after 24 hours. Iodine at 10% concentration was bacteriostatic after three hours, but that strength can burn skin. Even a 1% iodine solution can cause chronic inflammatory responses in the endometrium. Iodine efficacy depends on concentration and contact time.
- Ozonated Lactated Ringer’s solution does not appear to harm endometrial tissue, but it had no inhibitory effect in this study. It is not able to disrupt biofilm.
Experiment 2: PRP and PPP
In Experiment 2, researchers evaluated the alleged antimicrobial properties of platelet-rich plasma (PRP) and platelet-poor plasma (PPP). They found that PRP performed better than PPP. PRP interaction with leukocytes augments its bacteriostatic ability. Maximum inhibitory effects occur within the first two hours, likely necessitating multiple treatment applications.
Final Thoughts
Based on these findings, the authors suggest that hydrogen peroxide and PRP have the greatest antimicrobial effect on endometrial pathogens in vitro. More studies are necessary to determine the highest concentrations necessary to achieve this effect.
Reference
Mazzuchini MP, Lisboa FP, de Castro JI, et al. In vitro antimicrobial activity of non-traditional therapies for infectious endometritis in mares. Equine Veterinary Journal Sept 2024; DOI: 10.1111/evj.14423
Related Reading
- Responsible Antimicrobial Usage in Horses
- Disease Du Jour: Uterine Biofilms in Mares
- Clearing Uterine Fluid From Mares After Mating
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