Equine uterine sanitizer: in vitro inhibition of endometritis-causing microorganisms and its stability to dilute antibiotics.

Overview

• This research investigates a commercially available uterine sanitizer’s ability to inhibit microorganisms that cause endometritis in mares and examines its stability when mixed with common antibiotics in laboratory conditions.

Background

• Endometritis is a major cause of reduced fertility in mares.
• While many mares respond to standard treatments, some require alternative therapies if the usual treatments fail.
• A commercially available product labeled as a uterine sanitizer has not previously been evaluated for its antimicrobial properties or compatibility with antibiotics.

Aims of the Study

• To determine the in vitro antimicrobial effects of the uterine sanitizer on microorganisms frequently associated with endometritis.
• To assess the chemical and physical stability of commonly used antibiotics when diluted with the uterine sanitizer at various temperatures.

Methods – Experiment 1: Antimicrobial Testing

• Microorganisms tested included Escherichia species, Staphylococcus species, Klebsiella species, Pseudomonas species, and Candida species.
• The microdilution broth technique was used to culture microorganisms in the presence of different concentrations of the uterine sanitizer.
• Percentage inhibition of microbial growth was calculated using optical density measurements.
• Minimum inhibitory concentrations (MIC) were determined:
  • MIC 100%: concentration that completely inhibited growth, determined with resazurin dye technique.
  • MIC 50% and MIC 90%: concentrations inhibiting 50% and 90% of growth, respectively, determined via dose-response nonlinear regression.

Methods – Experiment 2: Stability Testing of Antibiotic Dilutions

• The uterine sanitizer was used as a diluent for commonly used antibiotics, bringing the final volume to 90 mL.
• Samples were stored at three temperatures to mimic different clinical or storage conditions: 5°C (refrigeration), 21°C (room temperature), and 37°C (body temperature).
• pH measurements were recorded immediately (0 h) and at 1, 3, 6, and 24 hours after antibiotic dilution to monitor potential chemical changes.
• Visual observations looked for precipitation or other signs of incompatibility.

Results – Antimicrobial Efficacy

• The uterine sanitizer showed antimicrobial activity against all tested microorganisms.
• Escherichia species were the most susceptible to the sanitizer.
• Pseudomonas species exhibited the highest resistance.
• The product’s pH measured around 4, indicating acidic properties that may contribute to antimicrobial action.

Results – Stability of Antibiotic Dilutions

• When antibiotics were diluted with the uterine sanitizer, their pH remained stable across all tested temperatures and time points.
• No precipitation or visible incompatibility was observed during the 24-hour testing period.
• This suggests that the uterine sanitizer does not chemically or physically interfere with the antibiotics tested.

Conclusions and Implications

• The uterine sanitizer has demonstrated in vitro antimicrobial effects against key microorganisms involved in equine endometritis.
• The product remains stable and compatible when used as a diluent for antibiotics, which may enhance combined antimicrobial efficacy.
• These findings support the potential use of the uterine sanitizer as an adjunct or alternative in treating endometritis, particularly in mares unresponsive to conventional therapies.
• However, safety and effectiveness in live animals (in vivo) need to be thoroughly evaluated before clinical application.