Characterization of surface properties and antimicrobial activity of autochthonous lactic acid bacteria isolated from the reproductive tract of healthy mares.

Overview

• This study investigated beneficial lactic acid bacteria (LAB) naturally present in the reproductive tract of healthy mares.
• Researchers characterized these bacteria’s surface properties and tested their ability to inhibit pathogens causing equine endometritis, suggesting potential for probiotic treatments to prevent this disease.

Background and Motivation

• Equine endometritis is a common cause of reduced fertility in mares, posing economic challenges in horse breeding.
• Traditional antimicrobial treatments are becoming less effective due to rising antibiotic resistance.
• Using beneficial bacteria (probiotics) offers a non-antibiotic “One Health” approach to preventing infections.
• Little detailed research existed on autochthonous (naturally occurring) vaginal LAB in horses prior to this study.

Sample Collection and Isolate Identification

• Samples were taken from the vaginal tracts of 15 healthy thoroughbred mares.
• 25 presumptive LAB isolates were initially obtained; 24 were confirmed as LAB.
• The 17 most promising isolates were further identified using MALDI-TOF mass spectrometry.
• Species identified include:
  • Pediococcus pentosaceus (6 isolates)
  • Enterococcus hirae (6 isolates)
  • Enterococcus faecalis (4 isolates)
  • Weissella cibaria (1 isolate)

Characterization of Surface Properties

• Various surface characteristics related to probiotic potential were measured:
  • Autoaggregation: All isolates demonstrated the ability to clump together, a desirable probiotic trait.
  • Adhesion to equine epithelial cells: Most isolates showed medium to high adhesion, indicating potential to colonize the vaginal mucosa.
  • Hydrophobicity: Generally low, affecting interaction with host cells and surfaces.
  • Biofilm formation: All isolates formed biofilms in different media; biofilm formation was better without surfactants, important for persistence.
  • Exopolysaccharide (EPS) production: 54% of isolates produced EPS, with production influenced by carbohydrate sources, which can protect bacteria and aid adhesion.

Antimicrobial Activity

• The isolates were tested against 17 different bacteria species commonly implicated in equine endometritis.
• Approximately 71% of the LAB isolates inhibited the growth of all target pathogens.
• Notably strong inhibition: Against Streptococcus zooepidemicus, a major cause of equine endometritis.

Compatibility and Probiotic Formulation Potential

• Compatibility assays showed some isolates could coexist without adverse interactions.
• This suggests feasibility of creating a multi-strain probiotic formulation that harnesses combined beneficial properties.
• Multi-strain probiotics may offer enhanced protection through diverse mechanisms.

Conclusions and Future Directions

• This research is among the first to thoroughly evaluate vaginal LAB as potential probiotics against equine reproductive tract infections.
• Results support exploring multi-strain probiotic formulations to prevent equine endometritis as a promising alternative to antibiotics.
• Additional studies are necessary to:
  • Assess technological aspects such as formulation and storage stability.
  • Confirm safety profiles of candidate strains for use in animals.
  • Test probiotic efficacy and behavior in vivo within mares.