Assessment of fecal bacterial viability and diversity in fresh and frozen fecal microbiota transplant (FMT) product in horses.
Authors: Long Alicia E, Pitta Dipti, Hennessy Meagan, Indugu Nagaraju, Vecchiarelli Bonnie, Luethy Daniela, Aceto Helen, Hurcombe Samuel
Journal: BMC veterinary research
Summary
# Editorial Summary Faecal microbiota transplantation (FMT) is increasingly used in equine practice to restore healthy gut microbial populations, yet the field lacks standardised protocols and basic data on whether the bacteria being transplanted are actually alive and metabolically active. Long and colleagues addressed this knowledge gap by comparing total bacterial DNA (dead and living combined) against viable, metabolically active bacteria in equine FMT products stored under various conditions—including two freezing temperatures (-20°C and -80°C), two preservation buffers (saline with or without glycerol), and four timepoints over 90 days. Using 16S rRNA gene sequencing of DNA and RNA extracts from faeces of three healthy donor horses, the team could distinguish between the complete microbial population and the fraction capable of metabolic activity. The findings reveal critical differences in bacterial viability depending on storage method, with direct implications for how practitioners prepare, store, and administer FMT—particularly regarding whether frozen FMT products retain sufficient viable bacteria to achieve therapeutic efficacy, and which preservation and temperature protocols best maintain bacterial integrity. These data provide the first standardisation benchmarks for equine FMT, enabling practitioners to optimise their protocols based on evidence rather than empirical practice.
Read the full abstract on PubMed
Practical Takeaways
- •If using FMT in your practice, ultra-low temperature freezing (-80°C) is preferable to standard freezer storage (-20°C) for maintaining viable bacterial populations
- •Fresh FMT product will contain the highest proportion of metabolically active bacteria, but frozen product can be effective if stored properly at -80°C
- •Standardization of FMT preparation and storage protocols is urgently needed in equine practice to ensure consistent therapeutic efficacy
Key Findings
- •Fresh fecal samples showed higher metabolically active bacterial populations compared to frozen samples across all storage conditions
- •Freezing at -80°C preserved bacterial viability better than -20°C storage over 90 days
- •Addition of glycerol as cryoprotectant did not significantly improve bacterial viability compared to saline alone
- •Bacterial diversity (richness and evenness) remained relatively stable across storage conditions despite changes in viability