Equine bone marrow-derived mesenchymal stromal cells reduce established S. aureus and E. coli biofilm matrix in vitro.
Authors: Khatibzadeh Sarah M, Dahlgren Linda A, Caswell Clayton C, Ducker William A, Werre Stephen R, Bogers Sophie H
Journal: PloS one
Summary
# Editorial Summary Established biofilms in equine orthopaedic infections present a significant clinical challenge, as their matrix structure shields bacteria from antibiotic penetration and immune defences, contributing to treatment failures and chronic disease. Researchers isolated mesenchymal stromal cells (MSC) from bone marrow of five Thoroughbreds and tested whether these cells could disrupt pre-formed biofilms of *Staphylococcus aureus* and *Escherichia coli* in vitro, either alone or combined with the aminoglycoside antibiotic amikacin, using a transwell co-culture system over 24–48 hours with measurements of biofilm area, biomass (crystal violet staining), and bacterial colony-forming units (CFU). MSC monotherapy significantly reduced *S. aureus* biofilm area and biomass at both timepoints and decreased *E. coli* biofilm area at 48 hours; when combined with amikacin, MSC enhanced reduction of *S. aureus* CFU at 48 hours and *E. coli* CFU at both timepoints compared to amikacin alone. The mechanism appeared to centre on matrix disruption rather than direct bacterial killing, though MSC performed differently depending on bacterial species—a distinction that may reflect differential interactions with Gram-positive versus Gram-negative cell walls. Whilst these in vitro results suggest potential clinical utility for MSC as an adjunctive therapy in biofilm-associated orthopaedic infections, further investigation of optimal MSC dosing, treatment timing, and biofilm–MSC interactions is essential before translating findings to in vivo equine models and clinical practice.
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Practical Takeaways
- •Equine bone marrow-derived MSC show promise for reducing established bacterial biofilms in orthopedic infections, particularly S. aureus, which could complement antibiotic therapy in difficult-to-treat infections
- •MSC combined with amikacin achieved superior biofilm reduction compared to either treatment alone, suggesting potential clinical synergy for combination therapies
- •Further in vivo studies are needed to determine optimal MSC dosing, treatment timing, and applicability to actual orthopedic infections before clinical adoption can be recommended
Key Findings
- •MSC significantly reduced S. aureus biofilms at both 24 and 48 hours and E. coli biofilm area at 48 hours compared to untreated controls
- •MSC combined with amikacin significantly reduced S. aureus biofilms versus amikacin alone and E. coli biofilms versus MSC alone at 48 hours
- •MSC significantly reduced S. aureus biomass at both timepoints and reduced S. aureus CFU at 48 hours versus untreated controls
- •MSC primarily disrupted biofilm matrix but demonstrated different efficacy against S. aureus versus E. coli