Equine bone marrow-derived mesenchymal stromal cells reduce established S. aureus and E. coli biofilm matrix in vitro.

This research study explores the use of equine bone marrow-derived mesenchymal stromal cells (MSC) in reducing bacterial biofilms of S. aureus and E. coli. It indicates that these MSCs, particularly when paired with the antibiotic amikacin sulfate, were successful in diminishing established biofilms and their matrices significantly.

Research Methodology and Aim

• The research aimed to evaluate the potency of MSCs in reducing established biofilms of S. aureus or E. coli – both of which pose severe risks to humans and horses in cases of orthopedic infections.
• The researchers hypothesized that MSCs could lessen biofilm matrix and the output of colony-forming units (CFU), which are measures of viable bacterial cells. They anticipated that a combination of MSCs and the antibiotic amikacin sulfate would have a more profound reduction effect than either treatment alone.
• The MSCs used in this study were isolated from adults Thoroughbred horses in an antibiotic-free environment.

Experiment Procedure

• The research team generated 24-hour S. aureus or E. coli biofilms and co-cultured them in triplicate for durations of 24 or 48 hours using a transwell plate system. The various treatments included non-treatment (acting as the negative control), treatment with 30 μg/mL of amikacin, 1 x 106 passage 3 MSC and a combination of MSC with 30 μg/mL of amikacin.
• Subsequently, the treated biofilms were photographed and the biofilm area was digitally quantified. The biomass was determined via crystal violet staining, and CFUs were quantified post enzymatic digestion.
• Analyzing the data followed the use of mixed model ANOVA with Tukey post-hoc comparisons. A p-value of less than 0.05 was considered statistically significant.

Results and Conclusion

• MSCs significantly reduced the S. aureus biofilms at all measured time points and the E. coli biofilm area at 48 hours when compared to untreated controls.
• MSCs combined with amikacin achieved a more significant reduction of S. aureus biofilms in comparison to treatment with just amikacin and E. coli biofilms as compared to just MSC at 48 hours.
• MSCs also significantly reduced the biomass and CFU of S. aureus at certain time points versus the untreated controls. The combination of MSC and amikacin also achieved a more significant reduction in these metrics as compared to standalone treatments.
• However, the effect of MSC on S. aureus and E. coli was different, indicating a need for further study for understanding the interactions between MSC and the biofilm.
• The study recommends further review on biofilm-MSC interactions, MSC dose, and treatment time before testing in vivo.