Phage-­ loaded biomimetic apatite powder and biofilms

Bacterial biofilms represent a major challenge in the treatment of chronic infections due to their high tolerance to conventional antibiotics, notably seen in bone and joint infections. Bacteriophage therapy has re-emerged as a promising alternative or complementary strategy to address these limitations. In our lab, we investigate the use of bacteriophages encapsulated within a calcium phosphate-based delivery system known as biomimetic apatite powder, designed to mimic the mineral phase of bone tissue and ensure localized antimicrobial activity.

Phages specifically targeting Staphylococcus aureus and Escherichia coli were incorporated into this biomimetic apatite material using a precipitation process that preserves phage viability. The antibacterial efficacy of this system was evaluated against both planctonic infection and mature biofilms formed by abovementioned bacteriae. Our results demonstrate that phage-loaded biomimetic apatite significantly reduces viable bacterial counts and biofilm activity, highlighting the capacity of this encapsulation system to deliver active phages in a sustained and localized manner. Planctonic culture of E. coli and S. aureus were completely eradicated (0 CFU, 7 log reduction) after 2 hours of incubation with the phage loaded material. Biofilm culture of S.aureus were almost completely eradicated ( ∼6,4 CFU, 5 log reduction) after 5 days of incubation with the lyophiliosed phage-loaded material but not with the lyophilised version (∼2,8.10³ CFU, 3 log reduction).

Furthermore, we explored the synergistic effects between phage therapy and conventional antibiotics. Combined treatments resulted in enhanced biofilm disruption and bacterial eradication compared to phages or antibiotics alone, suggesting a strong synergistic interaction. This combined approach may help overcome antibiotic tolerance associated with biofilms while reducing the required antibiotic doses as shown in other studies.

Overall, our findings support the potential of biomimetic apatite powders as an effective delivery platform for bacteriophages and as a promising strategy for the treatment of biofilm-associated infections, particularly in the context of bone and joint diseases.