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Antimicrobial photodynamic therapy-a promising treatment for prosthetic joint infections
Timothy Briggs1, Gordon Blunn2, Simon Hislop1
1Royal National Orthopaedic Hospital, HA7 4LP, Brockley Hill, HA7 4LP, Stanmore, UK.
Abstract:
Periprosthetic joint infection (PJI) is associated with high patient morbidity and a large financial cost. This study investigated Photodynamic Therapy (PDT) as a means of eradicating bacteria that cause PJI, using a laser with a 665-nm wavelength and methylene blue (MB) as the photosensitizer. The effectiveness of MB concentration on the growth inhibition of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa and Acinetobacter baumannii was investigated. The effect of laser dose was also investigated and the optimized PDT method was used to investigate its bactericidal effect on species within planktonic culture and following the formation of a biofilm on polished titanium and hydroxyapatite coated titanium discs. Results showed that Staphylococci were eradicated at the lowest concentration of 0.1 mM methylene blue (MB). With P. aeruginosa and A. baumannii, increasing the MB concentration improved the bactericidal effect. When the laser dose was increased, results showed that the higher the power of the laser the more bacteria were eradicated with a laser power ≥ 35 J/cm2 and an irradiance of 35 mW/cm2, eradicating all S. epidermidis. The optimized PDT method had a significant bactericidal effect against planktonic MRSA and S. epidermidis compared to MB alone, laser alone, or control (no treatment). When biofilms were formed, PDT treatment had a significantly higher bactericidal effect than MB alone and laser alone for all species of bacteria investigated on the polished disc surfaces. P. aeruginosa grown in a biofilm was shown to be less sensitive to PDT when compared to Staphylococci, and a HA-coated surface reduced the effectiveness of PDT. This study demonstrated that PDT is effective for killing bacteria that cause PJI.
Insights
Photodynamic therapy (PDT) effectively eradicates bacteria causing periprosthetic joint infection (PJI). This laser and methylene blue treatment shows significant bactericidal effects against planktonic and biofilm bacteria, offering a promising PJI treatment.
Area of Science:
- Biomedical Engineering
- Photomedicine
- Infectious Diseases
Background:
- Periprosthetic joint infection (PJI) presents significant patient morbidity and economic burden.
- Current treatments for PJI have limitations, necessitating novel therapeutic approaches.
- Photodynamic therapy (PDT) is explored as a potential antimicrobial strategy.
Purpose of the Study:
- To investigate the efficacy of Photodynamic Therapy (PDT) in eradicating bacteria responsible for PJI.
- To determine the optimal parameters for PDT, including methylene blue (MB) concentration and laser dose.
- To evaluate PDT's effectiveness against planktonic bacteria and biofilms on implant materials.
Main Methods:
- Utilized a 665-nm wavelength laser and methylene blue (MB) as the photosensitizer.
- Assessed MB concentration effects on methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa, and Acinetobacter baumannii.
- Investigated laser dose parameters (power, irradiance) and evaluated PDT against planktonic cultures and biofilms on titanium and hydroxyapatite-coated titanium discs.
Main Results:
- Staphylococci were eradicated at low MB concentrations (0.1 mM).
- Increasing MB concentration enhanced bactericidal effects for P. aeruginosa and A. baumannii.
- Optimized PDT demonstrated significant bactericidal activity against planktonic MRSA and S. epidermidis.
- PDT showed superior efficacy against biofilms on polished titanium compared to MB or laser alone.
- Biofilm P. aeruginosa exhibited reduced sensitivity, and hydroxyapatite coatings diminished PDT effectiveness.
Conclusions:
- Photodynamic therapy (PDT) is a viable method for eradicating bacteria implicated in PJI.
- Optimized PDT parameters demonstrate potent antimicrobial activity against key PJI pathogens.
- PDT offers a promising adjunctive or alternative treatment modality for PJI, particularly on metallic implant surfaces.
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