Antimicrobial photodynamic therapy\u2014a promising treatment for prosthetic joint infections

Timothy Briggs,Rita Ramalhete,David Mckenna,Simon Hislop,Melanie Coathup,Gordon Blunn,Caroline Bagley

doi:10.1007/s10103-017-2394-4

Timothy Briggs, Rita Ramalhete + Show 5 more

Open Access

https://doi.org/10.1007/s10103-017-2394-4

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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.

Highlights

The incidence of periprosthetic joint infection (PJI) is low, it results in substantial morbidity and is a considerable financial burden to the healthcare system
Results showed that in plates treated with methylene blue (MB) alone, all Staphylococci were eradicated (MSSA, methicillin-resistant Staphylococcus aureus (MRSA) and S. epidermidis), but the bactericidal effect was limited
The effect of Photodynamic Therapy (PDT) on P. aeruginosa was very limited with clusters of bacterial colonies still present at all MB concentrations (Fig. 4)

Summary

Introduction

The incidence of periprosthetic joint infection (PJI) is low, it results in substantial morbidity and is a considerable financial burden to the healthcare system. Whilst antibiotics are the traditional method used to treat implant infection, these have increasingly limited efficacy. In primary hip and knee replacement surgery, the rate for deep infection is reported to vary between 0.28 to 4% and 0.39 to 3.9%, respectively, with a higher incidence of infection seen in spinal implants [2,3,4,5]. In 2012, the National Joint Registry (NJR) for England and Wales reported a 12% revision rate in total hip replacement arthroplasty (THA) with 12% of those revised due to infection [6]. The lifetime risk of PJI from a haematogenous cause following Staphylococci bacteraemia is Lasers Med Sci (2018) 33:523–532

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