Abstract
Introduction: Cutibacterium acnes is gaining recognition as a leading pathogen after orthopaedic shoulder procedures. Photodynamic therapy, a combination of light and a photosensitizer, has demonstrated antimicrobial activity against C. acnes in the treatment of acne vulgaris. We sought to evaluate the effect of photodynamic therapy using blue light and photosensitizers on C. acnes isolates from shoulder prosthetic joint infections.Methods: C. acnes strains isolated from 19 patients with shoulder PJI were exposed to blue light alone (415 nm) or in combination with photosensitizers (fluorescein, riboflavin and demeclocycline). C. acnes strains were divided into 4 categories: Highly Sensitive (HS), Sensitive (S), Weakly Sensitive (WS), Resistant to blue light.Results: 13 of 19 C. acnes strains (68%) were S or HS to blue light alone. Of these 19 strains tested, 11 were tested with blue light and fluorescein or blue light plus riboflavin. Fluorescein (1 µg/mL) enhanced the effect of blue light in 6 of 11 strains (55%). Blue light plus riboflavin (10 µg/mL) resulted enhanced killing in 3 of 11 strains (27%), but produced a paradoxical photoprotective effect in 4 of 11 strains (36%), resulting in a net decrease compared to blue light alone. Demeclocycline, however, enhanced the effect of blue light in 16 of 17 strains (94 %).Conclusions: Blue light with the addition of photosensitizers killed C. acnes from periprosthetic shoulder infections in vitro, with demeclocycline having the most pronounced effect.
Highlights
Cutibacterium acnes is gaining recognition as a leading pathogen after orthopaedic shoulder procedures
Infection caused by C. acnes, formerly Propionibacterium acnes, presents unique diagnostic and therapeutic challenges to orthopaedic surgeons as the patient's clinical presentation is usually indolent and diagnostic markers may be within normal limits
We focused on blue rather than red light in this study.The importance of adjusting the culture turbidity in response to blue light is reflected by TW37 strain becoming much more resistant to blue light when suspended at a higher turbidity (OD600= 0.3) compared to the same strain at an Optical Density at 600 nm (OD600) of 0.1 (Fig 1C)
Summary
Cutibacterium acnes is gaining recognition as a leading pathogen after orthopaedic shoulder procedures. We sought to evaluate the effect of photodynamic therapy using blue light and photosensitizers on C. acnes isolates from shoulder prosthetic joint infections. Cutibacterium acnes (C. acnes) is recognized as one of the leading infecting pathogens after orthopaedic shoulder surgeries, especially arthroplasty procedures [1, 2]. More recently proposed infection prevention techniques include the use of preoperative topical benzoyl peroxide or topical clindamycin [8, 17,18,19]. Despite these efforts, C. acnes can persist and cause periprosthetic joint infections (PJI), which necessitates the development of novel infection prevention strategies [20]
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