Enhancement of photodynamic inactivation of Staphylococcus aureus biofilms by disruptive strategies

Photodynamic Therapy as a New Treatment for Chronic Rhinosinusitis - A Systematic Review

This review examines the latest evidence for photodynamic therapy (PDT) in treating chronic rhinosinusitis. MedLine, EMBASE and TRIP Database searches were conducted using the terms: "photodynamic" or "phototherapy" or "photo" and "sinusitis" or "rhinosinusitis," date range January 2000 to May 2020. A total of 192 records were initially identified, after duplicates and exclusions, 9 full papers and 3 abstracts were included. All study types including in-vitro, animal and human studies were evaluated. Whilst there is in-vitro evidence for the efficacy of PDT's bactericidal effect on drug resistant bacteria and biofilm viability, there are few clinical studies. PDT is a promising area of research, but larger, focused studies looking at the safety, delivery, efficacy, and patient selection are required before it can be considered a viable treatment for CRS.

An In Vitro Model to Study the Effect of 5-Aminolevulinic Acid-mediated Photodynamic Therapy on Staphylococcus aureus Biofilm

Staphylococcus aureus (S. aureus) is a common human pathogen, which causes pyogenic and systemic infections. S. aureus infections are difficult to eradicate not only due to the emergence of antibiotic-resistant strains but also its ability to form biofilms. Recently, photodynamic therapy (PDT) has been indicated as one of the potential treatments for controlling biofilm infections. However, further studies are required to improve our knowledge of its effect on bacterial biofilms, as well as the underlying mechanisms. This manuscript describes an in vitro model of PDT with 5-aminolevulinic acid (5-ALA), a precursor of the actual photosensitizer, protoporphyrin IX (PpIX). Briefly, mature S. aureus biofilms were incubated with ALA and then exposed to light. Subsequently, the antibacterial effect of ALA-PDT on S. aureus biofilm was quantified by calculating the colony forming units (CFUs) and visualized by viability fluorescent staining via confocal laser scanning microscopy (CLSM). Representative results demonstrated a strong antibacterial effect of ALA-PDT on S. aureus biofilms. This protocol is simple and can be used to develop an in vitro model to study the treatment of S. aureus biofilms with ALA-PDT. In the future, it could also be referenced in PDT studies utilizing other photosensitizers for different bacterial strains with minimal adjustments.