With increasing prevalence of antimicrobial resistant bacteria, it seems prudent to develop adjuvant antimicrobial approach for the treatment of burn wound infection.

A study published recently in Photodiagnosis and Photodynamic Therapy evaluated the effectiveness of antimicrobial photodynamic therapy (aPDT) using indocyanine green (ICG) in reducing the bacterial load and expression profiling of the quorum sensing (QS) system associated with the biofilm formation in multi-species bacterial biofilms.

Multi-species bacterial suspension including Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus was subjected to photosensitization with ICG, excited at a wavelength of 810 nm. The dose of ICG-aPDT contributing to the sub-significant reduction of colony forming unit (CFU)/mL was determined, followed by evaluation of gene expression levels of abaI, agrA, and lasI using real-time quantitative reverse transcription polymerase chain reaction. Investigators assessed lipid peroxidation, superoxide radicals and reactive oxygen species (ROS). The morphological changes of multi-species bacteria were also determined.

Maximal sub-significant reduction dose of aPDT against CFUs/mL of multi-species bacterial cells was noted with a combination of 31.2 μg/mL of ICG and irradiation by the diode laser for 1 min, with an estimated average output light energy of 31.2 J/cm2. There was a downregulation of expression levels of abaI, agrA, and lasI in A. baumannii, P. aeruginosa, and S. aureus to nearly 1.9-, 3.7-, and 4.9-fold, respectively. The amount of lipid peroxidation, superoxide radical production, and ROS generation was shown to increase significantly. Cell morphology revealed ICG-aPDT as a stressful condition for multi-species bacterial cells.

The study thus led to the conclusion that ICG-aPDT having antimicrobial, anti-biofilm, and gene expression inhibitor characteristics, besides ROS generation, can be a potential treatment for burn wound infections in vivo.

Source: Pourhajibagher M, Mahmoudi H, Rezaei-Soufi L, et al. Potentiation effects of antimicrobial photodynamic therapy on quorum sensing genes expression: A promising treatment for multi-species bacterial biofilms in burn wound infections. Photodiagnosis Photodyn Ther. 2020 Mar 9:101717.