Azure A as a promising candidate for antimicrobial photodynamic therapy of acne-related bacteria.

Antimicrobial photodynamic inactivation (aPDT) is an effective technique for treating acne vulgaris, due to its efficiency in inactivating multiresistant bacteria and the absence of systemic side effects. This study investigated the potential of the dye Azure A (AZA), belonging to the phenothiazine class, as a photosensitizer (PS) in aPDT to combat the gram-positive bacteria Staphylococcus epidermidis and Cutibacterium acnes, both associated with inflammatory acne vulgaris. The efficiency of AZA was compared to Orthotoluidine Blue (OTB), evaluating the absorbance spectra, singlet oxygen generation rate, and minimum bactericidal concentration (MBC) at different optical fluence values and concentrations. The results demonstrated that AZA and OTB have similar spectroscopic characteristics and single oxygen generation rates, and they could inactivate both bacteria at an MBC of 0.78 [Formula: see text] for the smallest tested optical fluence. These findings indicate that AZA is an excellent candidate for topical aPDT applications in treating acne vulgaris and other associated infections by such bacteria.