Antimicrobial photodynamic therapy (aPDT) for treating methicillin-resistant Staphylococcus aureus (MRSA) infections has gained increasing attention in recent years. This study aimed to evaluate the potential of quercetin as a photosensitizer for aPDT. In vitro assays were conducted to assess the cytotoxicity and the antibacterial activity of quercetin photoactivated with blue LED light. In in vivo assays, and intradermal infection model was conducted in mice to evaluate the quercetin antimicrobial activity and cytokine production. The in vitro experiments showed low compound toxicity and antimicrobial activity accompanied by the generation of singlet oxygen. BALB/c mice infected with MRSA and treated with quercetin exhibited a reduced bacterial load in the draining lymph nodes and decreased recruitment of polymorphonuclear cells at the infection site. In response to infection, a strong interaction between the cytokines IL-12 and TNF-α was observed in the groups treated with quercetin. These observations support quercetin's anti-inflammatory and antimicrobial potential in infections with resistant strains of MRSA.
Galantini et al. (Tue,) studied this question.