Staphyloxanthin Photolysis Potentiates Low Concentration Silver Nanoparticles in Eradication of Methicillin-resistant Staphylococcus aureus

The rise of antibiotic resistant bacteria, e.g., methicillin-resistant Staphylococcus aureus (MRSA), has resulted in a widespread search for alternative treatments not reliant on traditional antibiotics. Silver nanoparticles (AgNPs) have long been known to exhibit antimicrobial activity against a wide variety of bacterial species. However, the clinical application of AgNPs as an alternative to antibiotics has been limited by their toxicity at high concentrations. Here, via blue-light photolysis of staphyloxanthin (STX), a carotenoid pigment in the MRSA membrane, we are able to significantly increase the antimicrobial efficacy of AgNPs. With 4 h of 5 μg/mL AgNP exposure, there is no significant change in MRSA burden compared to the control. In contrast, a 99.99% reduction in MRSA burden is observed for samples exposed to 30 J/cm2 of pulsed blue light. The underlying mechanism is unveiled as that STX photolysis increases permeability of membrane and facilitates the uptake of AgNPs into the bacterium. This a...