Effects of Photodynamic Inactivation on Susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) in Mixed Culture

Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) are bacteria of extreme concern to public health, as they are intrinsically related to hospital infections and difficulty in treating them. Bacteria have a pattern of behavior observed in survival curves. Mixed cultures behave differently from pure cultures and when subjected to photodynamic inactivation (PDI) treatment there are effects resulting in pathogenic and resistant bacteria becoming more susceptible. Photodynamic inactivation treatment was carried out using a stock solution (5 mM) of curcumin as a photosensitizer, irradiation with an LED lighting device (Biotable - produced by MM Optics-Brasil) emitting a wavelength of 450 nm and varying light doses between 1 J/cm², 2 J/cm² and 5 J/cm². By adding competing bacteria such as Staphylococcus epidermidis , it is possible to observe promising patterns for the treatment of resistant bacterial infections with PDI, such as a bacterial reduction of 3 log.