Evaluation of visible light and natural photosensitizers against and planktonic cells and biofilm.

Antimicrobial photoinactivation (API) has shown some promise in potentially treating different nosocomial bacterial infections, however, its application on staphylococci, especially other than or methicillin-resistant (MRSA) species is still limited. Although is a well-known and important nosocomial pathogen, several other species of the genus, particularly coagulase-negative (CNS) species such as and , can also cause healthcare-associated infections and foodborne intoxications. CNS are often involved in resilient biofilm formation on medical devices and can cause infections in patients with compromised immune systems or those undergoing invasive procedures. In this study, the effects of chlorophyllin and riboflavin-mediated API on and planktonic cells and biofilm are demonstrated for the first time. Based on the residual growth determination and metabolic reduction ability changes, higher inactivating efficiency of chlorophyllin-mediated API was determined against the planktonic cells of both tested species of bacteria and against biofilm. Some insights on whether aqueous solutions of riboflavin and chlorophyllin, when illuminated with optimal exciting wavelength (440 nm and 402 nm, respectively) generate O, are also provided in this work.