Photoinactivation of Bacteria Attached to Glass and Acrylic Surfaces by 405 nm Light: Potential Application for Biofilm Decontamination

Attachment of bacteria to surfaces and subsequent biofilm formation remains a major cause of cross-contamination capable of inducing both food-related illness and nosocomial infections. Resistance to many current disinfection technologies means facilitating their removal is often difficult. The aim of this study was to investigate the efficacy of 405nm light for inactivation of bacterial attached as biofilms to glass and acrylic. Escherichia coli biofilms (10(3)-10(8)CFUmL(-1)) were generated on glass and acrylic surfaces and exposed for increasing times to 405nm light (5-60min) at ca 140mWcm(-2). Successful inactivation of biofilms has been demonstrated, with results highlighting complete/near-complete inactivation (up to 5 log(10) reduction on acrylic and 7 log(10) on glass). Results also highlight that inactivation of bacterial biofilms could be achieved whether the biofilm was on the upper directly exposed surface or indirectly exposed underside surface. Statistically significant inactivation was also shown with a range of other microorganisms associated with biofilm formation (Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes). Results from this study have demonstrated significant inactivation of bacteria ranging from monolayers to densely populated biofilms using 405nm light, highlighting that with further development this technology may have potential applications for biofilm decontamination in food and clinical settings.