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Developments in bacterial kill using blue light emitting diodes (LEDs)-

Violet Bumah

 Background and Objective The increasing burden of multiple drug resistant bacteria underscores the need to find innovative therapeutics for bacterial infection in clinical situations. Our team has shown that blue light is antimicrobial and has the potential to speed wound repair 1,2. To advance our line of work, we utilized a breakthrough technology, the CareWear wound patch, emitting blue 450 nm light, to treat P. acnes and MRSA in vitro. Methods Bacteria were grown in their respective media aerobicallyanaerobically at 37C until they reached logarithmic growth phase. Concentrations of 1x106 colony forming units (CFU) mL of Propionibacterium acnes (P. acnes) and methicillinresistant Staphylococcus aureus (MRSA) were plated and bacteria assigned to two groups; control and treated. Various irradiation protocols (average irradiance of 2, 3.5 and 4.5 mWcm2 in continuous wave mode and 2 or 3.5 mWcm2 in pulsed modes; and fluences ranging from 5  60 Jcm2) were applied after which plates were incubated at 37C, colonies photographed, counted and percent survival computed. Results CareWear450 nm light patches, effectively suppressed the growth of P. acnes and MRSA at low levels of optical irradiance and fluence when applied in specific pulsed modes and treatment sequences. Levels as low as 5 Jcm2 demonstrated 100% bacterial kill rates in vitro. This finding is a significant improvement over similar continuous wave blue light devices, which require energy levels greater than 60 Jcm2 to achieve comparable results. Moreover, it shows that, for maximum antimicrobial effect, it is not necessary to irradiate at the relatively high energy densities of 50  60 Jcm2 or higher as reported in our previous studies and those of others. Conclusion Blue light inactivates a host of bacteria, including the notoriously deadly MRSA and other drug-resistant bacteria. Our results show that bacterial clearance is achievable at much lower energy fluences using the new technology and protocol, which is not only more effective but naturally safer for patients and others.