Abstract
BackgroundIn a recent study we showed that blue light inactivates methicillin-resistant Staphylococcus aureus (MRSA) by perturbing, depolarizing, and disrupting its cell membrane. PurposeThe current study presents visual evidence that the observed biochemical changes also result in cell metabolic changes and structural alteration of the cell membrane. MethodsCultures of MRSA were treated with 450 nm pulsed blue light (PBL) at 3 mW/cm2 irradiance, using a sub lethal dose of 2.7 J/cm2 radiant exposure three times at 30-min intervals. Following 24 h incubation at 37 °C, irradiated colonies and control non-irradiated colonies were processed for light and transmission electron microscopy. ResultsThe images obtained revealed three major effects of PBL; (1) disruption of MRSA cell membrane, (2) alteration of membrane structure, and (3) disruption of cell replication. ConclusionThese signs of bacterial inactivation at a dose deliberately selected to be sub-lethal supports our previous finding that rapid depolarization of bacterial cell membrane and disruption of cellular function comprise another mechanism underlying photo-inactivation of bacteria. Further, it affirms the potency of PBL.
Published Version
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