Abstract:

Objective To investigate the effects of 460 nm visible light (blue light) on planktonic and biofilm Escherichia coli (E.coli). Methods E.coli samples were isolated from wards of the Department of Burn and identified by the microbial identification system. The planktonic E.coli were irradiated by 460 nm visible light of different energy and the anti-bacteria effects of 460 nm visible light were evaluated by the colony counting and LIVE/DEAD staining. The E.coli biofilm model was built and irradiated by 460nm visible light of 240 J/cm² and 360 J/cm² after being identified by FM 1.43 and crystal violet staining. The survival of E.coli in the biofilm was observed by the LIVE/DEAD staining and laser confocal microscope and compared to samples without being irradiated by the light. Results Compared to the control group, the number of colonies of E.coli samples decreased significantly after being irradiated by 460 nm visible light of 60 J/cm² and above and showed dose effect relation. The death rate of E.coli in the biofilm was significantly higher than that of E.coli of the control group after being irradiated by 460 nm visible light of 240 J/cm² and 360 J/cm². Conclusion Visible light of 460 nm can effectively inhibit planktonic and biofilm E.coli.

Key words: 460 nm visible light (blue light), biofilm, Escherichia coli, antibacterial effect