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Escherichia coli Sterilization Using a Light-Emitting Diode and Methylene Blue
Kouji Ogasawara1,2, Susumu Nakajima3, Hiroshi Sato1
1Sarufutsu Village National Health Insurance Hospital, Japan.
Background And Aims:
The prevalence of pathogenic Escherichia coli as well as E. coli O157 and antibiotic- resistant bacteria has increased. This study aimed to examine the effect of methylene blue (MB) with sodium bicarbonate (NaHCO3) against E. coli using photodynamic antimicrobial chemotherapy (PACT).
Materials And Methods:
MB was basified using NaHCO3. E. coli and basic MB were smeared on the culture media followed by irradiation using a red light-emitting diode (LED) at 660 nm. Energy densities of 5, 10, 15, and 20 J/cm2 were applied to the culture medium.After 24 h, the bactericidal effect of basic MB with LED irradiation was determined based on the bacterial growth.
Results:
The basic effect was observed with 1%-6% of NaHCO3 at 5 J/cm2.This effect increased between 1% and 2% of NaHCO3 at 10 J/cm2 and 15 J/cm2, whereas decreased at the NaHCO3 concentrations of > 2%. Moreover, this effect decreased at an energy density of 20 J/cm2. The biphasic basic effect on bactericidal activity was observed between pH 8.6-9.0.
Conclusions:
Thus, PACT using basic MB may be an effective method for pathogenic E. coli sterilization.
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