THESIS
2018
xviii, 195 pages : illustrations ; 30 cm
Abstract
Each year, hospital acquired infections (HAIs) take countless lives worldwide. Of all
these infections, a large proportion can be attributed to multi drug resistant organisms
(MDROs). MDROs can be resistant to one or more classes of antibiotics and have
evolved as a response to the abuse of antibiotics. At present there are more than 15
classes of antibiotics, for all of which resistance mechanisms evolved. Multi-drug
resistant S.aureus, vancomycin resistant enterococcus, carbapenem resistant
Escherichia coli, multi drug resistant Pseudomonas aeruginosa, are the most common
and harmful MDROs, requiring strict control. The survivability of MDROs on
surfaces is long and cross contamination plays an important role in the transmission of
these pathogens.
Although there are many gu...[
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Each year, hospital acquired infections (HAIs) take countless lives worldwide. Of all
these infections, a large proportion can be attributed to multi drug resistant organisms
(MDROs). MDROs can be resistant to one or more classes of antibiotics and have
evolved as a response to the abuse of antibiotics. At present there are more than 15
classes of antibiotics, for all of which resistance mechanisms evolved. Multi-drug
resistant S.aureus, vancomycin resistant enterococcus, carbapenem resistant
Escherichia coli, multi drug resistant Pseudomonas aeruginosa, are the most common
and harmful MDROs, requiring strict control. The survivability of MDROs on
surfaces is long and cross contamination plays an important role in the transmission of
these pathogens.
Although there are many guidelines regarding the cleaning and disinfection of the
exposed surfaces of medical equipment, infections still break out at times. To
confront the high morbidity and mortality of these infections, many methods of
disinfection are under development. The most popular method used in local
healthcare setting is 1:49 bleach. However disinfection technologies using light,
which leaves no residual chemicals, are also used.
Blue LEDs emitting continuous light at wavelengths of 405nm and 470nm exhibit
desirable bactericidal activity against S.aureus, P.aeruginosa, MRSA and MRPA, but
the bactericidal efficiency in substantially increased using pulsed blue LEDs with
same exposure dosage. Pulsed UVC provides remarkable bactericidal effects at lower
dosages and energy consumption. A light disinfection device combining the three
wavelengths of light was assembled and evaluated. The resulting light disinfection
device showed outstanding disinfection effects against MDROs on different surfaces
including plastic, glass, agar, liquids and porous material.
The bactericidal mechanisms of 405nm, 470nm blue LED and light disinfection
device all result from reactive oxygen species (ROS) created during exposure, but the
specific action modes are different, as the oxidation effects of ROS are non-specific.
Exposure to 405nm blue LEDs affects the bacterial plasma membrane resulting in bacterial death, while exposure to 470nm blue LEDs is genotoxic. The light
disinfection device used not only these two disinfection modes but also increases the
membrane deconstruction effect and genotoxicity of each wavelength of light.
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