The efficacy of vacuum-ultraviolet light disinfection of some common environmental pathogens

Abstract

Background: This study is to elucidate the disinfection effect of ozone producing low-pressure Hg vapor lamps against human pathogens. Ozone producing low-pressure Hg vapor lamps emit mainly 254 nm ultraviolet light C (UVC) with about 10% power of Vacuum-ultraviolet (VUV) light at 185 nm. The combination of UVC and VUV can inactivate airborne pathogens by disrupting the genetic materials or generation of reactive oxygen species, respectively. In this study, inactivation of common bacteria including Escherichia coli ATCC25922 (E. coli), Extended Spectrum Beta-Lactamaseproducing E. coli (ESBL), Methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis (MTB), and that of influenza A viruses H1N1 and H3N2 under the radiation from ozone producing low-pressure Hg vapor lamps was examined. Log reduction values at different treatment durations were determined. Methods: In vitro tests were carried out. Various bacterium and virus suspensions were added onto nitrocellulose filter papers and subjected to the illumination from ozone producing low-pressure Hg vapor lamps. The extents of pathogen inactivation at different illumination times were investigated by conducting a series of experiments with increasing duration of illumination. log10 reduction in CFU/ml and reduction at log10(TCID 50 ) were respectively measured for bacteria and viruses. The disinfection effectiveness of this type of lamps against the pathogens under the environment with a moderate barrier to light was therefore evaluated. Results: Ozone producing low-pressure Hg vapor lamp successfully inactivated these human pathogens. Nevertheless, among these pathogens, disinfection of MTB required more intense treatment. In the best tested situation, 3-log10 inactivation of pathogens can be achieved with ≤10 min of VUV treatment except MTB which needed about 20 min. This demonstrated the high resistance against UV disinfection of MTB.Conclusions: Following the criteria that valid germicidal results can be reflected with 3-log10 inactivation for bacteria, 4-log10 inactivation for viruses and 5-log10 inactivation for MTB, most of the bacteria required ≤10 min of VUV treatment, 20 min for the influenza viruses while MTB needed about 30 min VUV treatment. This indicated that VUV light is an effective approach against different environmental microorganisms.

Irradiation by a Combination of Different Peak-Wavelength Ultraviolet-Light Emitting Diodes Enhances the Inactivation of Influenza A Viruses

“…Determinate damage of viral RNA was not, however, defined in both those reports and this study. Pyrimidines are more sensitive bases against UV irradiation than purines [32]. UV irradiation generates not only DNA photoproducts such as CPDs, 6-4 pyrimidine-pyrimidone (6-4PP), and cytosine/thymine hydrate [32], but also several RNA photoproducts such as uracil cyclobutane dimer and uracil/cytosine hydrate [33].…”

“…Pyrimidines are more sensitive bases against UV irradiation than purines [32]. UV irradiation generates not only DNA photoproducts such as CPDs, 6-4 pyrimidine-pyrimidone (6-4PP), and cytosine/thymine hydrate [32], but also several RNA photoproducts such as uracil cyclobutane dimer and uracil/cytosine hydrate [33]. We had determined irradiations by 260, 270, and 280 nm UV-LED at the same fluence (4.8 mJ/cm 2 ) in this study, and generated CPDs in herpes simplex virus 1 by dot-blot analysis using anti-CPDs antibody (data not shown).…”

Ultraviolet-C and other methods of decontamination of filtering facepiece N-95 respirators during the COVID-19 pandemic

“…[6][7][8] The mechanism underlying UVGI is the absorption of photons by microbial nucleic acids, causing the formation of pyrimidine photoproducts, 5 which subsequently damage the deoxyribonucleic acid (DNA), 9 prevent replication, and inactivate microorganisms. 10,11 UVGI is commonly produced from a low-pressure mercury lamp source which emits short-wave UVC (100-290 nm), mostly at 254 nm. This is close to the peak emission for bacterial killing, which is 265 nm.…”

“…5 Mercury lamps produce ozone as a byproduct, which itself is a reactive oxygen species that can further inactivate bacteria. 10 These lamps are often used for water and air purification systems. Ozone and free radicals can diffuse into places which are shielded from direct exposure of UV radiation to further inhibit microorganisms.…”

“…Ozone and free radicals can diffuse into places which are shielded from direct exposure of UV radiation to further inhibit microorganisms. 10 Studies have found that the disinfection time required to inactivate bacteriophage MS2 is much lower with light sources emitting UVC and ozone combined than with UVC alone. 12 These systems are limited due to the restrictions related to ozone emission and the toxic effects of ozone on human health.…”