Inactivation of Vaccinia Virus by Natural Sunlight and by Artificial UVB Radiation

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The inactivation of pathogenic aerosols by solar radiation is relevant to public health and biodefense. We investigated whether a relatively simple method to calculate solar diffuse and total irradiances could be developed and used in environmental photobiology estimations instead of complex atmospheric radiative transfer computer programs. The second-order regression model that we developed reproduced 13 radiation quantities calculated for equinoxes and solstices at 35(°) latitude with a computer-intensive and rather complex atmospheric radiative transfer program (MODTRAN) with a mean error <6% (2% for most radiation quantities). Extending the application of the regression model from a reference latitude and date (chosen as 35° latitude for 21 March) to different latitudes and days of the year was accomplished with variable success: usually with a mean error<15% (but as high as 150% for some combination of latitudes and days of year). This accuracy of the methodology proposed here compares favorably to photobiological experiments where the microbial survival is usually measured with an accuracy no better than ±0.5 log10 units. The approach and equations presented in this study should assist in estimating the maximum time during which microbial pathogens remain infectious after accidental or intentional aerosolization in open environments.

Section: Discussionmentioning

confidence: 99%

Regression Model for Estimating Inactivation of Microbial Aerosols by Solar Radiation

Ben‐David

Sagripanti

2013

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“…In river systems, constant fluence is unlikely, because microorganisms move within the water column and sunlight intensity changes with respect to time of day and ambient meteorological conditions. Moreover, as most UV‐B is delivered during a 4‐hour period (2 h either side of solar noon) a constant fluence cannot be assumed .…”

Section: Resultsmentioning

confidence: 99%

“…A previously proposed model suggested that approximately 41 times the fluence of UV‐C would be required to inactivate viruses by the same magnitude when using UV‐B ; for the Vaccina virus, 33 times more UV‐B was required than UV‐C to achieve the same level of inactivation by the same authors . This factor has been used in biodefense calculations and influenza epidemic risk assessments .…”

Section: Resultsmentioning

confidence: 99%

“…Whether delivered naturally via solar radiation (UV‐A and UV‐B), or artificially through disinfection technologies (UV‐C), the inactivating effect of UV radiation on microorganisms has been widely studied and previously reported , and is thought to be the primary means of environmental viral degradation in many systems . The influence of UV‐A and UV‐B radiation on microorganisms in the environment is particularly important when the organisms studied are indicators of fecal contamination, or surrogates for infectious agents of significance to human health, as is often the case in microbial source tracking (MST) and quantitative microbial risk assessment (QMRA) studies.…”

Section: Introductionmentioning

confidence: 99%

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Inactivation of Bacteriophage Infecting Bacteroides Strain GB124 Using UV‐B Radiation

Diston

Ebdon

Taylor

2014

Ultraviolet-B radiation (280-320 nm) has long been associated with the inactivation of microorganisms in the natural environment. Determination of the environmental inactivation kinetics of specific indicator organisms [used as tools in the field of microbial source tracking (MST)] is fundamental to their successful deployment, particularly in geographic regions subject to high levels of solar radiation. Phage infecting Bacteroides fragilis host strain GB124 (B124 phage) have been demonstrated to be highly specific indicators of human fecal contamination, but to date, little is known about their susceptibility to UV-B radiation. Therefore, B124 phage (n = 7) isolated from municipal wastewater effluent, were irradiated in a controlled laboratory environment using UV-B collimated beam experiments. All B124 phage suspensions possessed highly similar first order log-linear inactivation profiles and the mean fluence required to inactivate phage by 4 - log(10) was 320 mJ cm(-2). These findings suggest that phage infecting GB124 are likely to be inactivated when exposed to the levels of UV-B solar radiation experienced in a variety of environmental settings. As such, this may limit the utility of such methods for determining more remote inputs of fecal contamination in areas subject to high levels of solar radiation.

“…The setup used to expose P.aeruginosa to direct sunlight was similar to that previously described for exposing virulent B. pseudomallei and vaccinia virus . A 100 μl aliquot of the bacterial stock washed twice in sterile distilled water was dispensed in the middle of an UV‐transparent petri dish (Lumox UV‐permaeable 50TC, sterile; Greiner Bio‐One, cat# 96077440, Göttingen, Germany), covered with the UV‐transparent lid and the edges very safely sealed with parafilm.…”

Section: Methodsmentioning

confidence: 99%

Inactivation of Pseudomonas aeruginosa by Direct Sunlight

Sagripanti¹,

Grote

Niederwöhrmeier

et al. 2013

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We determined the sensitivity of Pseudomonas aeruginosa to direct sunlight radiation, while maintaining the experimental temperature below levels harmful to the bacterium. The results presented here were similar to previous data on solar sensitivity obtained half a world away on another related bacterial species. The findings presented in this study suggest that related bacteria have a characteristic sensitivity to sunlight with their survival depending mainly on the fluence (photons) received in a dose-dependent manner that is otherwise relatively independent from latitude, atmospheric ozone and other local conditions. Conditions that inactivated P. aeruginosa did not result in measurable impairment of specific polymerase chain reaction (PCR) or enzyme-linked immunoassays (ELISA) tests suggesting that this germ could still be amenable to detection after inactivation by sunlight. The results presented in this study should assist in predicting the survival of P. aeruginosa outdoors and in monitoring the risk posed by this widespread organism in a variety of environmental settings.