Carolina S.F. Xavier

Bio: Carolina S.F. Xavier is an academic researcher from University of Porto. The author has contributed to research in topics: Coronavirus & Personal protective equipment. The author has co-authored 1 publications.

Inactivation of aerosolized SARS‐CoV‐2 by 254 nm UV‐C irradiation

Abstract: Abstract Surface residing SARS‐CoV‐2 is efficiently inactivated by UV‐C irradiation. This raises the question whether UV‐C‐based technologies are also suitable to decontaminate SARS‐CoV‐2‐ containing aerosols and which doses are needed to achieve inactivation. Here, we designed a test bench to generate aerosolized SARS‐CoV‐2 and exposed the aerosols to a defined UV‐C dose. Our results demonstrate that the exposure of aerosolized SARS‐CoV‐2 with a low average dose in the order of 0.42–0.51 mJ/cm2 UV‐C at 254 nm resulted in more than 99.9% reduction in viral titers. Altogether, UV‐C‐based decontamination of aerosols seems highly effective to achieve a significant reduction in SARS‐CoV‐2 infectivity.

Effect of ultraviolet C emitted from KrCl excimer lamp with or without bandpass filter to mouse epidermis

Abstract: It has been reported that 222-nm ultraviolet C (UVC) exerts a germicidal effect on bacteria and viruses as well as UV radiation emitted from a conventional germicidal lamp but is less toxic to the mammalian cells than that from a germicidal lamp. An excimer lamp filled with krypton chloride (KrCl) gas principally emits 222-nm UVC. However, the lamp also emits a wide band of wavelengths other than 222 nm, especially UVC at a longer wavelength than 222 nm and ultraviolet B, which cause DNA damage. There are some reports on the critical role of bandpass filters in reducing the harmful effect of UVC emitted from a KrCl excimer lamp in a human skin model and human subjects. However, the effectiveness of a bandpass filter has not been demonstrated in animal experiments. In the present study, mice were irradiated with UVC emitted from a KrCl excimer lamp with or without a bandpass filter. UVC emitted from an unfiltered KrCl lamp at doses of 50, 150 and 300 mJ/cm2 induced cyclobutyl pyrimidine dimer (CPD)-positive cells, whereas UVC emitted from a filtered lamp did not significantly increase CPD-positive cells in the epidermis. The present study suggested that the bandpass filter serves a critical role in reducing the harmful effect of emission outside of 222 nm to mouse keratinocytes.

The Effectiveness of Ultraviolet-C (UV-C) Irradiation on the Viability of Airborne Pseudomonas aeruginosa

Abstract: Pseudomonas aeruginosa (Pa) is the predominant bacterial pathogen in people with cystic fibrosis (CF) and can be transmitted by airborne droplet nuclei. Little is known about the ability of ultraviolet band C (UV-C) irradiation to inactivate Pa at doses and conditions relevant to implementation in indoor clinical settings. We assessed the effectiveness of UV-C (265 nm) at up to seven doses on the decay of nebulized Pa aerosols (clonal Pa strain) under a range of experimental conditions. Experiments were done in a 400 L rotating sampling drum. A six-stage Andersen cascade impactor was used to collect aerosols inside the drum and the particle size distribution was characterized by an optical particle counter. UV-C effectiveness was characterized relative to control tests (no UV-C) of the natural decay of Pa. We performed 112 tests in total across all experimental conditions. The addition of UV-C significantly increased the inactivation of Pa compared with natural decay alone at all but one of the UV-C doses assessed. UV-C doses from 246–1968 µW s/cm2 had an estimated effectiveness of approximately 50–90% for airborne Pa. The effectiveness of doses ≥984 µW s/cm2 were not significantly different from each other (p-values: 0.365 to ~1), consistent with a flattening of effectiveness at higher doses. Modelling showed that delivering the highest dose associated with significant improvement in effectiveness (984 µW s/cm2) to the upper air of three clinical rooms would lead to lower room doses from 37–49% of the 8 h occupational limit. Our results suggest that UV-C can expedite the inactivation of nebulized airborne Pa under controlled conditions, at levels that can be delivered safely in occupied settings. These findings need corroboration, but UV-C may have potential applications in locations where people with CF congregate, coupled with other indoor and administrative infection control measures.

Airborne murine coronavirus response to low levels of hypochlorous acid, hydrogen peroxide and glycol vapors

Abstract: Abstract Airborne murine coronavirus was assessed for its sensitivity to the vapors of chemicals commonly used to disinfect indoor surfaces. As a model for the chemical sensitivity of airborne SARS-CoV-2, the infectious potential of airborne Mouse Hepatitis Virus (MHV) was tracked in the presence of the following pure chemical vapors, each of which was below its permissible exposure limit (PEL) as regulated by the US National Institute of Occupational Safety and Health (NIOSH): <50 ppmv for glycol; <1ppmv for HOCl; and <1ppmv for H2O2. Along with its growth media, infectious MHV was aerosolized in a particle size distribution between 0.5 μm and 3.2 μm into a sealed, dark, 9 m3 chamber maintained at 22°C and 60% RH, including levels of chemical vapors maintained below their respective PELs. As judged by the TCID50 of airborne MHV collected by condensation, this airborne virus was rapidly inactivated by HOCl vapor, incurring an average of 99% infectious potential loss after 16 ± 4 min exposure to ≤0.2 ppmv HOCl. Airborne MHV responded with a 99% loss of infectious potential in 38 ± 10 min of exposure to ≤0.9 ppmv H2O2; and, a 99% loss of infectious potential in 33 ± 15 min when exposed to a gas-phase dipropylene glycol blend ≤20 ppmv as TVOC. The juxtaposition of quantitative RT-PCR and TCID50 responses suggest that even low levels of gas-phase HOCl exposures can damage the genome of airborne coronavirus in relatively short time frames (c.a. <5 mins).