Schaffner, D. W. | bioRxiv Science

bioRxiv2022

The efficiency of Grignard Pure™ to inactivate airborne SARS-CoV-2 surrogate

Grignard Pure (GP) is a unique and proprietary blend of Triethylene Glycol (TEG) and inert ingredients designed for continuous antimicrobial treatment of air. GP received approval from the US EPA under its Section 18 Public Health Emergency Exemption program for use in seven states. This study characterizes the efficacy of GP for inactivating MS2 bacteriophage - a non-enveloped virus widely used as a surrogate for SARs-CoV-2. Experiments measured the decrease in the airborne viable MS2 concentration in the presence of different concentrations of GP from 60 to 90 minutes, accounting for both natural die-off and settling of MS2. Experiments were conducted both by introducing GP aerosol into air containing MS2 and by introducing airborne MS2 into air containing GP aerosol. GP is consistently able to rapidly reduce viable MS2 bacteriophage concentration by 2-3 logs at GP concentrations of 0.02 mg/m3 to 0.5 mg/m3 (corresponding to TEG concentrations of 0.012 mg/m3 to 0.287 mg/m3). Related GP efficacy experiments by the US EPA, as well as GP (TEG) safety and toxicology, are also discussed. SynopsisLimited research on the germicidal properties of triethylene glycol against airborne pathogens was conducted during the 1940s and 50s. This paper investigates the inactivation rate of airborne bacteriophage MS2 by Grignard Pure product, containing a unique and proprietary blend of Triethylene Glycol (TEG) and inert ingredients.

microbiology↗

bioRxiv2021

Higher concentrations of bacterial enveloped virus Phi6 can protect the virus from environmental decay

Phage Phi6 is an enveloped virus considered as a possible non-pathogenic surrogate for SARS-CoV-2 and other viral pathogens in transmission studies. Higher input amounts of bacteriophage Phi6 are shown to delay and protect the phage from environmental decay, both when the phage are dried in plastic tubes, and when they are stored in saline solution at 4{degrees}C. When bacteriophage Phi6 are placed in LB (Luria-Bertani) growth medium prior to placement on the plastic surface, viral recovery is not influenced by the starting concentration. The protection is reflected in longer half-lives of the phage at higher concentrations compared to lower. Because experiments supporting the possibility of fomite transmission of SARS-CoV-2 and other viruses rely upon survival of infectious virus following inoculation of various surfaces, high initial amounts of input virus on a surface may generate artificially inflated survival times compared to realistic lower levels of virus that a subject would normally encounter. This is not only because there are extra half-lives to go through at the higher concentrations, but also because the half-lives themselves are extended at the higher virus concentrations. It is important to design surface drying experiments for pathogens with realistic levels of input virus, and to consider the role of the carrier and matrix if the results are to be clinically relevant. IMPORTANCEDuring the COVID-19 pandemic, a lot of attention has been paid to the environmental decay of SARS-CoV-2 due to proposed transmission of the virus via fomites. However, published experiments have commenced with very high virus titer inoculums, an experimental design not representative of real-life conditions. The study described here evaluated the impact of initial virus titer on environmental decay of an enveloped virus, using a non-pathogenic surrogate for SARS-CoV-2, enveloped bacteriophage Phi6. We establish that higher concentrations of virus can protect the virus from environmental decay, depending on conditions. This has important implications for stability studies of SARS-CoV-2 and other viruses. Our results point to a limitation in the fundamental methodology that has been used to attribute fomite transmission for almost all respiratory viruses.

microbiology↗