In a recent study published in bioRxiv* preprint server, researchers have characterized the efficacy of Grignard Pure™ (GP) in inactivating bacteriophage MS2. This non-enveloped viral microbe has been widely used as a surrogate for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Additional layers of protection need to be developed to minimize exposure to SARS-CoV-2 and reduce the incidence of coronavirus disease 2019 (COVID-19). GP is a blend of triethylene glycol (TEG), propylene glycol and water designed to provide a permanent antimicrobial air treatment. However, the efficacy of TEGs against airborne pathogens needs to be investigated.
About the study
In the present study, the investigators examined the inactivation rate of MS2 (ATCC 15597-B1) with undiluted GP.
Experiments were carried out to measure the reduction in viable MS2 concentrations in air in the presence of several concentrations of GP, which ranged from 0.02 mg/m3 to 0.5 mg/m3. The corresponding TEG concentration range was from 0.01 mg/m3 to 0.29 mg/m3. 60 minutes to 90 minutes including natural dying and settling (NDOS) MS2.
The experiments were carried out in two laboratories either by introducing aerosol HP into air containing MC2 or by introducing MC2 into aerosol air containing HP. Aerosols of GP were prepared using vaporizers or nebulizers for a single short burst of GP (four seconds) or for a controlled release of GP with GP administered intermittently to maintain a certain concentration.
The mass concentrations of aerosol HP correlated with the total concentrations of TEGs (vapors and aerosols) in the air. coli at 10 o’clock9 concentrations of colony forming units (CFU)/ml and MS2 in >10eleven plaque forming unit (PFU)/mL concentrations were used as hosts for all experiments. The amount of PFU in the samples was converted to concentration in air (PFU/m3).
The two laboratories used slightly different virus preparation protocols and different MS2 starting concentrations. The first lab used 3.4 x 10eight PFU/m3, while the second laboratory used 6.7 x 10ten PFU/m3. In addition, the GP was also evaluated by the U.S. Environmental Protection Agency (EPA) Research and Development Office between May and June 2021.
Results
With a four second GP burst, viable MS2 concentrations decreased by 30% (0.2 log) at 0.5 minutes and reached 90% (>1 log) at 60 minutes due to NDOS. The observed complete MS2 inactivation was 99.9% (three logs) at 0.5 minutes and 99.99% (four logs) at 15 minutes and 60 minutes. A net 2.6 log reduction in MS2 concentration in the aerosol was observed 0.5 minutes after GP treatment.
After 15 minutes, the first laboratory found a net decrease in the viable MS2 concentration of 2.9 log, while the second laboratory reported 3.2. After one hour of GP therapy, both laboratories reported a slightly smaller net decrease compared to those observed after 15 minutes (2.4) in the first laboratory and 3.0 in the second laboratory. The data obtained from both laboratories were found to be in good agreement with each other.
The overall log reduction at 0.5 and 15 minutes was 2.6 and 3.0, respectively, indicating 99.9% elimination of MS2. The logarithmic reduction in viable concentrations of MS2 and GP therapy showed statistically significant differences.
Controlled release GP showed high efficacy with a 1.0 to 2.5 net log reduction in viable MS2 concentrations among samples initiated 30 seconds after GP therapy. Among the samples obtained, the overall log reduction ranged from 2.0 (corresponding TEG concentration was 0.06 mg/m3) to 3.1 (corresponding TEG concentration was 0.29 mg/m3).
For the 0.5 minute and 15 minute sampling time points, inactivation was higher at higher TEG concentrations. At a sampling time of 60 minutes, the overall log reduction was either the same (TEG concentration = 0.06 mg/m3), higher (TEG = 0.19 and 0.24 mg/m3), or slightly reduced (i.e. TEG = 0.29 mg/m3). When pooling all the data together, regardless of GP concentration, the log reduction in MS2 concentration after GP therapy showed a statistically significant difference compared to the log reduction in airborne viable MS2 concentrations due to NDOS for all three selected time points.
At the 15-minute sampling step, the reduction reported by the US Environmental Protection Agency was 96% and 99.8% (1.3 logs and 2.6 logs), comparable between the two laboratories. Both test scenarios showed a larger percentage reduction in the number of viable MS2s over time. After 60 minutes, EPA testing showed a 98% (1.6 log) reduction, with the first lab reporting a 99.8% (or 2.7 log) reduction. Data from the second scenario showed similar declining trends in MS2 concentrations in the second laboratory and in the US Environmental Protection Agency.
In conclusion, three sets of experiments demonstrated the effectiveness of HP (at concentrations from 0.02 mg/m3 to 0.5 mg/m3, corresponding to TEG concentrations from 0.01 mg/m3 to 0.29 mg/m3) against airborne viruses. such as bacteriophage MS2, a surrogate for SARS-Cov-2. GP can be safely used as an additional layer of protection as an antimicrobial agent to prevent indoor airborne transmission of pathogens.
*Important note
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered definitive, guiding clinical practice/health-related behavior, or considered as established information.