Establishment and utilization of an evaluation system for virucidal activity of disinfectants against a coronavirus with apparent applicability to SARS-CoV-2

Evaluation of chlorine dioxide in liquid state and in gaseous state as virucidal agent against avian influenza virus and infectious bronchitis virus

The antiviral activity of chlorine dioxide (ClO2) in liquid (ClO2 gas dissolved liquid) and gaseous state against avian influenza virus (AIV) and infectious bronchitis virus (IBV) was evaluated. To evaluate the effect of ClO2 in liquid state, suspension tests (10 ppm) and carrier tests in dropping / wiping techniques (100 ppm) were performed. In the suspension test, virus titers were reduced below the detection limit within 15 sec after treatment, in spite of the presence of an accompanying organic matter. In the carrier test by dropping technique, AIV and IBV were reduced to below the detection limit in 1 and 3 min, respectively. Following wiping technique, no virus was detected in the wiping sheets after 30 sec of reaction. Both viruses adhering to the carriers were also reduced by 3 logs, thereby indicating that they were effectively inactivated. In addition, the effect of ClO2 gas against IBV in aerosols was evaluated. After the exposure of sprayed IBV to ClO2 gas for a few seconds, 94.2% reduction of the virus titer was observed, as compared to the pre-treatment control. Altogether, hence, ClO2 has an evident potential to be an effective disinfectant for the prevention and control of AIV and IBV infections on poultry farms.

Evaluation of antimicrobial efficacies of chlorine dioxide gas released into the air towards pathogens present on the surfaces of inanimate objects

The efficacy of ClO2 gas, as surface disinfectant at around 1,000 ppb against avian orthoavulaviruses type 1 (AOAV-1), infectious bronchitis virus (IBV), Escherichia coli (EC), and Salmonella Enteritidis (SE) was evaluated at the required level (≥99.9% reduction) on various surfaces. Exposing the surfaces to ClO2 gas for 1 hr reduced AOAV-1, except for rayon sheets which required 3 hr. However, 1 hr of exposure did not effectively reduced IBV titer. In the case of EC, glass plates and plastic carriers needed 1 hr of exposure, while rayon sheets required 2 hr. SE on rayon sheets required 1 hr exposure, but on the other tested surfaces showed inadequate reduction. Overall, ClO2 gas is an effective disinfectant for poultry farms.

Quaternary ammonium compounds of emerging concern: Classification, occurrence, fate, toxicity and antimicrobial resistance

Amplified hygiene and precautionary measures are of utmost importance to control the spread of COVID-19 and future infection; however, these changes in practice are projected to trigger a rise in the purchase, utilisation and hence, discharge of many disinfectants into the environment. While alcohol-based, hydrogen peroxide-based, and chlorine-based compounds have been used widely, quaternary ammonium compounds (QACs) based disinfectants are of significant concern due to their overuse during this pandemic. This review presents the classification of disinfectants and their mechanism of action, focusing on QACs. Most importantly, the occurrence, fate, toxicity and antimicrobial resistance due to QACs are covered in this paper. Here we collated evidence from multiple studies and found rising trends of concern, including an increase in the mass load of QACs at a wastewater treatment plant (WWTP) by 331% compared to before the COVID-19 pandemic, as well as an increases in the concentration of 62% in residential dust, resulting in high concentrations of QACs in human blood and breast milk and suggesting that these could be potential sources of persistent QACs in infants. In addition to increased toxicity to human and aquatic life, increased use of QACs and accelerated use of antibiotics and antimicrobials during the COVID-19 pandemic could multiply the threat to antimicrobial resistance.

Isolation, molecular characterization, and disinfectants susceptibility of swine-carried mammalian orthoreoviruses in Japan in 2020-2022

Biosecurity enhancement contributes to the reduction of various microbial pathogens. Mammalian orthoreoviruses (MRVs) which are increasingly recognized as potentially serious problems on swine industry were used as indicators of biosecurity enhancement on two pig farms. Twelve MRVs were detected and isolated from fecal specimens of healthy pigs collected from one of the two farms in Japan. By sequencing based on the partial S1 gene, MRV isolates were classified as MRV1 and MRV2. Additionally, the virucidal activities of disinfectants toward the isolated MRV1 were evaluated using quaternary ammonium compound (QAC) diluted 500 times with water (QAC-500), 0.17% food additive glade calcium hydroxide (FdCa(OH)₂) solution, QAC diluted with 0.17% FdCa(OH)₂ solution (Mix-500), sodium hypochlorite at 100 or 1,000 parts per million (ppm) of total chlorine (NaClO-100 or NaClO-1000, respectively). To efficiently inactivate MRV1 (≥3 log₁₀ reductions), 0.17% FdCa(OH)₂, Mix-500 and NaClO-1000 required 5 min, whereas it took 30 min for QAC-500. The number of MRV detections has decreased over time, after using Mix-500 for disinfection on the positive farm. These results suggest that different serotypes of MRVs are circulating among pigs, and that the occurrence of MRVs in the farms decreased consequent to more effective disinfection.

Evaluation of Virucidal Quantitative Carrier Test towards Bovine Viruses for Surface Disinfectants While Simulating Practical Usage on Livestock Farms

Livestock farming is affected by the occurrence of infectious diseases, but outbreaks can be prevented by effective cleaning and disinfection along with proper farm management. In the present study, bovine coronavirus (BCoV) and bovine rotavirus A (RVA) were inactivated using food additive-grade calcium hydroxide (FdCa(OH)2) solution, quaternary ammonium compound (QAC) and their mixture through suspension tests as the primary screening, and afterward via carrier tests using dropping or dipping techniques as the secondary screenings. Viruses in the aqueous phase can be easily inactivated in the suspension tests, but once attached to the materials, they can become resistant to disinfectants, and require longer times to be inactivated. This highlights the importance of thorough cleaning with detergent before disinfection, and keeping elevated contact durations of proper disinfectants to reduce viral contamination and decrease infectious diseases incidence in farms. It was also reaffirmed that the suspension and carrier tests are necessary to evaluate disinfectants and thus determine their actual use. Particularly, the mixture of QAC and FdCa(OH)2 was found to exhibit synergistic and broad-spectrum effects compared to their use alone, and is now recommended for use on livestock farms.

Universal Virucidal Activity of Calcium Bicarbonate Mesoscopic Crystals That Provides an Effective and Biosafe Disinfectant

We investigated the virucidal effects in solution of a new type of disinfectant, calcium bicarbonate mesoscopic crystals, designated CAC-717, against various types of virus. CAC-717 in solution is alkaline (pH 12.4) and has a self-electromotive force that generates pulsed electrical fields. Upon application to human skin, the pH of the solution becomes 8.4. CAC-717 contains no harmful chemicals and is thus non-irritating and harmless to humans and animals. Its virucidal effects were tested against six types of animal virus: enveloped double-strand (ds)-DNA viruses, non-enveloped ds-DNA viruses, non-enveloped single strand (ss)-DNA viruses, enveloped ss-RNA viruses, non-enveloped ss-RNA viruses, and non-enveloped ds-RNA viruses. The treatment resulted in a reduction in viral titer of at least 3.00 log₁₀ to 6.38 log₁₀. Fetal bovine serum was added as a representative organic substance. When its concentration was ≥20%, the virucidal effect of CAC-717 was reduced. Real-time PCR revealed that CAC-717 did not reduce the quantity of genomic DNA of most of the DNA viruses, but it greatly reduced that of the genomic RNA of most of the RNA viruses. CAC-717 may therefore be a useful biosafe disinfectant for use against a broad range of viruses.

Rapid in vitro virucidal activity of slightly acidic hypochlorous acid water toward aerosolized coronavirus in simulated human-dispersed droplets

The virucidal activities were evaluated by spraying slightly acidic hypochlorous acid waters (SAHWs) containing various concentrations of free available chlorine - 100, 200, 300 and 500 ppm (SAHW-100, -200, -300 and -500, respectively) - toward aerosol of an avian coronavirus (infectious bronchitis virus: IBV). The viral solution was supplemented with 0.5% fetal bovine serum (FBS) to simulate normal human droplets generated by sneezing or coughing in a real-life scenario. The virus containing 0.5% FBS was sprayed and exposed to SAHWs for a few seconds in a closed chamber, before reaching the air sampler. The results showed that IBV exposed to SAHW-100 and -200 for a few seconds decreased by 0.21 log₁₀ and 0.80 log₁₀, respectively, compared to the pre-exposed samples to SAHWs as controls. On the other hand, reductions of 1.16 log₁₀ and 1.67 log₁₀ were achieved following the exposure to SAHW-300 and -500, respectively, within a few seconds. These results suggest that SAHWs have rapid in vitro virucidal activity toward aerosolized IBV. The findings obtained for IBV might basically be applicable in relation to SARS-CoV-2, given the resemblance between the two viruses. To prevent human-to-human transmissions by aerosols, the inactivation of viruses in the air by exposure to SAHWs for a few seconds seems to be an effective way.

Synergistic effects of quaternary ammonium compounds and food additive grade calcium hydroxide on microbicidal activities at low temperatures

The microbicidal activities of mixtures of quaternary ammonium compounds (QACs) and food additive grade calcium hydroxide (FdCa(OH)₂) were evaluated in a suspension test at −20°C using an anti-freeze agent (AFA) containing methanol, or at 1°C, with varying contact time, toward avian influenza virus (AIV), Newcastle disease virus (NDV), fowl adenovirus (FAdV), avian reovirus (ARV), Salmonella Infantis (SI) and Escherichia coli (EC). At −20°C, the mixtures could inactivate AIV and NDV within 30 min, FAdV and ARV within 5 sec, and SI and EC within 3 min, respectively. AFA did not inactivate viruses and bacteria within 30 min and 10 min, respectively. At 1°C, the mixtures inactivated FAdV and ARV within 30 sec, AIV within 10 min, and NDV within 30 min. A mixture of slaked lime (SL) and QAC could inactivate FAdV and ARV within 30 sec, but could not inactivate AIV and NDV even after 60 min at 1°C. SL could not substitute FdCa(OH)₂ in order to exert the synergistic effects with QAC. Thus, QACs microbicidal activities were maintained or enhanced by adding FdCa(OH)₂. It is hence recommended to use QACs with FdCa(OH)₂, especially in the winter season.

Virucidal activity of slightly acidic hypochlorous acid water toward influenza virus and coronavirus with tests simulating practical usage

Slightly acidic hypochlorous acid waters (SAHWs) with pH of 5.2-5.8 containing different concentrations of free available chlorine - 62, 119, 220, 300, and 540 ppm (SAHW-62, -119, -220, -300, and -540, respectively) - were evaluated for their virucidal activity toward a low pathogenic H7N1 avian influenza virus (AIV) and an infectious bronchitis virus (IBV) in suspension, abiotic carrier, and direct spray tests, with the presence of organic materials. In the carrier test, the dropping and wiping techniques were performed toward viruses on carriers. In the suspension test, SAHW-62 could decrease the viral titer of both AIV and IBV by more than 1000 times within 30 s. With the dropping technique, IBV on carriers showed high resistance to SAHW, while AIV on plastic carrier was inactivated to an effective level (≧3 log virus reduction) within 1 min. With the wiping technique, SAHW-62 could inactivate both AIV and IBV on wiped plastic carriers to an effective level within 30 s. However, SAHW-220 could not inactivate IBV in the wiping rayon sheet to an effective level. In the direct spray test, sprayed SAHW-300 within 10 min, and SAHW-540 within 20 min, inactivated AIV and IBV on the rayon sheets to undetectable level, respectively. Our study indicates that the usage of wipes with SAHW could remove viruses from plastic carriers, while viruses remained in the wipes. Besides, a small volume of sprayed SAHW was effective against the viruses on the rayon sheets for daily cleaning in the application area. The findings we obtained concerning IBV might basically be applicable in relation to SARS-CoV-2, given the resemblance between the two viruses.