Bactericidal and virucidal efficacies of food additive grade calcium hydroxide under various concentrations, organic material conditions, exposure duration, and its stability

Gastrointestinal bacteria growth inhibition by a toilet sanitary good for disaster shelter

Japan has experienced several large earthquakes in the past 30 years. Emergency evacuation shelters become overcrowded immediately after disasters. Deteriorating sanitary conditions in toilets are associated with a higher risk of infectious pathogen transmission. "Ho!Toilet" is a toilet sanitary good for emergency evacuation shelters. Its main ingredients are calcium hydroxide, superabsorbent polymer (SAP), and zeolite. SAP absorbs water and solidifies waste for proper disposal. Zeolites are deodorizers. Calcium hydroxide, which inactivates microorganisms, can reduce the risk of infectious diseases in evacuation shelters. In this study, we designed experiments to confirm the antimicrobial effects of the Ho!Toilet. Escherichia coli (E.coli), Vibrio cholerae (V. cholerae), and Clostridioides difficile (C. difficile) were selected as the microorganisms for this study. Two strains of E. coli and two strains of V. cholerae were inactivated, whereas, C. difficile was not. After the Ho!Toilet powder and bacterial solutions were mixed and stirred, the mixture was separated into a gel and a liquid phase. The pH values in the gel and the liquid phase were 12.0 and 9.3, respectively. After centrifugation of these mixtures, the supernatants were cultured with bacteria at pH 10.7. Ho!Toilet inactivates bacteria other than C. difficile in this study. These effects are mainly achieved under alkaline conditions using calcium hydroxide. Considering the additional effects of the ingredients in Ho!Toilet, SAP, and Zeolite, these products would be useful in toilets with poor sanitary conditions, such as evacuation shelters, to prevent the transmission of infectious diseases.

Effectiveness of potassium peroxymonosulfate against enveloped viruses using an aqueous phase and its application on various contaminated carrier surfaces and artificially avian influenza virus-contaminated clothes

Background and Aim

Potassium peroxymonosulfate (PPMS) is a broad-spectrum disinfectant that oxidizes viral protein capsids. The effectiveness of PPMS in killing viruses depends on several factors, including its concentration, contact time, and present of organic materials. This study evaluated the efficacy of PPMS in an aqueous phase. It also applied PPMS to artificially avian influenza virus (AIV)-contaminated carrier surfaces and clothes and compared its effectiveness with that of sodium dichloroisocyanurate (NaDCC) and quaternary ammonium compounds (QAC).

Materials and Methods

Four PPMS concentrations (1×, 0.5×, 0.25×, and 0.125×), were evaluated for their virucidal efficacy against Newcastle disease virus (NDV) and AIV in an aqueous phase. The evaluation included testing in the absence and presence of organic materials under different exposure times, such as 5 s, 30 s, 1 min, 3 min, 5 min, 10 min, and 15 min. AIV inactivation was assessed on contaminated carrier surfaces, such as stainless steel, rubber, plastic, and artificially contaminated clothes.

Results

In aqueous phase, concentrations of 1×, 0.5×, 0.25×, and 0.125× inactivated NDV in the absence of organic materials within 5 s, 5 s, 5 min, and 15 min at concentrations of 1×, 0.5×, 0.25×, and 0.125×, respectively. In the presence of organic material contamination, NDV could be inactivated within 30 s for 1×, 1 min for 0.5×, and 10 min for 0.25×; however, 0.125× PPMS did not achieve inactivation within 15 min. PPMS concentrations of 1×, 0.5×, 0.25×, and 0.125× inactivated AIV within 5 s, 5 s, 5 s, and 30 s, respectively, in both the absence and presence of organic materials. PPMS at a concentration of 1× could inactivate AIV on all carriers within 30 s. PPMS at 0.5× and 0.25× concentrations could inactivate AIV within 30 s on rubber and plastic; inactivation occurred within 1 min on stainless steel. However, 0.125× PPMS and 1× QAC could not achieve inactivation within 3 min on all carriers. Finally, PPMS concentrations of 1×, 0.5×, 0.25×, and 0.125× inactivated AIV on rayon sheets within 5 s, 30 s, 5 min, and 15 min, respectively. However, the recommended NaDCC concentration achieved inactivation within 10 min, whereas QAC did not achieve inactivation within 15 min.

Conclusion

PPMS can inactivate enveloped viruses such as NDV and AIV. Furthermore, PPMS is superior to NaDCC and QAC for inactivating viruses on various carrier surfaces and artificially contaminated clothes. However, the virucidal efficacy of PPMS depends on the optimal concentration, organic material conditions, and exposure/contact timing. Therefore, PPMS is a promising alternative disinfectant crucial for enhancing biosecurity and controlling viruses that contaminate animal farms, slaughterhouses, and hospitals.

Stability and Detection Limit of Avian Influenza, Newcastle Disease Virus, and African Horse Sickness Virus on Flinders Technology Associates Card by Conventional Polymerase Chain Reaction

The Flinders Technology Associates (FTA) card, a cotton-based cellulose membrane impregnated with a chaotropic agent, effectively inactivates infectious microorganisms, lyses cellular material, and fixes nucleic acid. The aim of this study is to assess the stability and detection limit of various RNA viruses, especially the avian influenza virus (AIV), Newcastle disease virus (NDV), and African horse sickness virus (AHSV), on the FTA card, which could significantly impact virus storage and transport practices. To achieve this, each virus dilution was inoculated onto an FTA card and stored at room temperature in plastic bags for durations ranging from 1 week to 6 months. Following storage, the target genome was detected using conventional reverse transcription polymerase chain reaction. The present study demonstrated that the detection limit of AIV ranged from 1.17 to 6.17 EID50 values over durations ranging from 1 week to 5 months, while for NDV, it ranged from 2.83 to 5.83 ELD50 over the same duration. Additionally, the detection limit of AHSV was determined as 4.01 PFU for both 1 and 2 weeks, respectively. Based on the demonstrated effectiveness, stability, and safety implications observed in the study, FTA cards are recommended for virus storage and transport, thus facilitating the molecular detection and identification of RNA viral pathogens.

Sensitivity of RNA viral nucleic acid-based detection of avian influenza virus, Newcastle disease virus, and African horse sickness virus on flinders technology associates card using conventional reverse-transcription polymerase chain reaction

Background and Aim

The flinders technology associates (FTA) card is a cotton-based cellulose membrane impregnated with a chaotropic agent that inactivates infectious microorganisms, lyses cellular material, and fixes DNA and/or RNA within the fiber matrix. However, little is known about the effectiveness of these cards for detecting RNA viruses in animals. This study aimed to evaluate the sensitivity of RNA virus detection using conventional reverse-transcription polymerase chain reaction (RT-PCR) on FTA cards.

Materials and Methods

A highly virulent Newcastle disease virus (NDV) and an avian influenza virus (AIV) with low pathogenicity were propagated using chicken embryonic eggs. Three days after inoculation, the allantoic fluid was harvested, stored at -80°C, and the stock virus was tested for virus titration. African horse sickness virus (AHSV) was obtained from a live attenuated vaccine that was dissolved and stored at -80°C. For sample preparation, each stock virus was 10-fold serially diluted and each dilution was inoculated onto an FTA card, followed by drying in a Class II safety cabinet. Both the stock virus and infected FTA card were genomically isolated using an extraction kit, FTA purification kit, and extraction kit with Tris-EDTA (TE) buffer. The target genome was then detected by one-step RT-PCR for NDV and AIV, and two-step RT-PCR for African horse sickness, including gel electrophoresis for the detection of specific nucleic acids.

Results

The detection limit of stock AIV was compared on FTA cards, using the FTA purification kit, and with TE buffer with an extraction kit. The corresponding results were 1.47, 1.17, and 2.18 log₁₀ EID₅₀, respectively, while for NDV the results were 4.13, 4.83, and 4.84 log₁₀ ELD₅₀. Finally, detection limit of stock AHSV and AHSV on the FTA card extracted using TE buffer with an extraction kit were 4.30 and 4.01 log₁₀ plaque-forming units, respectively.

Conclusion

This study demonstrated that the detection limit or sensitivity of all tested RNA viruses on FTA cards did not differ when compared with those of the stock virus and in both methods for RNA isolation on FTA cards. These cards are suitable for collecting and transporting samples infected with RNA viruses, particularly AIV, NDV, and AHSV. Flinders technology associates cards also provide hazard-free samples, a reliable source of RNA for molecular characterization, and sufficient quantity for diagnostic applications based on nucleic acid-based detection.

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.

Farm use of calcium hydroxide as an effective barrier against pathogens

Livestock farming is affected by the occurrence of infectious diseases, but outbreaks can be prevented by proper sanitary control measures. Calcium hydroxide (Ca(OH)₂), commonly called slaked lime, powder is traditionally used as a disinfectant to prevent infectious diseases in livestock. Since Ca(OH)₂ can inactivate a wide variety of pathogens, has a small environmental impact, does not require a disinfection tank (i.e., can be spread directly on the ground) and is produced inexpensively worldwide, it is used for the prevention of epidemics on farms worldwide. Water is essential for the strong alkalinity that underlies its disinfecting effect, but it is unknown how much water is required under field conditions. In addition, Ca(OH)₂ reacts with carbon dioxide in the environment, reducing its pH, but it is unclear how long its degradation takes under actual field use. Thus, we measured the water adsorption ability of Ca(OH)₂-based disinfectants and its relation to disinfectant activity, as assessed by colony counts and live/dead staining and observation. We found that 15–20% (w/w) water in Ca(OH)₂ was necessary for disinfection to occur in practice. Moreover, we found that the pH of Ca(OH)₂ decreased within about two weeks to one month under actual use in practical conditions and lost its ability to disinfect. We further showed that granules prepared from Ca(OH)₂ and zeolite maintained high alkalinity more than twice as long as calcium powder. These findings will help to establish a suitable method of applying Ca(OH)₂ to protect farms from infectious diseases.