Effective Disinfection Method Research Articles

Regulating facility soil microbial community and reducing cadmium enrichment in lettuce by reductive soil disinfestation

The accumulation of cadmium (Cd) in facility soil is attracting increasing attention. Reductive soil disinfestation (RSD) is an effective soil disinfection method, while also having a certain passivating effect on Cd. The application of organic matter is crucial for the success of RSD, but the reduction efficiencies of different organic materials vary. Here, five treatments, namely untreated soil (CK), bean dregs (BD), peanut dregs (PD), sesame dregs (SD), and apple dregs (AD) were applied, and their performances in Cd immobilization in Cd-contaminated soil were assessed. Changes in soil properties and microbial communities were monitored. The results showed that the overall soil pH following RSD treatment decreased significantly, while organic matter, hydrolyzed nitrogen, available phosphorus, available potassium, exchangeable calcium, and exchangeable magnesium increased significantly. Compared to CK, the exchangeable (EX)-Cd contents after treatments SD and AD significantly decreased by 25.4% and 23.7%, respectively. RSD led to significant changes in the composition of soil microbial communities. SD treatment significantly increased the number of soil fungal operational taxonomic units (OTU), while BD, PD, and SD significantly increased the relative abundances of Bacteroidetes, Chloroflexi, Deinococus Thermus, and Basidiomycota in bacterial communities. The Gemmatimonadetes phylum showed a highly significant negative correlation with EX-Cd, indicating that it might have a positive effect on the fixation of Cd in polluted soil. SD significantly reduced the Cd content in the above-ground parts of lettuce by 74.76%, and had the least impact on lettuce biomass. It can be inferred that RSD is an ecologically effective method for the remediation of Cd pollution in facility soil by improving soil characteristics and altering microbial community composition to reduce Cd activity. However, further in-depth research is needed to optimize the types and amounts of organic materials applied.

Natural biocide-assisted ultrasonic disinfection of wastewater effluent following a response surface methodology approach

The increasing prevalence of multidrug-resistant (MDR) bacteria in wastewater poses a significant threat to public health and the environment, necessitating more effective and sustainable disinfection methods. Ozonation and chlorination frequently fall short of eliminating these bacteria and can create toxic byproducts. This study introduces a novel disinfection strategy that combines ultrasonication with tea tree oil to target MDR bacteria in residential wastewater treatment systems, aiming to provide an eco-friendly, efficient, and scalable solution. The method harnesses tea tree oil's natural biocidal properties alongside the physical effects of ultrasonication, particularly acoustic cavitation, to enhance bacterial inactivation. Temperature, biocide dosage, and ultrasonication power were the three main factors that were optimized using response surface methodology. The system achieved a 2.2–2.4 log CFU/mL reduction of total bacteria in secondary effluent within 30 min and complete disinfection of modified effluent inoculated with high-strength MDR bacteria (6-log CFU/mL) in 50 min. Optimal conditions were 698.4 Watt power, 1.234 µl/mL tea tree oil, and 20.64 °C. Nucleic acid release and respiratory chain dehydrogenase inhibition indicated bacterial cell membrane rupture. Regrowth tests showed long-term effectiveness, with no bacterial colonies after three days. Using a natural biocide, the hybrid technique reduces operational costs and time, thus having commercial and environmental benefits. The capacity to remove MDR bacteria makes it an attractive contender for large-scale wastewater treatment.

Efficient Surface Sterilant for Establishment of Dendrobium in vitro Culture

Background: Most orchid species in the Dendrobium genus are epiphytic. Dendrobium orchid (Dendrobium nobile L.) var. Sonia is a non-woody epiphytic orchid that bears a beautiful purple-coloured flower and grows in soilless medium. Dendrobium can be propagated vegetatively through divisions or Keikis. But this propagation method is extremely slow. Micropropagation is most suitable method for multiplication of dendrobium orchids. Surface sterilization is an important step in the preparation of vigorous and viable explants in micropropagation. Most of the surface contaminants can be abolished by surface sterilization with a suitable sterilizing agent. The aim of the investigation is to present an effective disinfection method for the aseptic culture of Dendrobium var. Sonia by using nodal segments. Methods: In the present investigation, two sterilant were employed namely mercuric chloride (HgCl2) and sodium hypochlorite (NaOCl) at different concentrations and durations. A total of nine combinations were tried for treating nodal explants in this investigation during 2022-2023. Explants were surface sterilized with 70% ethanol for 5 minutes followed by 3 to 4 washes with sterile distilled water. Thereafter, the explants were subjected to different surface sterilization treatments to establish contamination free cultures. Result: The study revealed that among the 9 treatments, minimum contamination (30.40%) was recorded in 0.1% HgCl2 for 10 minutes which helps in the maximum establishment of healthy culture (69.60%). Whereas, the lowest result for establishment was found in autoclaved distilled water with maximum contamination (100%). Maximum explant mortality (20.80%) due to sterilant was observed in NaOCl (2%) for 20 minutes.

Efficacy of slow sand filtration enriched with Trichoderma atroviride in the control of Rhizoctonia solani in soilless culture

Soilless cultivation is increasingly common, but the nutrient-rich drainage from substrate cultivation is often discarded. However, drainage can be safely reused if previously disinfected. Slow sand filtration (SSF) is a low-cost, ecological, and effective method for water disinfection, primarily through biological control. Enhancing SSF with antagonistic microorganisms is not well-studied. Additionally, SSF has not been tested to control Rhizoctonia solani, a phytopathogen that can be spread by irrigation water. Therefore, the objective of his work was to test the efficacy of a slow sand filter improved through the inoculation of the antagonistic fungus Trichoderma atroviride, evaluating its suppression capacity against Rhizoctonia solani spread by the irrigation water in a closed substrate cultivation of cucumber (Cucumis sativus). Five experiments were conducted, testing the presence and absence of a sand filter, T. atroviride, and R. solani in each trial. Median disease severity was expressed on a scale of 1–5. The improved SSF increased disease control percentage by 49% compared to SSF alone and by 86% compared to no disease control method. In some experiments, SSF with T. atroviride totally controlled R. solani. The results confirm that biologically enhanced SSF with T. atroviride can effectively disinfect drainage in closed soilless cultivation systems infected with R. solani.

Assessment of immunopathological responses of a novel non-chemical biocide in C57BL/6 for safe disinfection usage

BackgroundWater electrospray technology has been developed and extensively studied for its physical properties and potential application as a non-chemical biocide against airborne pathogens. However, there are still concerns regarding the safety and potential toxicity of inhaling water electrospray (WE) particles. To address these potential hazards and offer insights into the impact of WE on humans, we analyzed the immunopathological response to WE by employing an intranasal challenge C57BL/6 mouse model. This analysis aimed to compare the effects of WE with those of sodium hypochlorite (SH), a well-known biocidal agent.ResultsThe study findings suggest that the WE did not trigger any pathological immune reactions in the intranasal-challenged C57BL/6 mouse model. Mice challenged with WE did not experience body weight loss, and there was no increase in inflammatory cytokine production compared to SH-treated mice. Histopathological analysis revealed that WE did not cause any damage to the lung tissue. In contrast, mice treated with SH exhibited significant lung tissue damage, characterized by the infiltration of neutrophils and eosinophils. Transcriptomic analysis of lung tissue further confirmed the absence of a pathological immune response in mice treated with WE compared to those treated with SH. Upon intranasal challenge with WE, the C57BL/6 mouse model did not show any evidence of immunopathological damage.ConclusionsThe results of this study suggest that WE is a safe technology for disinfecting airborne pathogens. It demonstrated little to no effect on immune system activation and pathological outcomes in the intranasal challenge C57BL/6 mouse model. These findings not only support the potential use of WE as an effective and safe method for air disinfection but also highlight the value of the intranasal challenge of the C57BL/6 mouse model in providing significant immunopathological insights for assessing the inhalation of novel materials for potential use.

Comparative Evaluation of Disinfection Protocols for Dental Impressions in Prosthodontics.

In prosthodontics, dental impressions are essential for creating precise dental restorations. However, these impressions are susceptible to microbial contamination, which can pose a risk of infection to patients. Consequently, effective disinfection methods are crucial to prevent postoperative infections. This study aims to evaluate the effectiveness of various disinfection techniques for dental impressions used in prosthodontics. A total of 148 poured dental impressions were randomized into three disinfection groups: immersed in 0.5% sodium hypochlorite, 2% glutaraldehyde, or 0.2% chlorhexidine solution. The bacterial contamination was evaluated by direct colony-forming unit (CFU) counting, while the dimensional accuracy and surface detail duplication of each resin sample were determined as physical properties. Data were analyzed using SPSSversion 23.0 (IBM Corp., Armonk, NY). Either analysis of variance (ANOVA) with the option for post-hoc or non-parametric tests was used to investigate and compare the efficacy of the better disinfection protocols where the p-value was considered significant if less than 0.05. Glutaraldehyde showed the lowest mean CFU count (2.5 log10 CFUs), followed by sodium hypochlorite (3.2 log10 CFUs) and chlorhexidine (3.5 log10 CFUs). All disinfection protocols were able to significantly reduce microbial contamination when compared with the control group (p < 0.05). The results of the physical property assessment demonstrated acceptable dimensional accuracy in all tested protocols, with slight differences recorded between them regarding the reproduction of surface detail. More specifically, the mean dimensional deviation was in the range between 0.02 and 0.04 mm, while scores for surface detail reproduction ranged from 2 to 4. The ANOVA results revealed significant differences in microbial contamination levels (F(2, 145) = 5.72, p = 0.007) and dimensional accuracy (F(2, 145) = 3.45, p = 0.032) between the various disinfection protocols. This study enlightens the effective sterilization protocol to be adopted in prosthodontics for dental impressions. Glutaraldehyde was most effective in microbial reduction, while sodium hypochlorite and chlorhexidine were equally effective. Therefore, clinicians must be vigilant in assessing the type of microbial flora that can be encountered during prosthodontic procedures while choosing disinfection protocols for patient safety and quality of impressions.

Disinfection Methods of Pruning Scissor for Preventing Transmission of Fire Blight

Pathogens of fire blight can survive for a long time on pruning tools, etc., and fire blight can be spread through agricultural implements. In particular, in Korea, pruning is frequently performed to remove flowers, immature fruits, and succulent shoots, and this farm work is known to be a major factor of the spread of fire blight. Therefore, in this study, in order to completely sterilize pathogens on pruning shears, we verified the disinfection effect of disinfectants distributed domestically and used them to identify an effective disinfection method. When disinfecting by immersion after inoculating Erwinia amylovora TS3128 on the scissor blade, 70% ethanol and 1% and 0.2% sodium hypochlorite sterilized immediately 10 sec after immersion, while 30% chlorine dioxide showed little disinfection effect. When disinfecting by spraying, 70% ethanol sterilized bacteria 1 sec after spraying, but 1% and 0.2% sodium hypochlorite disinfected bacteria after 10 and 60 sec, respectively. After cutting the naturally disease occurring branches five and 100 times, the bacteria were not hardly sterilized in immersion treatment in 70% ethanol for 30 sec but perfectly disinfected over 60 sec. Considering these results, pruning shears should be disinfected by frequently immersing them in 70% ethanol for at least 60 sec during pruning work in the field.

Disinfection of sink drains to reduce a source of three opportunistic pathogens, during Serratia marcescens clusters in a neonatal intensive care unit.

Evaluate the effects of five disinfection methods on bacterial concentrations in hospital sink drains, focusing on three opportunistic pathogens (OPs): Serratia marcescens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. Over two years, three sampling campaigns were conducted in a neonatal intensive care unit (NICU). Samples from 19 sink drains were taken at three time points: before, during, and after disinfection. Bacterial concentration was measured using culture-based and flow cytometry methods. High-throughput short sequence typing was performed to identify the three OPs and assess S. marcescens persistence after disinfection at the genotypic level. This study was conducted in a pediatric hospitals NICU in Montréal, Canada, which is divided in an intensive and intermediate care side, with individual rooms equipped with a sink. Five treatments were compared: self-disinfecting drains, chlorine disinfection, boiling water disinfection, hot tap water flushing, and steam disinfection. This study highlights significant differences in the effectiveness of disinfection methods. Chlorine treatment proved ineffective in reducing bacterial concentration, including the three OPs. In contrast, all other drain interventions resulted in an immediate reduction in culturable bacteria (4-8 log) and intact cells (2-3 log). Thermal methods, particularly boiling water and steam treatments, exhibited superior effectiveness in reducing bacterial loads, including OPs. However, in drains with well-established bacterial biofilms, clonal strains of S. marcescens recolonized the drains after heat treatments. Our study supports thermal disinfection (>80°C) for pathogen reduction in drains but highlights the need for additional trials and the implementation of specific measures to limit biofilm formation.

Effective of different industrial disinfection in subzero cold-chain environment

Effective disinfection methods are crucial in the cold chain transportation process of food due to the specificity of temperature and the diversity of contaminated flora. The objective of this study was to investigate the sanitizing effect of different disinfectants on various fungi at – 20 °C to achieve accurate disinfection of diverse bacterial populations. Peracetic acid, hydrogen peroxide, and potassium bisulfate were selected as low-temperature disinfectants and were combined with antifreeze. The sanitizing effect of these cryogenic disinfectants on pathogens such as Bacillus subtilis black variant spores (ATCC9372), Staphylococcus aureus (ATCC 6538), Candida albicans (ATCC 10231), Escherichia coli (8099), and poliovirus (PV-1) was sequentially verified by bactericidal and virus inactivation experiments. After a specified time of disinfection, a neutralizing agent was used to halt the sanitizing process. The study demonstrates that different disinfectants exhibit selective effects during the low-temperature disinfection process. Peracetic acid, hydrogen peroxide, and potassium monopersulfate are suitable for the low-temperature environmental disinfection of bacterial propagules, viruses, and fungal contaminants. However, for microorganisms with strong resistance to spores, a low-temperature disinfectant based on peracetic acid should be chosen for effective disinfection treatment. Our results provide a valuable reference for selecting appropriate disinfectants to sanitize various potential pathogens in the future.

Triton X-100 enhanced antibacterial effect of photodynamic therapy against Enterococcus faecalis infection: an in vitro study

Photodynamic therapy (PDT) is an effective method for bacterial infection control in root canals of teeth with a broad-spectrum antibacterial activity. However, its application in root canal treatment is limited due to its inefficiency under hypoxic conditions and dentin staining. Triton X-100 (TX) shows great potential in enhancing the efficiency of antimicrobial agents through improving bacterial membrane permeability. The present study employed a combination of toluidine blue O (TB)-mediated PDT with TX to target the Enterococcus faecalis (E. faecalis), a bacterium with strong resistance to various antibacterial agents and mostly detected in infected root canals. PDT combined with TX showed enhanced antibacterial efficiency against both planktonic cells and biofilms of E. faecalis. At the same time, TX enhanced the antibacterial effect in dentinal tubules and reduced the incubation time. Mechanism studies revealed that TX improved reactive oxygen species (ROS) production through increasing the proportion of TB monomers. Additionally, increased membrane permeability and wettability were also observed. The findings demonstrated the PDT combined with TX could be used as a highly effective method for the root canal disinfection of teeth.

Why is HSO5− so effective against bacteria? Insights into the mechanisms of Escherichia coli disinfection by unactivated peroxymonosulfate

This study examined the antimicrobial efficacy of peroxymonosulfate (PMS) against bacteria, using Escherichia coli (E. coli) as a model organism. Our investigation delineates the complex mechanisms exerted by unactivated PMS. Thus, an initial redox reaction between PMS and the target biomolecules of bacteria generates SO4•− as the pivotal reactive species for bacterial inactivation; to a lesser extent, •OH, 1O2, or O2•− may also participate. Damage generated during oxidation was identified using an array of biochemical techniques. Specifically, redox processes are promoted by PMS and SO4•− targets and disrupt various components of bacterial cells, predominantly causing extracellular damage as well as intracellular lesions. Among these, external events are the key to cell death. Finally, by employing gene knockout mutants, we uncovered the role of specific gene responses in the intracellular damage induced by radical pathways. The findings of this study not only expand the understanding of PMS-mediated bacterial inactivation but also explain the ten-fold higher effectiveness of PMS than that reported for H2O2. Hence, we provide clear evidence that unactivated PMS solutions generate SO4•− in the presence of bacteria, and consequently, should be considered an effective disinfection method.

Development of a standard evaluation method for microbial UV sensitivity using light-emitting diodes

Ultraviolet (UV) light is an effective disinfection method. In particular, UV light-emitting diodes (UV-LEDs) are expected to have many applications as light sources owing to their compact form factor and wide range of choices of wavelengths. However, the UV sensitivity of microorganisms for each UV wavelength has not been evaluated comprehensively because standard experimental conditions based on LED characteristics have not been established. Therefore, it is necessary to establish a standard evaluation method based on LED characteristics. Here, we developed a new UV-LED device based on strictly controlled irradiation conditions using LEDs for each wavelength (250–365 nm), checked the validity of the device characteristics and evaluated the UV sensitivity of Escherichia coli using this new evaluation method. For this new device, we considered accurate irradiance, accurate spectra, irradiance uniformity, accurate dose, beam angle, surrounding material reflections, and sample condition. From our results, the following UV irradiation conditions were established as standard: 1 mW/cm2 irradiance, bacterial solution with absorbance value of A600 = 0.5 diluted 10 times solution, solution volume of 1 mL, working distance (WD) of 100 mm. In order to compare the effects of irradiation under uniform conditions on inactivation of microorganisms, we assessed inactivation effect of E. coli by LED irradiation at each wavelength using the U280 LED as a standard wavelength. The inactivation effect for U280 LED irradiation was −0.95 ± 0.21 log at a dose of 4 mJ/cm2. Under this condition of dose, our results showed a high wavelength dependence of the inactivation effect at each UV wavelength peaking at 267 nm. Our study showed that this irradiation system was validated for the standard UV irradiation system and could be contributed to the establishment of food and water hygiene control methods and the development of equipment for the prevention of infectious diseases.

Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: An in vitro study – Part 2

Statement of problemDisinfection is an important factor in preserving facial prostheses and maintaining tissue health. However, whether disinfection with ultraviolet C is an effective disinfection method is unclear. PurposeThe purpose of this in vitro study was to evaluate the effectiveness of irradiation with different exposure durations of an ultraviolet-C light-emitting diode in the disinfection of the silicone (A-588–1; Factor II) used in facial prostheses. Material and methodsA total of 216 specimens were prepared, contaminated by multispecies biofilm, and divided into 9 groups (n=24) for different treatments: chlorhexidine 0.12% (G CHG), ultraviolet-C light-emitting diode for 5 minutes (G UVC5), ultraviolet-C light-emitting diode for 10 minutes (G UVC10), ultraviolet-C light-emitting diode for 20 minutes (G UVC20), their respective untreated controls (Gcontrol CHG, Gcontrol UVC5, Gcontrol UVC10, Gcontrol UVC20), and dimethyl sulfoxide (G DMSO) as the negative control. Cell viability was measured by using the methyl tetrazolium salt (MTT) method. Two statistical analyses were performed. First, a 2×3 ANOVA was carried out to compare the control groups (Gcontrol UVC5, Gcontrol UVC10, and Gcontrol UVC20) and the experimental groups of UV-C LED light with different exposure durations (G UVC5, G UVC10, and G UVC20). The second analysis was performed using generalized linear models to compare the optical density of the groups (G UVC5, G UVC10, G UVC20, G CHG, and G DMSO). ResultsCell viability results demonstrated a microbial reduction after exposure to the ultraviolet-C light-emitting diode for 20 minutes (G UVC20) compared with untreated controls (P<.05). The 5- and 10-minute exposures were statistically similar to their respective control groups (P>.05). The 20 minutes exposure had the lowest average optical density value, being statistically different from the 5-minute exposure (P<.05). A 20-minute exposure to the ultraviolet-C light-emitting diode (G UVC20) was similarly effective when compared with the standard disinfection treatment (G CHG) and dimethyl sulfoxide (G DMSO) (P>.05). ConclusionsIrradiation with an ultraviolet-C light-emitting diode for 20 minutes decreased the in vitro microbial cell viability on the medical silicone used in facial prostheses.

Microplastics and volatile organic compounds released from face masks after disinfection: Layers and materials differences

Effective disinfection methods are critical for ensuring the reusability of masks, yet these methods may inadvertently introduce health concerns associated with microplastics (MPs) and volatile organic compounds (VOCs). This study investigated the impact of ultraviolet germicidal irradiation (UVGI) and sodium hypochlorite (NaClO) bleaching on mask filter layers composed of four distinct materials. Our results revealed that UVGI induced more pronounced damage compared to bleaching, leading to the significant release of both MPs and VOCs. After UVGI treatment at conventional disinfection doses, meltblown (MB) fabrics released MPs reaching 864 ± 182 μg/g (92 ± 19 particles/g). For all filter layers, the quantity of released MPs followed the order: MB > HDPE>PU ≈ NW. These MPs were identified as degraded debris from the mask filter layers. The specific VOCs generated varied depending on the material composition. Non-woven (NW) and MB fabrics, both comprised of polypropylene, predominantly produced various branched aliphatic hydrocarbons and their derivative oxides. The cotton-like fabric, composed of high-density polyethylene, primarily emitted different linear aliphatic hydrocarbons and oxygenates. In contrast, the polyurethane filter layer of reusable masks released aromatic compounds, nitrogenous compounds, and their oxidation products. The formation of VOCs was primarily attributed to bond breakage and oxidative damage to the filter structure resulting from the disinfection process. In summary, as UVGI induced higher yields of MPs and VOCs compared to bleaching, the latter would be a safer option for mask disinfection.

Disinfection Efficacy of Electrohydraulic Discharge Plasma against Xanthomonas campestris pv campestris: A Sustainable Seed Treatment Approach.

The prevalence of plant diseases caused by pathogens such as Xanthomonas campestris pv campestris (Xcc) poses a significant challenge to sustainable agriculture, necessitating the development of effective and eco-friendly disinfection methods. In this study, we investigated the efficacy of electrohydraulic discharge plasma (EHDP) as a promising alternative for disinfection against Xcc, a pathogen responsible for black rot in cruciferous vegetables. Unlike conventional gas-phase plasma, EHDP introduces two pivotal components: gas-liquid interface plasma (GLIP) and its consequential byproduct, plasma-activated water (PAW). While GLIP enables dual-phase production of reactive oxygen and nitrogen species (RONS), PAW is a reservoir of liquid-phase long-lived RONS, thereby enhancing its bactericidal efficacy. In our evaluations, we tested EHDP-induced GLIP and EHDP-induced PAW against Xcc cells in both in vitro (Xcc suspension) and in vivo (Xcc-inoculated cabbage seeds) settings, achieving noteworthy results. Within 15 min, these methods eliminated ∼98% of the Xcc cells in suspension. For in vivo assessments, nontreated seeds exhibited an infection rate of 98%. In contrast, both EHDP treatments showed a significant reduction, with ∼60% fewer seeds infected while maintaining ∼90% germination rate. In addition, the liquid-phase RONS in EHDP-PAW may enhance seed vigor with a faster germination rate within the initial 5 days. Remarkably, around 90% of EHDP-PAW-treated seeds yielded healthy seedlings, indicating dual benefits in bacterial suppression and seed growth stimulation. In contrast, the percentage of healthy seedlings from nontreated, Xcc-inoculated seeds was approximately 70%. Our research demonstrates the feasibility of using eco-friendly EHDP in the seed disinfection process.

Effect of Disinfection Method and Testing Methodology on the Performance of a Breath-Enhanced Jet Nebulizer.

National guidelines for cystic fibrosis recommend cleaning and disinfecting nebulizers after each use. We tested two groups of five reusable breath-enhanced nebulizers after 0, 5, 10, 15, 20, 30, 60, 90, 120, 150, and 180 sterilization (baby bottle sterilizer) or cleaning cycles. The nebulizers were operated for 7 min (6 L/min) after loading albuterol (2.5 mg/3 mL), and they were evaluated with and without breathing simulation after cleaning/sterilization (0-180 and 0-60 cycles, respectively). Over the course of 180 cleaning/sterilization cycles, the mean (SD) solution output was 1.33 mL (0.12 mL)/1.29 mL (0.08 mL); the nebulizer mass remaining in the nebulizer was 61.5% (5.2%)/63% (4%); sputtering time was 4.7 min (0.8 min)/4.8 s (0.6 min); inspiratory filter was 19% (3%)/18.5% (2.4%); expiratory filter was 6.7% (1.1%)/6.7% (0.8%); and difference in drug output calculated using the solution output and nebulizer mass was 6.8% (4%)/5.2% (2.9%). Thermal disinfection with a baby-bottle sterilizer did not alter the performance of a reusable breath-enhanced nebulizer. The nebulizer test performed without breathing simulation underestimated its performance. The calculation of the drug output based on the solution output resulted in its overestimation.

Enhancing the effectiveness of bioaerosol disinfection in indoor environments by optimizing far-UVC lamp locations based on Markov chain model

Far-ultraviolet C (far-UVC) light is an effective and safe disinfection method for bioaerosol control in occupied indoor environments. The installation location of a far-UVC lamp strongly influences the spatial distribution of far-UVC irradiance, and thus the effectiveness of bioaerosol disinfection. To assist the design process, this study developed a fast prediction approach based on the Markov chain model for optimizing the installation locations of far-UVC lamps in order to enhance the disinfection effectiveness for indoor bioaerosol control. Experiments were conducted in an environmental chamber to validate the proposed simulation-based optimization approach. The results show that the proposed method can correctly predict the disinfection efficiency when compared with experimental data, and optimizing the installation location of the far-UVC lamp increased the disinfection efficiency by 54 % compared with the worst location. As an application, the validated method was then used to design the installation location of a far-UVC lamp in a real conference room. The results show that installing the far-UVC lamp in the optimal location can increase the disinfection efficiency by 48 % compared with the worst installation location. Therefore, optimizing the far-UVC lamp location using the proposed Markov chain model can enhance the effectiveness of bioaerosol disinfection in indoor environments.

Health care functions of ozone sterilizer

People’s Daily life and physical health are often plagued by viruses and bacteria. The novel coronavirus epidemic several years ago has seriously affected the global economy and social life. In addition to vaccination, ecologically safe and long-term and effective disinfection methods are very necessary. Ozone is an efficient and broad-spectrum bactericidal disinfectant, and the trace level of ozone in the atmosphere can make many viruses and bacteria lose their biochemical activity and infectivity. Nature produces trace amounts of ozone in the air through lightning to achieve the purpose of purifying the ecological environment. The product of ozone decomposition is oxygen, without secondary pollution. Ozone sterilizer has been widely used in epidemic prevention and control in intensive breeding farms and has achieved remarkable effects. If the concentration and action time can be accurately controlled, then ozone can effectively eliminate pathogens without harming normal cells in the human body. Therefore, the use of mini household ozone disinfectors for personal epidemic prevention and health care is a topic worth serious research. Shanghai Finerule Company has done a lot of tentative work in this respect and has achieved some good results.

Investigating the Effect of Different Disinfection Methods on the Efficiency, Pressure Drop and Quality Factor of Medical Masks

Background and Objective: This study was conducted with the aim of determining the effect of different disinfection methods on the efficiency, pressure drop, and quality of medical masks used by medical staff. The filtration efficiency of medical masks was also investigated in the present study. Materials and Methods: In the present study, four models of medical masks used by the treatment staff were selected. The masks were then disinfected with the disinfection methods recommended by the disease control and prevention centers, including heat methods, autoclaves, ultraviolet rays, immersion in 70% alcohol, and immersion in sodium hypochlorite. Finally, the effect of each disinfection method on the efficiency, pressure drop, and quality of the masks was checked using the test system. Results: Based on the results obtained from the study, disinfecting masks using thermal methods, autoclaving, ultraviolet radiation, immersion in sodium hypochlorite, and immersion in 70% alcohol caused changes in efficiency by 5.58%, 9.83%, 8.15%, 13.34%, and 20.38%, respectively. Additionally, changes in pressure drop were observed at rates of 12.9, 7, 6.92, 183.75, and 16.13 Pa, respectively. Moreover, the quality factor of masks improved after disinfection using thermal methods and autoclaving, in contrast to other methods. Furthermore, the assessment of filtration efficiency indicated that three out of four types of masks examined had efficiencies lower than 85%. Conclusion: Disinfection of medical masks using the heat method was chosen as the best disinfection method due to the least change in efficiency, a slight increase in pressure drop, and availability, and the 70% alcohol immersion method was chosen as the weakest disinfection method due to the decrease in efficiency, increase in pressure drop, and destruction of the mask's structure.

Microbiological analysis concerning the antibacterial effect of atomized Ionless® hypochlorous acid water in a nursery school environment

IntroductionIn daycare centers, infants come in close contact with each other, and contact, droplet, and mouth-to-mouth infections may occur owing to sharing of toys. Additional effective disinfection methods should be considered aside from wiping with disinfectants—including alcohol or sodium hypochlorite solution—for environmental disinfection of daycare centers. We aimed to examine the usefulness of hypochlorous acid water atomization in the effective disinfection of the classroom environment and toys at a nursery school. MethodsEnvironmental cultures of the nursery and toys were prepared to evaluate the species and bacterial load and to assess the contaminated areas. Staphylococcus aureus petri dishes were placed at high-frequency contact sites, and hypochlorous acid water was atomized to achieve a 0.03-ppm atmospheric chlorine concentration. After the atomization, the amount of S. aureus bacteria on the Petri dish and the changes in bacterial count isolated from the environment and toys were evaluated. ResultsHypochlorous acid water atomization was performed for 5 h to avoid condensation. After a 3-h atomization, ≥99.99% of S. aureus was eliminated on petri dishes; furthermore, a significant disinfection effect was observed on environmental bacteria at least 1 h after atomization. For rubber and textile toys, the significant disinfection effect was observed 1 h after atomization, and for plastic toys, the effect was observed 3 h after atomization. ConclusionsHypochlorous acid water atomization is a useful strategy to disinfect nursery school classrooms.