An automated room disinfection system using ozone is highly active against surrogates for SARS-CoV-2

Hygiene requirements for cleaning and disinfection of surfaces: recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute

This recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) addresses not only hospitals, but also outpatient health care facilities and compiles current evidence. The following criteria are the basis for the indications for cleaning and disinfection: Infectious bioburden and tenacity of potential pathogens on surfaces and their transmission routes, influence of disinfecting surface cleaning on the rate of nosocomial infections, interruption of cross infections due to multidrug-resistant organisms, and outbreak control by disinfecting cleaning within bundles. The criteria for the selection of disinfectants are determined by the requirements for effectiveness, the efficacy spectrum, the compatibility for humans and the environment, as well as the risk potential for the development of tolerance and resistance. Detailed instructions on the organization and implementation of cleaning and disinfection measures, including structural and equipment requirements, serve as the basis for their implementation. Since the agents for surface disinfection and disinfecting surface cleaning have been classified as biocides in Europe since 2013, the regulatory consequences are explained. As possible addition to surface disinfection, probiotic cleaning, is pointed out. In an informative appendix (only in German), the pathogen characteristics for their acquisition of surfaces, such as tenacity, infectious dose and biofilm formation, and the toxicological and ecotoxicological characteristics of microbicidal agents as the basis for their selection are explained, and methods for the evaluation of the resulting quality of cleaning or disinfecting surface cleaning are presented.

Disinfection and sterilization: New technologies

BACKGROUND

Adherence to professional guidelines and/or manufacturer's instructions for use regarding proper disinfection and sterilization of medical devices is crucial to preventing cross transmission of pathogens between patients. Emerging pathogens (e.g., Candida auris) and complex medical devices provide new challenges.

METHODS

A search for published English articles on new disinfection and sterilization technologies was conducted by Google, Google scholar and PubMed.

RESULTS

Several new disinfection methods or products (e.g., electrostatic spraying, new sporicides, colorized disinfectants, "no touch" room decontamination, continuous room decontamination) and sterilization technologies (e.g., new sterilization technology for endoscopes) were identified.

CONCLUSIONS

These technologies should reduce patient risk.

Novel intrathoracic irrigation using ultrafine ozone bubbles in a rat empyema model

Dissolved ozone is generally used for sanitization, but it has not been used for thoracic cavity sanitization because of its short half-life (< 20 min) and possible toxicity. We developed a novel solution containing ultrafine ozone bubbles (ozone-UFB) with a fivefold longer half-life than non-UFB ozone. Using an in vitro model, Staphylococcus aureus colonies were counted after exposure to ozone-UFB or non-UFB ozone at the same ozone concentration (0.4 mg/L). The colony count was significantly lower in the ozone-UFB group than in the non-UFB ozone group (p = 0.034). The effect of repeated pleural irrigation using ozone-UFB and saline was compared in a rat empyema model of S. aureus infection. The bacterial count in the pleural effusion was decreased by at least fivefold following intrathoracic lavage with ozone-UFB (3 mg/L). To examine the safety of ozone-UFB for intrathoracic use, ozone-UFB with a higher ozone concentration (10 mg/L) was injected into the thoracic cavities of normal rats. The treatment did not result in any specific pleural damage or elevated serum interleukin-6 concentrations. The findings highlighted the efficacy and safety of ozone-UFB for intrathoracic sanitization, but further studies are needed to determine the optimal therapeutic ozone concentration with appropriate safety margins.

Ozone based inactivation and disinfection in the pandemic time and beyond: Taking forward what has been learned and best practice

The large-scale global COVID-19 has a profound impact on human society. Timely and effectively blocking the virus spread is the key to controlling the pandemic growth. Ozone-based inactivation and disinfection techniques have been shown to effectively kill SARS-CoV-2 in water, aerosols and on solid surface. However, the lack of an unified information and discussion on ozone-based inactivation and disinfection in current and previous pandemics and the absence of consensus on the main mechanisms by which ozone-based inactivation of pandemic causing viruses have hindered the possibility of establishing a common basis for identifying best practices in the utilization of ozone technology. This article reviews the research status of ozone (O3) disinfection on pandemic viruses (especially SARS-CoV-2). Taking sterilization kinetics as the starting point while followed by distinguishing the pandemic viruses by enveloped and non-enveloped viruses, this review focuses on analyzing the scope of application of the sterilization model and the influencing factors from the experimental studies and data induction. It is expected that the review could provide an useful reference for the safe and effective O3 utilization of SARS-CoV-2 inactivation in the post-pandemic era.

Ozone application in different industries: A review of recent developments

Ozone - a powerful antimicrobial agent, has been extensively applied for decontamination purposes in several industries (including food, water treatment, pharmaceuticals, textiles, healthcare, and the medical sectors). The advent of the COVID-19 pandemic has led to recent developments in the deployment of different ozone-based technologies for the decontamination of surfaces, materials and indoor environments. The pandemic has also highlighted the therapeutic potential of ozone for the treatment of COVID-19 patients, with astonishing results observed. The key objective of this review is to summarize recent advances in the utilisation of ozone for decontamination applications in the above-listed industries while emphasising the impact of key parameters affecting microbial reduction efficiency and ozone stability for prolonged action. We realise that aqueous ozonation has received higher research attention, compared to the gaseous application of ozone. This can be attributed to the fact that water treatment represents one of its earliest applications. Furthermore, the application of gaseous ozone for personal protective equipment (PPE) and medical device disinfection has not received a significant number of contributions compared to other applications. This presents a challenge for which the correct application of ozonation can mitigate. In this review, a critical discussion of these challenges is presented, as well as key knowledge gaps and open research problems/opportunities.

Infectivity of SARS-CoV-2 on Inanimate Surfaces: Don't Trust Ct Value

SARS-CoV-2 RNA is frequently identified in patient rooms and it was speculated that the viral load quantified by PCR might correlate with infectivity of surfaces. To evaluate Ct values for the prediction of infectivity, we investigated contaminated surfaces and Ct-value changes after disinfection. Viral RNA was detected on 37 of 143 investigated surfaces of an ICU. However, virus isolation failed for surfaces with a high viral RNA load. Also, SARS-CoV-2 could not be cultivated from surfaces artificially contaminated with patient specimens. In order to evaluate the significance of Ct values more precisely, we used surrogate enveloped bacteriophage Φ6. A strong reduction in Φ6 was achieved by three different disinfection methods. Despite a strong reduction in viability almost no change in the Ct values was observed for UV-C and alcoholic surface disinfectant. Disinfection using ozone resulted in a lack of Φ6 recovery as well as a detectable shift in Ct values indicating strong degradation of the viral RNA. The observed lack of significant effects on the detectable viral RNA after effective disinfection suggest that quantitative PCR is not suitable for predicting the infectivity of SARS-CoV-2 on inanimate surfaces. Ct values should therefore not be considered as markers for infectivity in this context.

Ozone disinfection efficiency against airborne microorganisms in hospital environment: a case study

Even though ozone has shown its potential for air disinfection in hospital environment, its more frequent use has earned attention only with the COVID-19 pandemic due to its proven antimicrobial effect and low cost of production. The aim of this study was to determine its antimicrobial efficiency against the most common bacterial species in a real-life setting, that is, in the air of one postoperative room of the General Hospital Dr Ivo Pedišić (Sisak, Croatia). Air was sampled for aiborne bacteria before and after treatment with the ozone concentration of 15.71 mg/m3 for one hour. The most dominant Gram-positive bacteria of the genera Micrococcus, Staphylococcus, and Bacillus were reduced by 33 %, 58 %, and 61 %, respectively. The genus Micrococcus proved to be the most resistant. Considering our findings, we recommend longer air treatment with higher ozone concentrations in combination with mechanical cleaning and frequent ventilation.

Combined Biocidal Effect of Gaseous Ozone and Citric Acid on Acinetobacter baumannii Biofilm Formed on Ceramic Tiles and Polystyrene as a Novel Approach for Infection Prevention and Control

Acinetobacter baumannii is a prominent emerging pathogen responsible for a variety of hospital-acquired infections. It can contaminate inanimate surfaces and survive in harsh environmental conditions for prolonged periods of time in the form of biofilm. Biofilm is difficult to remove with only one method of disinfection, so combined disinfection methods and biocidal active substances are needed for biofilm eradication. Additionally, having in mind ecological demands, legislators are more prone using fewer toxic substances for disinfection that produce less solid waste and hazardous disinfection byproducts. Gaseous ozone and citric acid are natural biocidal compounds, and the purpose of this study was to determine their combined biocidal effects on A. baumannii biofilm formed on ceramics and polystyrene. Twenty-four-hour A. baumannii biofilm formed on ceramic tiles and polystyrene was exposed to different combinations of disinfection protocols with 25 ppm of gaseous ozone for 1 h exposure time and 15% citric acid for 10 min exposure. The total number of bacteria was counted afterwards and expressed as CFU/cm2. The determined disinfection protocols of A. baumannii biofilm with combined citric acid and gaseous ozone caused reduction of 2.8 to 5.89 log10 CFU (99.99% inhibition rate) of total viable bacteria for each method, with the citric acid–ozone–citric acid disinfection protocol being most successful in eradication of viable bacteria on both ceramics and polystyrene. In conclusion, gaseous ozone and citric acid showed good combined biocidal effects on A. baumannii biofilm and successfully reduced early A. baumannii biofilm from ceramic and polystyrene surfaces. The given combination of active substances can be a good option for eco-friendly disinfection of hospital inanimate surfaces from A. baumannii biofilm contamination with prior mechanical cleaning.

Ozone Eliminates SARS-CoV-2 from Difficult-to-Clean Office Supplies and Clinical Equipment

(1) Background: Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) continues to cause profound health, economic, and social problems worldwide. The management and disinfection of materials used daily in health centers and common working environments have prompted concerns about the control of coronavirus disease 2019 (COVID-19) infection risk. Ozone is a powerful oxidizing agent that has been widely used in disinfection processes for decades. The aim of this study was to assess the optimal conditions of ozone treatment for the elimination of heat-inactivated SARS-CoV-2 from office supplies (personal computer monitors, keyboards, and computer mice) and clinical equipment (continuous positive airway pressure tubes and personal protective equipment) that are difficult to clean. (2) Methods: The office supplies and clinical equipment were contaminated in an area of 1 cm² with 1 × 10⁴ viral units of a heat-inactivated SARS-CoV-2 strain, then treated with ozone using two different ozone devices: a specifically designed ozonation chamber (for low–medium ozone concentrations over large volumes) and a clinical ozone generator (for high ozone concentrations over small volumes). SARS-CoV-2 gene detection was carried out using quantitative real-time polymerase chain reaction (RT-qPCR). (3) Results: At high ozone concentrations over small surfaces, the ozone eliminated SARS-CoV-2 RNA in short time periods—i.e., 10 min (at 4000 ppm) or less. The optimum ozone concentration over large volumes was 90 ppm for 120 min in ambient conditions (24 °C and 60–75% relative humidity). (4) Conclusions: This study showed that the appropriate ozone concentration and exposure time eliminated heat-inactivated SARS-CoV-2 RNA from the surfaces of different widely used clinical and office supplies, decreasing their risk of transmission, and improving their reutilization. Ozone may provide an additional tool to control the spread of the COVID-19 pandemic.

Associations between the COVID-19 Pandemic and Hospital Infrastructure Adaptation and Planning—A Scoping Review

The SARS-CoV-2 pandemic has put unprecedented pressure on the hospital sector around the world. It has shown the importance of preparing and planning in the future for an outbreak that overwhelms every aspect of a hospital on a rapidly expanding scale. We conducted a scoping review to identify, map, and systemize existing knowledge about the relationships between COVID-19 and hospital infrastructure adaptation and capacity planning worldwide. We searched the Web of Science, Scopus, and PubMed and hand-searched gray papers published in English between December 2019 and December 2021. A total of 106 papers were included: 102 empirical studies and four technical reports. Empirical studies entailed five reviews, 40 studies focusing on hospital infrastructure adaptation and planning during the pandemics, and 57 studies on modeling the hospital capacity needed, measured mostly by the number of beds. The majority of studies were conducted in high-income countries and published within the first year of the pandemic. The strategies adopted by hospitals can be classified into short-term (repurposing medical and non-medical buildings, remote adjustments, and establishment of de novo structures) and long-term (architectural and engineering modifications, hospital networks, and digital approaches). More research is needed, focusing on specific strategies and the quality assessment of the evidence.

Evaluation of zone-disinfection effect of air-passable plasma filter in a novel chamber model

BACKGROUND

Disinfection of shared spaces has become essential to minimize the spread of various diseases. An efficient disinfection device that can simultaneously inactivate airborne bacteria and surface adhered bacteria in an enclosed space is required.

AIM

An air-passable plasma filter (APF) was developed and applied to a chamber model to evaluate the zone-disinfection effect.

METHODS

The 60 litre chamber consisted of a nebulizer, circulation fans, temperature and humidity monitors, an air sampling port with a sealed gate, airborne bacteria trapping media, and a built-in fan for evaluation. After spraying each bacterial strain (Escherichia coli, Staphylococcus epidermidis, and Mycobacterium smegmatis) as a bioaerosol, airborne and surface-attached bacteria were quantified simultaneously to evaluate the zone-disinfection effect of APF.

FINDINGS

The operation of APF in the 60 litre chamber showed a complete zone-disinfection effect for E. coli (10 min), S. epidermidis (10 min), and M. smegmatis (60 min) present in the air and on the walls at various locations. The time required to completely disinfect each of the airborne bacteria and surface-attached bacteria within the same space was different.

CONCLUSION

APF has the potential to exhibit significant germicidal effects on various microorganisms and can be an effective alternative for disinfection of enclosed spaces.

Potent Activity of a High Concentration of Chemical Ozone against Antibiotic-Resistant Bacteria

BACKGROUND

Health care-associated infections (HAIs) are a significant public health problem worldwide, favoring multidrug-resistant (MDR) microorganisms. The SARS-CoV-2 infection was negatively associated with the increase in antimicrobial resistance, and the ESKAPE group had the most significant impact on HAIs. The study evaluated the bactericidal effect of a high concentration of O3 gas on some reference and ESKAPE bacteria.

MATERIAL AND METHODS

Four standard strains and four clinical or environmental MDR strains were exposed to elevated ozone doses at different concentrations and times. Bacterial inactivation (growth and cultivability) was investigated using colony counts and resazurin as metabolic indicators. Scanning electron microscopy (SEM) was performed.

RESULTS

The culture exposure to a high level of O3 inhibited the growth of all bacterial strains tested with a statistically significant reduction in colony count compared to the control group. The cell viability of S. aureus (MRSA) (99.6%) and P. aeruginosa (XDR) (29.2%) was reduced considerably, and SEM showed damage to bacteria after O3 treatment Conclusion: The impact of HAIs can be easily dampened by the widespread use of ozone in ICUs. This product usually degrades into molecular oxygen and has a low toxicity compared to other sanitization products. However, high doses of ozone were able to interfere with the growth of all strains studied, evidencing that ozone-based decontamination approaches may represent the future of hospital cleaning methods.

Antiviral Characterization of Advanced Materials: Use of Bacteriophage Phi 6 as Surrogate of Enveloped Viruses Such as SARS-CoV-2

The bacteriophage phi 6 is a virus that belongs to a different Baltimore group than SARS-CoV-2 (group III instead of IV). However, it has a round-like shape and a lipid envelope like SARS-CoV-2, which render it very useful to be used as a surrogate of this infectious pathogen for biosafety reasons. Thus, recent antiviral studies have demonstrated that antiviral materials such as calcium alginate hydrogels, polyester-based fabrics coated with benzalkonium chloride (BAK), polyethylene terephthalate (PET) coated with BAK and polyester-based fabrics coated with cranberry extracts or solidified hand soap produce similar log reductions in viral titers of both types of enveloped viruses after similar viral contact times. Therefore, researchers with no access to biosafety level 3 facilities can perform antiviral tests of a broad range of biomaterials, composites, nanomaterials, nanocomposites, coatings and compounds against the bacteriophage phi 6 as a biosafe viral model of SARS-CoV-2. In fact, this bacteriophage has been used as a surrogate of SARS-CoV-2 to test a broad range of antiviral materials and compounds of different chemical natures (polymers, metals, alloys, ceramics, composites, etc.) and forms (films, coatings, nanomaterials, extracts, porous supports produced by additive manufacturing, etc.) during the current pandemic. Furthermore, this biosafe viral model has also been used as a surrogate of SARS-CoV-2 and other highly pathogenic enveloped viruses such as Ebola and influenza in a wide range of biotechnological applications.

Ozone as an alternative decontamination process for N95 facemask and biosafety gowns

COVID-19 pandemic created a global shortage of medical protective equipment. Here, we considered ozone (O₃) a disinfectant alternative due to its potent oxidative activity against biological macromolecules. The O₃ decontamination assays were done using SARS-CoV-2 obtained from patients to produce artificial contamination of N95 masks and biosecurity gowns. The quantification of SARS-CoV-2 was performed before and after exposing the samples to different ozone gas concentrations for times between 5 and 30 min. Viral loads as a function of the O₃ exposure time were estimated from the data obtained by the RT-PCR technique. The genetic material of the virus was no longer detected for any tested concentrations after 15 min of O₃ exposure, which means a disinfection Concentration-Time above 144 ppm min. Vibrational spectroscopies were used to follow the modifications of the polymeric fibers after the O₃ treatment. The results indicate that the N95 masks could be safely reused after decontamination with treatments of 15 min at the established O₃ doses for a maximum of 6 cycles.

Evaluation of Virucidal Efficacy of Cold Plasma on Bacteriophage Inside a Three-Layered Sterilization Chamber

Traditional disinfection methods against pathogens have numerous shortcomings, and inventive methods like cold plasma are required for virus inactivation. Here, an atmospheric pressure 13.56 MHz radio-frequency hollow cathode (RF–HC) cold plasma device has been used to build a cold plasma sterilization device, and its virucidal activity is assessed against P2 bacteriophage, a model surrogate for pathogenic viruses. The heart of this device contains a three-layered sterilization chamber which is a rectangular parallelopiped of 42 × 32 × 30 cm³. Optimization experiments were performed to make each corner of this chamber completely virus free after cold plasma treatment. This two-pronged study was conducted to establish the requirement of minimum vol. % H₂O₂ in minimum time for the complete elimination of phages inside this sterilization chamber even when plasma is not in the direct line of sight. In initial experiments, the effect of the direct plasma line of sight was seen as the top and bottom layers showing less phage killing as compared to the middle of the sterilization chamber. Complete sterilization of bacteriophage, in all the three layers inside the sterilization chamber, was achieved by plasma treatment with 6% H₂O₂ for 10 min in 80 watts of plasma operating power. It was also seen that 6% H₂O₂ mist alone is not sufficient to provide a high degree of sterilization, and normal water mist combined with cold plasma can provide a higher level of sterilization at each corner of the chamber.

Disinfection methods against SARS-CoV-2: a systematic review

Background

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus disease 2019, has caused millions of deaths worldwide. The virus is transmitted by inhalation of infectious particles suspended in the air, direct deposition on mucous membranes and indirect contact via contaminated surfaces. Disinfection methods that can halt such transmission are important in this pandemic and in future viral infections.

Aim

To highlight the efficacy of several disinfection methods against SARS-CoV-2 based on up-to-date evidence found in the literature.

Methods

Two databases were searched to identify studies that assessed disinfection methods used against SARS-CoV-2. In total, 1229 studies were identified and 60 of these were included in this review. Quality assessment was evaluated by the Office of Health Assessment and Translation's risk-of-bias tool.

Findings

Twenty-eight studies investigated disinfection methods on environmental surfaces, 16 studies investigated disinfection methods on biological surfaces, four studies investigated disinfection methods for airborne coronavirus, and 16 studies investigated methods used to recondition personal protective equipment (PPE).

Conclusions

Several household and hospital disinfection agents and ultraviolet-C (UV-C) irradiation were effective for inactivation of SARS-CoV-2 on environmental surfaces. Formulations containing povidone-iodine can provide virucidal action on the skin and mucous membranes. In the case of hand hygiene, typical soap bars and alcohols can inactivate SARS-CoV-2. Air filtration systems incorporated with materials that possess catalytic properties, UV-C devices and heating systems can reduce airborne viral particles effectively. The decontamination of PPE can be conducted safely by heat and ozone treatment.

High Intensity Violet Light (405 nm) Inactivates Coronaviruses in Phosphate Buffered Saline (PBS) and on Surfaces

It has been proven that visible light with a wavelength of about 405 nm exhibits an antimicrobial effect on bacteria and fungi if the irradiation doses are high enough. Hence, the question arises as to whether this violet light would also be suitable to inactivate SARS-CoV-2 coronaviruses. Therefore, a high-intensity light source was developed and applied to irradiate bovine coronaviruses (BCoV), which are employed as SARS-CoV-2 surrogates for safety reasons. Irradiation is performed in virus solutions diluted with phosphate buffered saline and on steel surfaces. Significant virus reduction by several log levels was observed both in the liquid and on the surface within half an hour with average log reduction doses of 57.5 and 96 J/cm2, respectively. Therefore, it can be concluded that 405 nm irradiation has an antiviral effect on coronaviruses, but special attention should be paid to the presence of photosensitizers in the virus environment in future experiments. Technically, visible violet radiation is therefore suitable for coronavirus reduction, but the required radiation doses are difficult to achieve rapidly.

Inappropriate use of ozone generators and their sales status: questionnaire survey of healthcare providers and investigation of online sales

Ozone generators have attracted attention as a result of the spread of severe acute respiratory syndrome coronavirus-2. In a questionnaire survey targeting healthcare facilities, 20 (91%) used ozone generators in patient areas, and five (23%) used them in indoor spaces occupied by people. A search for ozone generators on the Amazon Japan website revealed that 76% of products lacked information on ozone emission rate, coverage area and/or use time. These results suggest that ozone generators may be used inappropriately in hospitals and clinics, and have been sold to the general public without adequate information for assessing their safety and efficacy.

Virucidal efficacy of an ozone-generating system for automated room disinfection

Besides conventional prevention measures, no-touch technologies based on gaseous systems have been introduced in hospital hygiene for room disinfection. The whole-room disinfectant device Sterisafe Pro, which creates ozone as a biocidal agent, was tested for its virucidal efficacy based on Association Française de Normalisation Standard NF T 72-281:2014. All test virus titres were reduced after 150 and 300 min of decontamination, with mean reduction factors ranging from 2.63 (murine norovirus) to 3.94 (simian virus 40). These results will help to establish realistic conditions for virus inactivation, and assessment of the efficacy of ozone technology against non-enveloped and enveloped viruses.