Disinfecting Action of Gaseous Ozone on OXA-48-Producing Klebsiella pneumoniae Biofilm In Vitro

Multi-drug-resistant bacteria on household textiles: characteristics, transmission and low-temperature washing

The aim of this study was to analyse how the properties of reference-resistant bacterial strains and textiles affect the transmission of bacteria, the antibacterial potential of detergents and disinfectants and how this can be implemented in low-temperature washing. Bacterial cells were characterised by a hydrophobicity test, and textiles were characterised by roughness and surface energy. Transmission and suspension tests were then carried out, followed by an evaluation of the wash. The results show that cotton has the highest roughness, polyester is the most hydrophobic and MRSA (methicillin-resistant Staphylococcus aureus) is the most hydrophobic bacterium. It was observed that resistant bacteria can be transmitted to a considerable extent via household textiles. The suspension test showed that the 0.5% European Colourfastness Establishment (ECE) reference detergent did not achieve a sufficient reduction (>5 log colony forming units - CFU) for any of the strains tested, whereas the addition of 3% hydrogen peroxide or 4% quaternary ammonium silicone compound did so for all of them. Washing at 60 °C reduced the textile contamination sufficiently (>4 log CFU) for all strains tested, while the criteria for cross-contamination and wash water were not met (<1.1 CFU/mL). However, the addition of disinfectants to the detergent at 30 °C met all hygiene requirements with the complete elimination of all tested bacteria on all textiles. Washing home textiles contaminated with resistant bacteria at low temperatures was only possible if a disinfectant was added. Otherwise, textiles can be an important vehicle for the transmission of resistant bacteria in domestic facilities.

Effect of gaseous ozone treatment on cells and biofilm of dairy Bacillus spp. isolates

Bacillus spp. can produce biofilms and cause recurrent contamination in the food industry. The common clean-in-place (CIP) method is usually employed in sanitizing processing equipment. However, CIP is not always effective in removing biofilms. Ozone represents a promising "green" alternative to control biofilms. In this study, the effect of gaseous ozone (50 ppm) was evaluated in vitro against planktonic and sessile B. cereus and B. subtilis isolates collected from the dairy sector. Planktonic cells were enumerated by plate counts after 10 min, 1 h, and 6 h of ozone treatment. After a short-term (10 min) exposure, a slight reduction in microbial loads (0.66-2.27 ± 0.15 Log10 CFU/mL) was observed for B. cereus strains, whereas a more pronounced reduction (2.90-3.81 ± 0.12 Log10 CFU/mL) was noted in B. subtilis isolates. The microbial load further decreased after 1 h-treatments, around 1.5-3.46 ± 0.11 Log10 CFU/mL for B. cereus strains, and 4.0-5.6 ± 0.11 Log10 CFU/mL for B. subtilis isolates, until complete inactivation of bacterial cells after 6 h of exposure. Moreover, the effect of gaseous ozone treatment (50 ppm, 6 h) was evaluated for its ability to inhibit and eradicate biofilms formed on two common food-contact materials (polystyrene and stainless steel). Sessile B. subtilis cells were the more sensitive to the action of ozone, while a weak effect was highlighted on B. cereus isolates on both surface types. These results were further confirmed by scanning microscopy analysis. The number of cells in the biofilm state was also assessed, showing a not-complete correlation with a decrease in Biofilm Production Indices (BPIs). These findings highlighted the effectiveness of the sanitizing protocol using gaseous ozone in contrasting Bacillus free-living cells, but a not completely counteraction in biofilm formation (inhibition) or eradication of pre-formed biofilm. Thus, the application of ozone could be thought of not alone, but in combination with common sanitization practices to improve their effectiveness.

Comparison of different disinfection protocols against contamination of ceramic surfaces with Klebsiella pneumoniae biofilm

Environmental contamination with Klebsiella pneumoniae biofilm can be a source of healthcare-associated infections. Disinfection with various biocidal active substances is usually the method of choice to remove contamination with biofilm. In this study we tested 13 different disinfection protocols using gaseous ozone, citric acid, and three working concentrations of benzalkonium chloride-based professional disinfecting products on 24-hour-old biofilms formed by two K. pneumoniae strains on ceramic tiles. All tested protocols significantly reduced total bacterial counts compared to control, varying from a log10 CFU reduction factor of 1.4 to 5.6. Disinfection combining two or more biocidal active substances resulted in significantly better anti-biofilm efficacy than disinfection with single substances, and the most effective combination for both strains was that of citric acid, gaseous ozone, and benzalkonium chloride. This follow up study is limited to K. pneumoniae alone, and to overcome this limitation, future studies should include more bacterial species, both Gram-positive and Gramnegative, and more samples for us to find optimal disinfection protocols, applicable in real hospital settings.

The application of ozone within the food industry, mode of action, current and future applications, and regulatory compliance

The food industry faces numerous challenges today, with the prevention and reduction of microbial contamination being a critical focus. While traditional chemical-based methods are effective and widely used, rising energy costs, the development of microbial tolerances, and growing awareness of the ecological impact of chemical biocides have renewed interest in novel biocides. Ozone, in both its gaseous and aqueous forms, is recognized as a potent disinfectant against bacteria, viruses, and fungi due to its high oxidation potential. Our review highlights several studies on the applications of ozone within the food industry, including its use for surface and aerosol disinfection and its capacity to reduce viable Listeria monocytogenes, a pertinent foodborne pathogen harbouring environmental and biocide stress tolerances and biofilm former. We also explore the use of ozone in food treatment and preservation, specifically on blueberries, apples, carrots, cabbage, and cherry tomatoes. While ozone is an effective disinfectant, it is important to consider material incompatibility, and the risks associated with prolonged human exposure to high concentrations. Nevertheless, for certain applications, ozone proves to be an efficacious and valuable alternative or complementary method for microbial control. Compliance with the biocide products regulation will require ozone device manufacturers to produce proven efficacy and safety data in line with British standards based on European standards (BS EN), and researchers to propose adaptations to account for ozone's unique properties.

Physico-Chemical Investigation and Antimicrobial Efficacy of Ozonated Oils: The Case Study of Commercial Ozonated Olive and Sunflower Seed Refined Oils

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection of mutations that confer drug resistance to microbes. In this regard, recently, ozone has been raising interest for its unique biological properties when dissolved in natural oils. Ozonated oils have been reported to act in a non-specific way on microorganisms hindering the acquisition of advantageous mutations that result in resistance. Here, we focused on the antimicrobial effect of two commercial olive (OOO) and sunflower seeds (OSO) oils. Nuclear magnetic resonance spectroscopy and thermal analysis showed the change in the chemical composition of the oils after ozonation treatment. Different ozonated oil concentrations were then used to evaluate their antimicrobial profile against Candida albicans, Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli by agar diffusion and broth dilution methods. Cytotoxicity was also evaluated in keratinocytes and epithelial cells. Overall, our results revealed that both OOO and OSO showed a potent microbicidal effect, especially against C. albicans (IC50 = OOO: 0.3 mg/mL and OSO: 0.2 mg/mL) and E. faecalis (IC50 = OOO: 0.4 mg/mL and OSO: 2.8 mg/mL) albeit exerting a certain effect also against S. aureus and E. coli. Moreover, both OOO and OSO do not yield any relevant cytotoxic effect at the active concentrations in both cell lines. This indicates that the ozonated oils studied are not toxic for mammalian cells despite exerting a potent antimicrobial effect on specific microorganisms. Therefore, OOO and OSO may be considered to integrate standard therapies in the treatment of common infections, likely overcoming drug resistance issues.

Plasma-activated liquids for mitigating biofilms on food and food contact surfaces

Plasma-activated liquids (PALs) are emerging and promising alternatives to traditional decontamination technologies and have evolved as a new technology for applications in food, agriculture, and medicine. Contamination caused by foodborne pathogens and their biofilms has posed challenges and concerns to the food industry in terms of safety and quality. The nature of the food and the food processing environment are major factors that contribute to the growth of various microorganisms, followed by the biofilm characteristics that ensure their survival in severe environmental conditions and against traditional chemical disinfectants. PALs show an efficient impact against microorganisms and their biofilms, with various reactive species (short- and long-lived ones), physiochemical properties, and plasma processing factors playing a crucial role in mitigating biofilms. Moreover, there is potential to improve and optimize disinfection strategies using a combination of PALs with other technologies for the inactivation of biofilms. The overarching aim of this study is to build a better understanding of the parameters that govern the liquid chemistry generated in a liquid exposed to plasma and how these translate into biological effects on biofilms. This review provides a current understanding of PALs-mediated mechanisms of action on biofilms; however, the precise inactivation mechanism is still not clear and is an important part of the research. Implementation of PALs in the food industry could help overcome the disinfection hurdles and can enhance biofilm inactivation efficacy. Future perspectives in this field to expand existing state of the art to seek breakthroughs for scale-up and implementation of PALs technology in the food industry are also discussed.

Ozonated water in disinfection of hospital instrument table

Purpose

The walls, ceiling, and floor of a surgical environment, as well as the surfaces used in this place, must be submitted to a disinfection protocol to minimize nosocomial infections. Health regulations recommend two stages; the first is characterized by cleaning procedures, mainly using an enzymatic detergent, and the second is use of a disinfection agent. Ozone is a natural substance that has a relevant oxidative property for inactivating microorganisms and has emerged as an interesting agent in the hospital environment. Compared with conventional chemical products for disinfection, ozonated water has advantages such as a lack of storage control, disposal, and handling safety. The objective of this study was to use ozonated water as a disinfectant agent on a hospital metal surface, in comparison with 70% alcohol.

Methods

The degree of disinfection of the metal surface was quantitatively analyzed with use of an instrument by bioluminescence for a disinfection test.

Results

Qualitative terms indicated gram-positive cocci microorganisms and yeasts, suggesting that bacteria and fungi from the environment were identified. After the use of ozonated water as a disinfectant, the quantitative analysis indicated values below 100 RLU, showing evidence of a surface suitable for use in surgical procedures.

Conclusion

The use of ozonated water as a disinfectant agent for a metal surface in a hospital environment showed more effectiveness than 70% alcohol. Thus, ozonated water is a promising agent for disinfecting surfaces in surgical environments.

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.

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.