Inactivation Of Pathogenic Microorganisms Research Articles

Inactivation of Pathogenic Microorganisms by Deep-UV Light

Inactivation of Pathogenic Microorganisms by Deep-UV Light

Inactivation of pathogenic microorganisms under UV/O3 advanced disinfection system in mariculture water

Inactivation of pathogenic microorganisms under UV/O3 advanced disinfection system in mariculture water

Inactivation of pathogenic microorganisms in water by electron beam excitation multi-wavelength ultraviolet irradiation: Efficiency, influence factors and mechanism

Due to the limitations of traditional ultraviolet (UV) in microbial inactivation in water, it is necessary to explore a more suitable and efficient UV disinfection method. In this study, an electron beam excitation multi-wavelength ultraviolet (EBE-MW-UV) system was established and aims to analyze its differential microbial inactivation capabilities in comparison to single-wavelength UV-LEDs in waterborne applications. Furthermore, the inactivation mechanisms of this system on microorganisms were explored. The results showed that EBE-MW-UV had significantly higher inactivation effects on the Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Candida albicans in water compared to UV-LEDs (p＜0.05), and the inactivation effect of EBE-MW-UV on Escherichia coli and Pseudomonas aeruginosa at the same UV dose was 3.8 and 1.9 log higher than that of UV-LEDs, respectively, EBE-MW-UV exhibited better inactivation effects on Gram-negative bacteria. Further research found that, under the majority of irradiation doses, neither EBE-MW-UV nor UV-LEDs were significantly affected by the concentration of suspended solids (5 and 20mg/L) or humic acids (2 and 5mg/L) in the water. Mechanism analysis revealed that during the disinfection process of EBE-MW-UV, microbial DNA and proteins were initially damaged, which prevented the occurrence of dark repair and led to bacterial inactivation. In addition, UV irradiation led to the production of additional reactive oxygen species (ROS) inside the cells, increasing cell membrane permeability and exacerbating membrane damage. This was accompanied by a decrease in energy metabolism and depletion of ATP, ultimately resulting in microbial inactivation. Therefore, EBE-MW-UV demonstrated more effective disinfection than single-wavelength UV-LEDs, showing great potential. Our research gives new insights into the characteristics of multiple wavelength ultraviolet, and provides scientific basis for the selection of new light sources in the field of ultraviolet disinfection.

Analysis of a UV photocatalytic oxidation-based disinfection system for hydroxyl radicals, negative air ions generation and their impact on inactivation of pathogenic micro-organisms.

This work presents a large-scale surface disinfection system, which has a unique lantern arrangement of ultraviolet-C (UV-C) light (254nm) in conjunction with nanotechnology in a protective biosafety environment. Shadow regions are best dealt in this system by the generation of hydroxyl radicals (•OH) and negative air ions at sites where UV light cannot penetrate. More than 35 000 negative air ions/cm3 along with •OH were produced continuously in the disinfection chamber through the advanced photocatalytic oxidation process [UV-C + titanium dioxide (TiO2)]. The arrangement has been made to provide an optimized UV irradiation (∼2 mW/cm2) throughout the disinfection system. In order to distinguish between effects arising from (i) the action of UV dose alone and (ii) the action of UV dose along with •OH and negative air ions, E. coli and P. aeruginosa were chosen for bacterial testing and two interventions were made. The first intervention involved placing only UV lamps in the disinfection chamber to see the effect of only UV dose on bacterial inactivation efficiency. The second intervention involved placing the TiO2 nanoparticle coated aluminum plates along with UV lamps; this allows for the generation of negative air ions and •OH inside the disinfection chamber and enhanced bacterial inactivation efficiency. More than 95% bacterial inactivation efficiency has been reported in the case of UV-C + TiO2 compared to only 77% in UV only at the same time interval (90s).

Insights into the fate and properties of organic halamines during ultraviolet irradiation: Implications for drinking water safety

Organic halamines compounds present a significant threat to the safety of drinking water due to their potential toxicity and stability. While Ultraviolet (UV) disinfection is commonly used for water treatment, its specific effects on organic halamines and the underlying mechanisms remain poorly understood. In this study, we investigated eight amino acid-derived organic chlor- and bromamines as representative compounds. Our findings revealed that organic halamines have a slow hydrolysis rate (<10-3M-1s-1) and can persist in water for extended periods (30-2000min). However, their disinfection efficacy against Staphylococcus aureus and their ability to degrade micropollutants like carbamazepine were found to be limited. Interestingly, under UV irradiation, the N-X bonds in organic halamines were observed to break, leading to accelerated decomposition and the generation of abundant free radicals. These free radicals synergistically facilitated the removal of micropollutants and the inactivation of pathogenic microorganisms. It is worth noting that this transformation of organic halamines during UV disinfection resulted in a slight increase in the concentrations of nitrogenous disinfection byproducts. These findings shed light on the behavior and characteristics of organic halamines during UV disinfection processes, providing crucial insights for effectively managing drinking water quality impacted by these compounds. By understanding the implications of organic halamines, we can refine water treatment strategies and ensure the safety of drinking water supplies.

The simultaneous influence of ultraviolet rays and cold plasma on the physicochemical attributes and shelf life of dried pistachios during the storage period

AbstractThis investigation aimed to assess the simultaneous impact of ultraviolet (UV) and cold plasma (CP) on the quality and microbial attributes of dried pistachios during the storage period. Currently, novel nonthermal technologies exhibit high potential as a low‐cost, efficient, additive‐free, and nonpolluting strategies for fungi deactivation and mycotoxins degradation in foods. Over recent years, the combination of CP with other procedures, such as ultraviolet (UV) irradiation, ultrasound, ozone, and so forth, has been proposed and attracted lots of attention. For this purpose, in this study, the simultaneous effects of ultraviolet rays and cold plasma on dried pistachios artificially contaminated with aflatoxigenic fungi were assessed. The physicochemical attributes and surface morphology of pistachios were evaluated as well. The concentration of aflatoxin produced was investigated via high‐performance liquid chromatography. Artificially contaminated pistachios were treated with cold plasma at 80 W constant power level at both 10 and 15 min. Following the plasma treatment, pistachio samples were treated by ultraviolet rays at 354 nm wavelength and current intensity in 0.25 A at the same time. The results of this study revealed the fungal deactivation rate achieved by UV‐CP treatment was greater than the sum of the deactivation rates of distinct UV and CP treatments, as maximum reduction of Aspergillus oryzae count (3.7 CFU/g) observed after simultaneous UV‐CP treatment for 15 min (p &lt; 0.05). Moreover, no substantial modifications were detected in the investigation of pH and DPPH radical scavenging activity of samples treated with UV‐CP (p &gt; 0.05). The results of this study confirm the effectiveness of the simultaneous application of UV rays and CP in nuts to maintain quality and increase useful life, along with an alternative method for thermal treatments.Practical applicationsUsually, nonthermal procedures lead to their destruction by changing the chemical structure of mycotoxins. Ultraviolet (UV) radiation being a nonthermal technology, the benefits of its usage are various: the least loss of nutrients and sensorial quality of foods, no toxic residues, and low energy consumption compared with other thermal treatments normally applied for food decontamination. The latter is the main purpose of this technique due to its effectiveness in the inactivation of pathogenic microorganisms and spoilage. Besides this, Cold plasma (CP) technology has been displayed to overcome many of the insufficiency of regular decontamination strategies in the food industry, with slight damage to the quality of products and high efficiency. Although several physical procedures have shown acceptable results in the decontamination of fungi and degradation of mycotoxins in many foods, to date there are few published works on the effects of simultaneous application of UV radiation and CP on foods, particularly pistachios in is available. Hence, the intention of this investigation was to assess the effect of combination of UV radiation and CP on the physicochemical attributes and shelf life of dried pistachios during the storage period.

Inactivation of Pathogenic Microorganisms on Polymeric Materials through Ozonation

AbstractOzone‐based technologies have been evaluated to inactivate the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) on surfaces. However, the vast diversity of information makes it difficult to establish common ground for determining the best practices for using this technology. The objective of this work is to evaluate the success of N95 mask decontamination by ozonation, determining the specific parameters for process control. To quantify the effectiveness of the process, a disinfection protocol was initially developed based on two bacterial species (Escherichia coli and Staphylococcus pseudintermedius), followed by another disinfection assay using the murine hepatitis coronavirus (MHV‐3), in a laboratory‐scale prototype. Ozone is an effective candidate for use against SARS‐CoV‐2 or other viruses to disinfect personal protection equipment (PPE).

Synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater by electro-peroxone process.

Herein, a highly efficient electro-peroxone (E-peroxone) process with graphite felt as ozone diffusion electrode (ODE) was developed for the synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater. Under optimal conditions, the total organic carbon (TOC) removal rate of real hospital wastewater could reach 93.9%. Importantly, 126 pharmaceutical compounds (antibiotics, antivirals, analgesics, antiepileptics, hormones, and others) were determined in hospital wastewater by using ultra performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS). 110 pharmaceutical compounds could be efficiently degraded in E-peroxone system. Concurrently, the microbial community analysis through high-throughput sequencing showed that E-peroxone process exhibited an excellent disinfection effect in real hospital wastewater. Escherichia coli as a bacterial indicator could be completely inactivated in E-peroxone process·H2O2 and hydroxyl radical (OH) were found in E-peroxone system based on the results of chemical probe experiments and electron paramagnetic resonance (EPR) analysis. The in-situ generation of H2O2 from cathodic oxygen reduction in ODE can react with ozone to produce OH, and realize high efficiencies for the elimination of pharmaceutical and sterilization. This work established a green and effective way without extra addition of chemical reagents for high-efficiency treatment of real hospital wastewater.

Revisiting the protocol for determining submicromolar concentrations of ozone in the water treated by advanced oxidation processes.

Ozone is formed at submicromolar concentrations from photolysis of many oxyanions and oxidants in water and contributes importantly to the degradation of emerging contaminants and inactivation of pathogenic microorganisms in the natural and engineered aquatic systems. In this study, we identified and discussed the critical limitations of the commonly-used protocols using cinnamic acid (CNA) as a probe compound to determine the submicromolar-level ozone and proposed a modified protocol that overcomes those limitations. Our experimental investigation demonstrated that the radicals (e.g., HO•) formed from photolysis of oxyanions and oxidants, other than ozone, could also oxidize CNA and form benzaldehyde, resulting in the overestimation of ozone concentrations by using the commonly-used protocols. Moreover, the benzaldehyde formed from ozone-CNA reactions could be degraded by the radicals, leading to the underestimation of ozone concentrations by using the commonly-used protocols. A new protocol with high accuracy and precision was proposed and the rationales for each operational step of the new protocol were explained in detail and supported with justifications. The new protocol was compared with two commonly-used protocols in determining the concentration of ozone in the same water sample treated by the UV/chlorine process at three different UV wavelengths. The wavelength-dependent overestimation/underestimation of the ozone concentrations by using the two commonly-used protocols was well demonstrated and explained by the overlooked interferences of radicals in the protocols.

Arc and pulsed spark discharge inactivation of pathogenic P. aeruginosa, S. aureus, M. canis, T. mentagrophytes, and C. albicans microorganisms.

There is a strong and ever-escalating need for sterilization tools that are effective against a broad range of pathogenic microorganisms. To address this issue, this study evaluates the inactivation potential of arc and pulsed spark plasma discharges on Pseudomonas aeruginosa, Staphylococcus aureus, Microsporum canis, Trichophyton mentagrophytes, and Candida albicans microorganisms. Our results show that the electrical discharge plasma systems are effective in the inactivation of pathogenic microorganisms. The inactivation of the considered strains was greatly affected by the type of microorganisms. Higher viability losses of the pathogenic strains were observed in bacterial strains than in the fungal strains. Moreover, in the case of fungal strains, the population of C. albicans was decreased the most, followed by Trichophyton mentagrophyte, while the population of Microsporum canis was decreased the least. Besides, the arc discharge system was compared with the pulsed spark discharge system. It can be obtained from the results that the pulsed spark discharge treatment successfully enhanced the reduction of the pathogenic cells more than the arc discharge treatment. The higher efficiency of the pulsed spark discharge is due to the generation of discharge streamers on the water surface. The SEM analyses showed that electrical discharge plasmas produced serious damage to pathogenic eukaryotic and prokaryotic microorganisms. Also, the plasma-induced changes in pH values and temperature values were measured. The pulsed spark discharge-treated samples have more significant changes in pH value while arc discharge-treated samples have larger temperature changes.

Recent advances on inactivation of waterborne pathogenic microorganisms by (photo) electrochemical oxidation processes: Design and application strategies

Compared with other conventional water disinfection processes, (photo) electrochemical oxidation (P/ECO) processes have the characteristics of environmental friendliness, convenient installation and operation, easy control and high efficiency of inactivating waterborne pathogenic microorganisms (PMs), so that more and more research work has been focused on this topic, but there is still a huge gap between the research and practical application. Here, the research network of inactivating PMs by P/ECO processes has been comprehensively summarized, and the electrode/reactor/process design strategies based on strengthening direct and indirect oxidation, enhancing mass transfer efficiency and electron transfer efficiency, and improving the effective dose of electrogenerated oxidants are discussed. Furthermore, the factors affecting the inactivation of PMs and the issues regarding to stability and lifetime of the electrode are discussed respectively. Finally, the important research priorities and possible research challenges of P/ECO processes are put forward to make significant progress of this technology.

The effect of chitosan nanoparticles on Escherichia coli viability in drinking water disinfection

Abstract Drinking water disinfection or inactivation of pathogenic microorganisms is an essential step to minimize infection risks and decrease the incidence of waterborne diseases. Recently, chitosan nanoparticles (CNs) have been highlighted as an antimicrobial agent for a wide range of applications due to their natural antimicrobial properties, and low or no toxicity risk for human health. In this study, we generated CNs from three different molecular weight (MW) chitosan (low, medium, high) at various concentrations (0.25, 0.5 and 2% (w/v)). After the CNs preparation and quality assessment, the antimicrobial activity was evaluated by measuring the log reduction of Gram-negative bacteria E. coli as a model microorganism for faecal pollution. The results demonstrated that 0.25% of medium MW CNs are optimal for more than 99.99% reduction of cultivable E. coli and 97% inactivation of metabolically active E. coli. These results indicated that CNs were able to inhibit the growth of cultivable and metabolically active E. coli in tap water and demonstrated the potential use of CNs as an alternative antimicrobial agent in drinking water disinfection.

POSTBIOTICS: A SOLUTION TO PROTECT TROPICAL FRUITS TOWARDS POSTHARVEST ADULTERATION

Food security is threatened by numerous pathogens that cause a variety of foodborne illnesses. The promotion of healthier lifestyles increases the consumption of fresh products such as tropical fruits. Their consumption can expose the consumer to a higher risk of diseases since the fruits do not undergo processing steps to ensure the effective elimination or inactivation of pathogenic microorganisms. Therefore, postharvest treatments are essential for the preservation of the fruit, by reducing the microbial load and lengthening the perch life. Unlike traditional means of postharvest protection, biopreservation of fruits offers the benefits of the natural ecosystems of the microbiome in fruits. The principle of biopreservation is the use of beneficial microorganisms, with the ability to control the growth of other microorganisms, through the production of metabolites known as bacteriocins, postbiotics, metabiotics, paraprobiotics, proteobiotics. These active molecules produced by probiotic bacteria may constitute a safe alternative capable to protect the fruits from deterioration or postharvest damage. The present review described the sources of contamination and deterioration of tropical fruits along with the use of bioactive compounds such as postbiotics as an alternative for fruit protection.

Modeling and validation of delivered fluence of a continuous Dean flow pilot scale UV system: monitoring fluence by biodosimetry approach

The inactivation of pathogenic microorganisms in water and high transmittance liquid foods has been studied extensively. The efficiency of the process is relatively low for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in a simulated opaque fluid (6.5 to 17cm-1) at commercial relevant flow rates (31.70, 63.40, 95.10 gph) using a pilot-scale Dean Flow UV system. In this study, a mathematical model for the prediction of delivered fluence was developed by the biodosimetry method. The results revealed that increased Reduction equivalent fluence (REF) rates were observed with increased flow rates due to additional turbulence. The experimental and calculated REF were well correlated with the UV-C absorption coefficient range of 6.5 to 17cm-1 indicating efficient mixing in the reactor. REF scaled up linearly at experimental conditions as an inverse function of flow rate and absorption coefficient, and a linear mathematical model (R2>0.99, p<0.05) to predict delivered REF was developed. The model was tested and validated against independent experiments using Salmonella Typhimurium and Bacillus cereus endospores. The predicted and experimental REF values were in close agreement (p>0.05). It is demonstrated that the developed model can predict the REF, thus microbial inactivation of microbial suspensions in simulated fluid with the absorption coefficient of 6.5-17cm-1 and flow rates of 31.70-95.10 gph. The pilot system will be field-tested against microorganisms in highly absorbing and scattering fluids.

Sonophotodynamic Inactivation: The power of light and ultrasound in the battle against microorganisms

The inactivation of pathogenic microorganisms that are a threat to the human being is an old challenge that needs to be overcome, mainly because microorganisms are able to develop resistance that leads to the failure of the treatment. Moreover, the biofilm living form is a complex microorganism community that is less susceptible to antimicrobials agents. For this reason, the search for alternative therapies that are not able to induce resistance and have the ability to inactivate the biofilms is unquestionably needed. In this review, Photodynamic and Sonodynamic Inactivation (PDI and SDI) are suggested as promising antimicrobial approaches. However, the use of the combined therapy, called Sonophotodynamic Inactivation (SPDI), is reinforced and encouraged for microbial diseases. As long as SPDI has been demonstrated to be more effective in inactivating microorganisms than PDI and SDI, it is allowed to reduce the time and parameters of the treatment, turning this therapy safer for mammalian cells.

Use of Ultrasound and Ultraviolet Radiation in Hybrid Methods for Water Disinfection

Hybrid photochemical methods are considered for water disinfection in which treatment with ultraviolet (UV) and ultrasonic (US) radiations are combined (US/UV) and applied consecutively or simultaneously; the use of catalysts is also included. The literature survey shows that inactivation of pathogenic microorganisms in aquatic media by high-frequency US (>100 kHz) has not been studied adequately, whereas only low-frequency (<100 kHz) US and low-pressure mercury vapor lamps (254 nm) were used in hybrid US/UV methods. Irradiation with high-frequency US generates reactive oxygen species (primarily hydroxyl radicals) in greater proportions, and a synergistic effect is observed when UV irradiation is included in treatment. Therefore, the use of high-frequency US and mercury-free UV sources in hybrid oxidizing systems, including those based on Fenton-like processes, is promising for intensifying disinfection processes and improving their effectiveness.

Microbial Contamination of Fresh Produce: What, Where, and How?

Promotion of healthier lifestyles has led to an increase in consumption of fresh produce. Such foodstuffs may expose consumers to increased risk of foodborne disease, as often they are not subjected to processing steps to ensure effective removal or inactivation of pathogenic microorganisms before consumption. Consequently, reports of ready-to-eat fruit and vegetable related disease outbreak occurrences have increased substantially in recent years, and information regarding these events is often not readily available. Identifying the nature and source of microbial contamination of these foodstuffs is critical for developing appropriate mitigation measures to be implemented by food producers. This review aimed to identify the foodstuffs most susceptible to microbial contamination and the microorganisms responsible for disease outbreaks from information available in peer-reviewed scientific publications. A total of 571 outbreaks were identified from 1980 to 2016, accounting for 72,855 infections and 173 deaths. Contaminated leafy green vegetables were responsible for 51.7% of reported outbreaks. Contaminated soft fruits caused 27.8% of infections. Pathogenic strains of Escherichia coli and Salmonella, norovirus, and hepatitis A accounted for the majority of cases. Large outbreaks resulted in particular biases such as the observation that contaminated sprouted plants caused 31.8% of deaths. Where known, contamination mainly occurred via contaminated seeds, water, and contaminated food handlers. There is a critical need for standardized datasets regarding all aspects of disease outbreaks, including how foodstuffs are contaminated with pathogenic microorganisms. Providing food business operators with this knowledge will allow them to implement better strategies to improve safety and quality of fresh produce.

Availability of nutrients, removal of nicotine, heavy metals and pathogens in compounds obtained from smuggled cigarette tobacco compost associated with industrial sewage sludge

This study evaluated the chemical and microbiological properties of the compost obtained from the tobacco of smuggled cigarettes (SCT) and industrial sewage sludge (ISS). The composting was carried out in three reactors from different combinations of residues. The compost was analyzed to verify the percentage of nicotine removal, heavy metals, nutrient content and the inactivation of pathogenic microorganisms. The concentration of heavy metals: Ni, Cd, Cr, Pb, Cu, Zn, Fe and Mn in the composts obtained from the three reactors was below the values set for their use in soils. The NPK content ranged between 8.31% and 12.43%, indicating that the compost produced can add nutritional benefits to the plants. The nicotine removal, 72.6% (R1), 96.4% (R2) and 99.6% (R3) indicated efficiency of the composting process in reactors in the degradation of this substance. The results of pathogenic microorganism analysis showed that the three composts obtained from reactors R1, R2 and R3 met the sanitation standards for agricultural use according to the normative of maximum limits of contaminants allowed in organic compounds. These results show that the treatment of SCT and ISS by the process of composting in reactors may be an ecologically viable alternative.

Effectiveness of visible and ultraviolet light emitting diodes for inactivation of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli: A comparative study

The rapid use of ultraviolet light emitting diodes (UV-LEDs) in various disinfection applications is growing tremendously due to their advantages unachievable using UV lamps. In this study, a comparison of standard LED at 460 nm wavelength and UVA LED at 385 nm was conducted to determine their effectiveness in disinfection of frequently isolated pathogens in hospitals (Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli). Determination of disinfection efficiency was carried out by measuring inhibition zone. Effects of varied exposure time on the inactivation of pathogenic microorganisms was studied. The results demonstrated that LED does not have germicidal activities. The highest inactivation for UVA LED was achieved for Pseudomonas aeruginosa. Linear relationship was found between exposure time and log reduction. This study showed that UVA LEDs can effectively inactivate significantly higher number of microorganisms hence can be used in disinfection of various applications.

Comparative ecotoxicological evaluation of peracetic acid and the active chlorine of calcium hypochlorite: Use of Dugesia tigrina as a bioindicator of environmental pollution

Chlorine plays a primary role in the disinfection of drinking water and wastewater due to its effectiveness as a biocide; however, there is evidence of the formation of toxic byproducts from its application, and this has promoted the search for alternatives. Alternative disinfectants can be effective in the inactivation of pathogenic microorganisms and are less damaging to human health and aquatic ecosystems. However, more information is needed on the effect of residual concentrations on the environment. This work compares the ecotoxicological effects of PAA disinfectants and the active chlorine of calcium hypochlorite in relation to the organism Dugesia tigrina (planaria), in terms of the acute effects: LC50, and chronic effects: feeding, locomotion, regeneration, reproduction and fertility. The results indicated that the active chlorine was more toxic than PAA, with LC50 (96 h) of 2.63 mg.L-1 and 3.16 mg.L-1, respectively. Sub-lethal exposure to active chlorine was more toxic when compared to PAA, and there was evidence of significantly reduced feeding and locomotion, causing a greater delay in regeneration and impairment in reproduction and fertility. The results allowed the comparison of the two disinfectants using half-life constants of the compounds and the lowest observed effect level (LOEC) of the oxidants. Chlorine represents a greater risk to the ecosystem for a longer period. The results obtained in this study can help in the establishment of discharge limits for PAA in water bodies.