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1
LeChevallier, Mark W., Cheryl D. Cawthon und Ramon G. Lee. „Mechanisms of Bacterial Survival in Chlorinated Drinking Water“. Water Science and Technology 20, Nr. 11-12 (01.11.1988): 145–51. http://dx.doi.org/10.2166/wst.1988.0277.
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Experiments showed that attachment of bacteria to surfaces provided the greatest increase in disinfection resistance. Attachment of high nutrient grown, unencapsulated, Klebsiellapneumoniae to glass microscope slides afforded the microorganisms as much as a 150 fold increase in disinfection resistance. Other mechanisms which increased disinfection resistance included: the age of the biofilm, bacterial encapsulation and previous growth conditions (e.g. growth medium, and growth temperature). These factors increased chlorine resistance from two to ten fold. The choice of disinfectant residual was shown to influence the type of resistance mechanism observed. Disinfection by free chlorine was affected by surfaces, age of the biofilm, encapsulation and nutrient effects. Disinfection by monochloramine, however, was only affected by surfaces. Importantly, the research showed that these resistance mechanisms were multiplicative (e.g. the resistance provided by one mechanism could be multiplied by the resistance provided by a second). These results provide important insights to understand the survival of bacteria in chlorinated drinking water supplies.
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Bichai, Françoise, Simon Léveillé und Benoit Barbeau. „Comparison of the role of attachment, aggregation and internalisation of microorganisms in UVC and UVA (solar) disinfection“. Water Science and Technology 63, Nr. 9 (01.05.2011): 1823–31. http://dx.doi.org/10.2166/wst.2011.385.
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In this comparative study, the impact of two microbial protective mechanisms against simulated UVA disinfection was assessed by using protocols previously developed for UVC disinfection assays. (i) The impact of natural microorganism aggregation and attachment to particles was assessed by targeting total coliform bacteria in natural surface water samples. (ii) The impact of bacteria internalisation by zooplankton was assessed by using C. elegans nematodes as a model host and E. coli as a bacterial target for UVA inactivation. Dispersion of natural aggregates by blending prior to UVA exposure was shown to enhance the inactivation rate of total coliforms as compared to untreated raw water. Removal of particles by an 8-μm membrane filtration did not improve UVA disinfection efficiency. Twenty-four per cent of the highest applied UVA fluence was found to reach internalised E. coli in nematodes. Both aggregation and internalisation showed similar impact as protective mechanisms against UVA and UVC bacterial inactivation.
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Mecha, Achisa C., Maurice S. Onyango, Aoyi Ochieng und Maggy NB Momba. „Modelling inactivation kinetics of waterborne pathogens in municipal wastewater using ozone“. Environmental Engineering Research 25, Nr. 6 (06.12.2019): 890–97. http://dx.doi.org/10.4491/eer.2019.432.
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Microbial water pollution is a key concern leading to waterborne diseases. This study evaluated the disinfection of wastewater using ozonation. The following aspects were investigated: inactivation efficiency against <i>Escherichia coli, Salmonella</i> species, <i>Shigella</i> species, and <i>Vibrio cholerae</i>; modelling of inactivation kinetics using disinfection models; and evaluation of microbial regrowth studies. 99% bacterial inactivation was obtained within 15 min, irrespective of the water matrix, showing the strong oxidizing potential of ozone. The disinfection data were fitted into the log-linear and Weibull models. The survival curves were non-linear and fitted the Weibull model (fractional bias and normalized mean square error equal to 0.0), especially at high bacterial concentrations (10<sup>6</sup> CFU/mL). The inactivation occurred in two stages: an initial rapid stage (15 min) and a final slow stage exhibiting a tailing mechanism (15-45 min) probably as a result of the self-defence mechanisms adopted by the bacteria to limit oxidative stress. Considering the pattern of survival curves, no significant differences (<i>p</i> > 0.05) were observed among the four tested bacterial species; thus showing that ozone was effective against all the bacteria tested. There was minimal bacterial regrowth in the treated samples 24 h after ozone disinfection with reactivation values of 0-5% obtained.
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Cogan, N. G., Jason Brown, Kyle Darres und Katherine Petty. „Optimal Control Strategies for Disinfection of Bacterial Populations with Persister and Susceptible Dynamics“. Antimicrobial Agents and Chemotherapy 56, Nr. 9 (02.07.2012): 4816–26. http://dx.doi.org/10.1128/aac.00675-12.
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ABSTRACTIt is increasingly clear that bacteria manage to evade killing by antibiotics and antimicrobials in a variety of ways, including mutation, phenotypic variations, and formation of biofilms. With recent advances in understanding the dynamics of the tolerance mechanisms, there have been subsequent advances in understanding how to manipulate the bacterial environments to eradicate the bacteria. This study focuses on using mathematical techniques to find the optimal disinfection strategy to eliminate the bacteria while managing the load of antibiotic that is applied. In this model, the bacterial population is separated into those that are tolerant to the antibiotic and those that are susceptible to disinfection. There are transitions between the two populations whose rates depend on the chemical environment. Our results extend previous mathematical studies to include more realistic methods of applying the disinfectant. The goal is to provide experimentally testable predictions that have been lacking in previous mathematical studies. In particular, we provide the optimal disinfection protocol under a variety of assumptions within the model that can be used to validate or invalidate our simplifying assumptions and the experimental hypotheses that we used to develop the model. We find that constant dosing is not the optimal method for disinfection. Rather, cycling between application and withdrawal of the antibiotic yields the fastest killing of the bacteria.
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Delebecque, Nathalie, Christel Causserand, Christine Roques und Pierre Aimar. „Membrane processes for water disinfection: investigation on bacterial transfer mechanisms“. Desalination 199, Nr. 1-3 (November 2006): 81–83. http://dx.doi.org/10.1016/j.desal.2006.03.147.
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Cunningham, J. H., C. Cunningham, B. Van Aken und L. S. Lin. „Feasibility of disinfection kinetics and minimum inhibitory concentration determination on bacterial cultures using flow cytometry“. Water Science and Technology 58, Nr. 4 (01.09.2008): 937–44. http://dx.doi.org/10.2166/wst.2008.619.
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Disinfection kinetics has been well established for selected antimicrobial agents on isolated bacterial strains. Due to the difficulties of culturing most bacteria, the majority of these studies have been limited to readily cultivable microorganisms of a single type or family. This study explores the feasibility of using flow cytometry for characterising the disinfection kinetics and minimum inhibitory concentration (MIC) of an Escherichia coli culture and a microbial consortium. The proposed method relies on fluorescent dye molecules to indicate the morphological and physiological status of numerous individual cells. Biocides of varying effectiveness and inactivation mechanisms (chlorine, iodine, and silver) were used to evaluate this novel application. Using pseudo-first-order kinetics, the coefficients of specific lethality of chlorine and iodine on Escherichia coli were 4.71 and 3.78×10−3 L mg−1 min−1 and MIC of silver ion was between 60 and 80 μg L−1. The coefficients of specific lethality of chlorine and iodine on the microbial consortium were 4.96 and 8.89×10−3 L mg−1 min−1 and MIC of silver ion was between 40 and 60 μg L−1. This method can be used to provide a rapid and consistent way of determining disinfection kinetics and MICs for pure and mixed bacterial cultures and can potentially be used to examine water and wastewater disinfection efficiency. However, caution should be used to ensure that the physiological and morphological status characterised by cytodyes is a result of the inactivation mechanisms of the disinfectants evaluated.
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Dias, D. F. C., R. G. Passos und M. von Sperling. „A review of bacterial indicator disinfection mechanisms in waste stabilisation ponds“. Reviews in Environmental Science and Bio/Technology 16, Nr. 3 (09.05.2017): 517–39. http://dx.doi.org/10.1007/s11157-017-9433-2.
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Rosenblueth, Mónica, und Esperanza Martínez-Romero. „Bacterial Endophytes and Their Interactions with Hosts“. Molecular Plant-Microbe Interactions® 19, Nr. 8 (August 2006): 827–37. http://dx.doi.org/10.1094/mpmi-19-0827.
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Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seed-borne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endo-phytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.
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Garcia-Segura, Sergi, Omotayo A. Arotiba und Enric Brillas. „The Pathway towards Photoelectrocatalytic Water Disinfection: Review and Prospects of a Powerful Sustainable Tool“. Catalysts 11, Nr. 8 (29.07.2021): 921. http://dx.doi.org/10.3390/catal11080921.
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Photoelectrocatalysis is a hybrid photon/electron-driven process that benefits from the synergistic effects of both processes to enhance and stabilize the generation of disinfecting oxidants. Photoelectrocatalysis is an easy to operate technology that can be scaled-up or scaled-down for various water treatment applications as low-cost decentralized systems. This review article describes the fundamentals of photoelectrocatalysis, applied to water disinfection to ensure access to clean water for all as a sustainable development goal. Advances in reactor engineering design that integrate light-delivery and electrochemical system requirements are presented, with a description of photo-electrode material advances, including doping, nano-decoration, and nanostructure control. Disinfection and cell inactivation are described using different model microorganisms such as E. coli, Mycobacteria, Legionella, etc., as well the fungus Candida parapsilosis, with relevant figures of merit. The key advances in the elucidation of bacterial inactivation mechanisms by photoelectrocatalytic treatments are presented and knowledge gaps identified. Finally, prospects and further research needs are outlined, to define the pathway towards the future of photoelectrocatalytic disinfection technologies.
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Liu, Dan, Yiqin Mao und Lijun Ding. „Carbon nanotubes as antimicrobial agents for water disinfection and pathogen control“. Journal of Water and Health 16, Nr. 2 (12.02.2018): 171–80. http://dx.doi.org/10.2166/wh.2018.228.
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Abstract Waterborne diseases significantly affect human health and are responsible for high mortality rates worldwide. Antibiotics have been known for decades for treatment of bacterial strains and their overuse and irrational applications are causing increasing bacteria resistance. Therefore, there is a strong need to find alternative ways for efficient water disinfection and microbial control. Carbon nanotubes (CNTs) have demonstrated strong antimicrobial properties due to their remarkable structure. This paper reviews the antimicrobial properties of CNTs, discusses diverse mechanisms of action against microorganisms as well as their applicability for water disinfection and microbial control. Safety concerns, challenges of CNTs as antimicrobial agents and future opportunities for their application in the water remediation process are also highlighted.
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Kiwi, John, und Sami Rtimi. „Mechanisms of the Antibacterial Effects of TiO2–FeOx under Solar or Visible Light: Schottky Barriers versus Surface Plasmon Resonance“. Coatings 8, Nr. 11 (04.11.2018): 391. http://dx.doi.org/10.3390/coatings8110391.
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This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. The interaction between the film active surface species and the bacteria within the disinfection period was followed by X-ray photoelectron spectroscopy (XPS) and provided the evidence for a redox catalysis taking place during the bacterial inactivation time. The optical and surface properties of the films were evaluated by appropriate surface analytical methods. A differential mechanism is suggested for each specific microstructure inducing bacterial inactivation. The surface FeOx plasmon resonance transferred electrons into the conduction band of TiO2 because of the Schottky barrier after Fermi level equilibration of the two components. An electric field at the interface between TiO2 and FeOx, favors the separation of the photo-generated charges leading to a faster bacterial inactivation by TiO2–FeOx compared to the bacterial inactivation kinetics by each of the single oxides.
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Liu, Lei, Geof Hall und Pascale Champagne. „Disinfection processes and mechanisms in wastewater stabilization ponds: a review“. Environmental Reviews 26, Nr. 4 (Dezember 2018): 417–29. http://dx.doi.org/10.1139/er-2018-0006.
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Wastewater stabilization ponds (WSPs) have been proven to be economical alternatives to conventional wastewater treatment technologies due to their unique advantages including ease of operation, minimal energy input, and minimal maintenance requirements. Their reported high pathogen removal efficiencies have made WSPs a popular choice for wastewater treatment, especially as tertiary lagoons. This paper provides a critical overview of the various disinfection processes and mechanisms that occur in WSPs. A thorough review of the removal or attenuation mechanisms for bacterial, viral, protozoan, and helminthic pathogens is presented. Factors that impact the removal efficiency of pathogenic organisms may include sunlight, pH, dissolved oxygen, temperature, sedimentation, attachment, hydraulic retention time, pond depth, predation and nutrient availability; the relationship between these factors is also discussed. The purpose of this review paper is to utilize the current understanding of pathogen removal mechanisms in pond systems to improve the operation and design of WSPs, and more importantly, to provide guidance for the definition of regulations with respect to pathogen removal in eco-engineered wastewater treatment systems such as WSPs.
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Zhang, Shuai, Yue Wang, Ji Lu, Zhigang Yu, Hailiang Song, Philip L. Bond und Jianhua Guo. „Chlorine disinfection facilitates natural transformation through ROS-mediated oxidative stress“. ISME Journal 15, Nr. 10 (03.05.2021): 2969–85. http://dx.doi.org/10.1038/s41396-021-00980-4.
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AbstractThe bacterial infection that involves antimicrobial resistance is a rising global threat to public health. Chlorine-based water disinfection processes can inactivate antibiotic resistant bacteria. However, at the same time, these processes may cause the release of antibiotic resistance genes into the water as free DNA, and consequently increase the risk to disseminate antibiotic resistance via natural transformation. Presently, little is known about the contribution of residual chlorine affecting the transformation of extracellular antibiotic resistance genes (ARGs). This study investigates whether chloramine and free chlorine promote the transformation of ARGs and how this may occur. We reveal that both chloramine and free chlorine, at practically relevant concentrations, significantly stimulated the transformation of plasmid-encoded ARGs by the recipient Acinetobacter baylyi ADP1, by up to a 10-fold increase. The underlying mechanisms underpinning the increased transformations were revealed. Disinfectant exposure induced a series of cell responses, including increased levels of reactive oxygen species (ROS), bacterial membrane damage, ROS-mediated DNA damage, and increased stress response. These effects thus culminated in the enhanced transformation of ARGs. This promoted transformation was observed when exposing disinfectant-pretreated A. baylyi to free plasmid. In contrast, after pretreating free plasmid with disinfectants, the transformation of ARGs decreased due to the damage of plasmid integrity. These findings provide important insight on the roles of disinfectants affecting the horizontal transfer of ARGs, which could be crucial in the management of antibiotic resistance in our water systems.
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Cherchi, C., und A. Z. Gu. „Effect of bacterial growth stage on resistance to chlorine disinfection“. Water Science and Technology 64, Nr. 1 (01.07.2011): 7–13. http://dx.doi.org/10.2166/wst.2011.536.
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The mechanisms and factors that affect microbial resistance to chlorine disinfection have not been fully elucidated. In this study, we investigated the impact of the cell growth stage on chlorine disinfection efficiency. Specifically, we evaluated the impact of the growth stage on chlorination resistance by comparing the inactivation efficiencies of two indicator bacterial strains (Escherichia coli K12 and Escherichia coli 0157:H7) obtained from various growth phases, using Chick-Watson kinetic parameters. For both E. coli strains (K12 and 0157:H7), the inactivation rate constants are the lowest at stationary phase (0.19 and 0.32) compared to those at initial lag (0.54 and 0.76) and exponential growth phase (0.63 and 0.69), respectively. These results suggested that the abundance of resistant subpopulations increases at stressed stationary conditions and E. coli cells obtained from the stationary growth phase exhibited more resistance and lower inactivation efficiency compared to those from the lag and exponential phases. This implies that microbes in wastewater treatment process with varying solids retention times (SRTs, which indicate growth rates) may show different extents of chlorine resistance. Comparison of the coefficient of dilution (n) values in both E. coli strains for the various growth phases suggest that cells seem to be more sensitive to disinfectant concentration at the stationary-lag phase than that at the exponential stage. Comparing the two E. coli strains, higher inactivation rates were observed for the pathogenic O157:H7 than for K12 at different stages of growth. The strain-to-strain variability in survivability to chlorine exposure has to be considered when selecting indicator microorganisms for water quality monitoring.
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Gomez-Alvarez, Vicente, Randy P. Revetta und Jorge W. Santo Domingo. „Metagenomic Analyses of Drinking Water Receiving Different Disinfection Treatments“. Applied and Environmental Microbiology 78, Nr. 17 (22.06.2012): 6095–102. http://dx.doi.org/10.1128/aem.01018-12.
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ABSTRACTA metagenome-based approach was used to assess the taxonomic affiliation and function potential of microbial populations in free-chlorine-treated (CHL) and monochloramine-treated (CHM) drinking water (DW). In all, 362,640 (averaging 544 bp) and 155,593 (averaging 554 bp) pyrosequencing reads were analyzed for the CHL and CHM samples, respectively. Most annotated proteins were found to be of bacterial origin, although eukaryotic, archaeal, and viral proteins were also identified. Differences in community structure and function were noted. Most notably,Legionella-like genes were more abundant in the CHL samples while mycobacterial genes were more abundant in CHM samples. Genes associated with multiple disinfectant mechanisms were identified in both communities. Moreover, sequences linked to virulence factors, such as antibiotic resistance mechanisms, were observed in both microbial communities. This study provides new insights into the genetic network and potential biological processes associated with the molecular microbial ecology of DW microbial communities.
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Achinas, Spyridon, Nikolaos Charalampogiannis und Gerrit Jan Willem Euverink. „A Brief Recap of Microbial Adhesion and Biofilms“. Applied Sciences 9, Nr. 14 (12.07.2019): 2801. http://dx.doi.org/10.3390/app9142801.
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Food and beverage industries operate their production units under stringent hygiene standards to verify high-quality products. However, the presence of biofilms can cause hygienic problems in the industries in the case of pathogenic organisms. Microorganisms can form biofilms, which are resistant to cleaning and disinfection. Microorganisms in biofilms are closely packed in a matrix that acts as a barrier to cleaning and disinfection. Biofilms are observed in processing equipment and open surfaces, resulting in food safety problems or weakening of production efficiency. This review provides a recap of the biofouling process, including the production mechanisms and control techniques of microbial adhesion. Microbial adhesion and colonization are the sine qua non of the establishment of bacterial pathogenesis and this report focuses on their prevention.
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Slade, J. S. „Viruses and Bacteria in a Chalk Well“. Water Science and Technology 17, Nr. 10 (01.10.1985): 111–25. http://dx.doi.org/10.2166/wst.1985.0102.
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Human enteroviruses have been found in water from a chalk well with history of excellent bacteriological and organoleptic quality. A proportion of these viruses survived disinfection treatment which consisted of a nominal 1 mg/ℓ of free chlorine maintained for a minimum contact period of 15 minutes at a pH value of 7.2. It is concluded that viruses may occur in underground sources which have consistently proved to be satisfactory in routine monitoring tests for bacterial indicators of faecal pollution. Possible mechanisms which these circumstances may arise are discussed.
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Nigam, Yamni, Alyson Bexfield, Stephen Thomas und Norman Arthur Ratcliffe. „Maggot Therapy: The Science and Implication for CAM Part I—History and Bacterial Resistance“. Evidence-Based Complementary and Alternative Medicine 3, Nr. 2 (2006): 223–27. http://dx.doi.org/10.1093/ecam/nel021.
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It is now a universally acknowledged fact that maggot therapy can be used successfully to treat chronic, long-standing, infected wounds, which have previously failed to respond to conventional treatment. Such wounds are typically characterized by the presence of necrotic tissue, underlying infection and poor healing. Maggot therapy employs the use of freshly emerged, sterile larvae of the common green-bottle fly,Phaenicia(Lucilia)sericata, and is a form of artificially induced myiasis in a controlled clinical situation. In this review article, we will discuss the role of maggots and their preparation for clinical use. Maggot therapy has the following three core beneficial effects on a wound: debridement, disinfection and enhanced healing. In part I we explore our current understanding of the mechanisms underlying these effects.
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Vikram, Amit, Jennifer M. Bomberger und Kyle J. Bibby. „Efflux as a Glutaraldehyde Resistance Mechanism in Pseudomonas fluorescens and Pseudomonas aeruginosa Biofilms“. Antimicrobial Agents and Chemotherapy 59, Nr. 6 (30.03.2015): 3433–40. http://dx.doi.org/10.1128/aac.05152-14.
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ABSTRACTA major challenge in microbial biofilm control is biocide resistance. Phenotypic adaptations and physical protective effects have been historically thought to be the primary mechanisms for glutaraldehyde resistance in bacterial biofilms. Recent studies indicate the presence of genetic mechanisms for glutaraldehyde resistance, but very little is known about the contributory genetic factors. Here, we demonstrate that efflux pumps contribute to glutaraldehyde resistance inPseudomonas fluorescensandPseudomonas aeruginosabiofilms. The RNA-seq data show that efflux pumps and phosphonate degradation, lipid biosynthesis, and polyamine biosynthesis metabolic pathways were induced upon glutaraldehyde exposure. Furthermore, chemical inhibition of efflux pumps potentiates glutaraldehyde activity, suggesting that efflux activity contributes to glutaraldehyde resistance. Additionally, induction of known modulators of biofilm formation, including phosphonate degradation, lipid biosynthesis, and polyamine biosynthesis, may contribute to biofilm resistance and resilience. Fundamental understanding of the genetic mechanism of biocide resistance is critical for the optimization of biocide use and development of novel disinfection strategies. Our results reveal genetic components involved in glutaraldehyde resistance and a potential strategy for improved control of biofilms.
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Stawarz-Janeczek, Magdalena, Agata Kryczyk-Poprawa, Bożena Muszyńska, Włodzimierz Opoka und Jolanta Pytko-Polończyk. „Disinfectants Used in Stomatology and SARS-CoV-2 Infection“. European Journal of Dentistry 15, Nr. 02 (10.03.2021): 388–400. http://dx.doi.org/10.1055/s-0041-1724154.
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AbstractEffective disinfection is a basic procedure in medical facilities, including those conducting dental surgeries, where treatments for tissue discontinuity are also performed, as it is an important element of infection prevention. Disinfectants used in dentistry and dental and maxillofacial surgery include both inorganic (hydrogen peroxide, sodium chlorite-hypochlorite) and organic compounds (ethanol, isopropanol, peracetic acid, chlorhexidine, eugenol). Various mechanisms of action of disinfectants have been reported, which include destruction of the structure of bacterial and fungal cell membranes; damage of nucleic acids; denaturation of proteins, which in turn causes inhibition of enzyme activity; loss of cell membrane integrity; and decomposition of cell components. This article discusses the most important examples of substances used as disinfectants in dentistry and presents the mechanisms of their action with particular focus on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The search was conducted in ScienceDirect, PubMed, and Scopus databases. The interest of scientists in the use of disinfectants in dental practice is constantly growing, which results in the increasing number of publications on disinfection, sterilization, and asepsis. Many disinfectants often possess several of the abovementioned mechanisms of action. In addition, disinfectant preparations used in dental practice either contain one compound or are frequently a mixture of active compounds, which increases their range and effectiveness of antimicrobial action. Currently available information on disinfectants that can be used to prevent SARS-CoV-2 infection in dental practices was summarized.
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Chaturvedi, Shalini, und Pragnesh N. Dave. „Environmental Application of Photocatalysis“. Materials Science Forum 734 (Dezember 2012): 273–94. http://dx.doi.org/10.4028/www.scientific.net/msf.734.273.
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Recent interest and studies in environmental photo-chemistry, in natural photosynthesis, and chemical methods for solar energy transformations has contributed greatly to our knowledge and understanding of the various phenomena related to both photo-chemistry and catalysis. As an emerging nanotechnology come together with the chemical mechanisms of photo-catalysis, the photo-catalytic nanoparticle titanium dioxide offers a new meaning of remediation and degradation on volatile organic compounds in the aqueous and airs streams. In this chapter we discuss about application of photocatalysis in environment like biological contamination, air purification, water disinfection, hazardous waste remediation, water purification, self-clean buildings, deodorizing, anti-bacterial action, anti-fogging resolving cleaning action etc.
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Sherchan, Samendra, Syreeta Miles, Luisa Ikner, Hye-Weon Yu, Shane Snyder und Ian Pepper. „Near Real-Time Detection of E. coli in Reclaimed Water“. Sensors 18, Nr. 7 (16.07.2018): 2303. http://dx.doi.org/10.3390/s18072303.
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Advanced treatment of reclaimed water prior to potable reuse normally results in the inactivation of bacterial populations, however, incremental treatment failure can result in bacteria, including pathogens, remaining viable. Therefore, potential microorganisms need to be detected in real-time to preclude potential adverse human health effects. Real-time detection of microbes presents unique problems which are dependent on the water quality of the test water, including parameters such as particulate content and turbidity, and natural organic matter content. In addition, microbes are unusual in that: (i) viability and culturability are not always synonymous; (ii) viability in water can be reduced by osmotic stress; and (iii) bacteria can invoke repair mechanisms in response to UV disinfection resulting in regrowth of bacterial populations. All these issues related to bacteria affect the efficacy of real-time detection for bacteria. Here we evaluate three different sensors suitable for specific water qualities. The sensor A is an on-line, real-time sensor that allows for the continuous monitoring of particulates (including microbial contaminants) using multi-angle-light scattering (MALS) technology. The sensor B is a microbial detection system that uses optical technique, Mie light scattering, for particle sizing and fluorescence emission for viable bacteria detection. The last sensor C was based on adenosine triphosphate (ATP) production. E. coli was used a model organism and out of all tested sensors, we found the sensor C to be the most accurate. It has a great potential as a surrogate parameter for microbial loads in test waters and be useful for process control in treatment trains.
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Razzokov, Jamoliddin, Maksudbek Yusupov und Annemie Bogaerts. „Possible Mechanism of Glucose Uptake Enhanced by Cold Atmospheric Plasma: Atomic Scale Simulations“. Plasma 1, Nr. 1 (08.06.2018): 119–25. http://dx.doi.org/10.3390/plasma1010011.
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Cold atmospheric plasma (CAP) has shown its potential in biomedical applications, such as wound healing, cancer treatment and bacterial disinfection. Recent experiments have provided evidence that CAP can also enhance the intracellular uptake of glucose molecules which is important in diabetes therapy. In this respect, it is essential to understand the underlying mechanisms of intracellular glucose uptake induced by CAP, which is still unclear. Hence, in this study we try to elucidate the possible mechanism of glucose uptake by cells by performing computer simulations. Specifically, we study the transport of glucose molecules through native and oxidized membranes. Our simulation results show that the free energy barrier for the permeation of glucose molecules across the membrane decreases upon increasing the degree of oxidized lipids in the membrane. This indicates that the glucose permeation rate into cells increases when the CAP oxidation level in the cell membrane is increased.
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Galler, Kerstin M., Manuel Weber, Yüksel Korkmaz, Matthias Widbiller und Markus Feuerer. „Inflammatory Response Mechanisms of the Dentine–Pulp Complex and the Periapical Tissues“. International Journal of Molecular Sciences 22, Nr. 3 (02.02.2021): 1480. http://dx.doi.org/10.3390/ijms22031480.
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The macroscopic and microscopic anatomy of the oral cavity is complex and unique in the human body. Soft-tissue structures are in close interaction with mineralized bone, but also dentine, cementum and enamel of our teeth. These are exposed to intense mechanical and chemical stress as well as to dense microbiologic colonization. Teeth are susceptible to damage, most commonly to caries, where microorganisms from the oral cavity degrade the mineralized tissues of enamel and dentine and invade the soft connective tissue at the core, the dental pulp. However, the pulp is well-equipped to sense and fend off bacteria and their products and mounts various and intricate defense mechanisms. The front rank is formed by a layer of odontoblasts, which line the pulp chamber towards the dentine. These highly specialized cells not only form mineralized tissue but exert important functions as barrier cells. They recognize pathogens early in the process, secrete antibacterial compounds and neutralize bacterial toxins, initiate the immune response and alert other key players of the host defense. As bacteria get closer to the pulp, additional cell types of the pulp, including fibroblasts, stem and immune cells, but also vascular and neuronal networks, contribute with a variety of distinct defense mechanisms, and inflammatory response mechanisms are critical for tissue homeostasis. Still, without therapeutic intervention, a deep carious lesion may lead to tissue necrosis, which allows bacteria to populate the root canal system and invade the periradicular bone via the apical foramen at the root tip. The periodontal tissues and alveolar bone react to the insult with an inflammatory response, most commonly by the formation of an apical granuloma. Healing can occur after pathogen removal, which is achieved by disinfection and obturation of the pulp space by root canal treatment. This review highlights the various mechanisms of pathogen recognition and defense of dental pulp cells and periradicular tissues, explains the different cell types involved in the immune response and discusses the mechanisms of healing and repair, pointing out the close links between inflammation and regeneration as well as between inflammation and potential malignant transformation.
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Malik, Erum, David A. Phoenix, Timothy J. Snape, Frederick Harris, Jaipaul Singh, Leslie H. G. Morton und Sarah R. Dennison. „Linearized esculentin-2EM shows pH dependent antibacterial activity with an alkaline optimum“. Molecular and Cellular Biochemistry 476, Nr. 10 (06.06.2021): 3729–44. http://dx.doi.org/10.1007/s11010-021-04181-7.
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AbstractHere the hypothesis that linearized esculentin 2EM (E2EM-lin) from Glandirana emeljanovi possesses pH dependent activity is investigated. The peptide showed weak activity against Gram-negative bacteria (MLCs ≥ 75.0 μM) but potent efficacy towards Gram-positive bacteria (MLCs ≤ 6.25 μM). E2EM-lin adopted an α-helical structure in the presence of bacterial membranes that increased as pH was increased from 6 to 8 (↑ 15.5–26.9%), whilst similar increases in pH enhanced the ability of the peptide to penetrate (↑ 2.3–5.1 mN m−1) and lyse (↑ 15.1–32.5%) these membranes. Theoretical analysis predicted that this membranolytic mechanism involved a tilted segment, that increased along the α-helical long axis of E2EM-lin (1–23) in the N → C direction, with − < µH > increasing overall from circa − 0.8 to − 0.3. In combination, these data showed that E2EM-lin killed bacteria via novel mechanisms that were enhanced by alkaline conditions and involved the formation of tilted and membranolytic, α-helical structure. The preference of E2EM-lin for Gram-positive bacteria over Gram-negative organisms was primarily driven by the superior ability of phosphatidylglycerol to induce α-helical structure in the peptide as compared to phosphatidylethanolamine. These data were used to generate a novel pore-forming model for the membranolytic activity of E2EM-lin, which would appear to be the first, major reported instance of pH dependent AMPs with alkaline optima using tilted structure to drive a pore-forming process. It is proposed that E2EM-lin has the potential for development to serve purposes ranging from therapeutic usage, such as chronic wound disinfection, to food preservation by killing food spoilage organisms.
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Klämpfl, Tobias G., Georg Isbary, Tetsuji Shimizu, Yang-Fang Li, Julia L. Zimmermann, Wilhelm Stolz, Jürgen Schlegel, Gregor E. Morfill und Hans-Ulrich Schmidt. „Cold Atmospheric Air Plasma Sterilization against Spores and Other Microorganisms of Clinical Interest“. Applied and Environmental Microbiology 78, Nr. 15 (11.05.2012): 5077–82. http://dx.doi.org/10.1128/aem.00583-12.
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ABSTRACTPhysical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungusCandida albicans, were tested. Thirty seconds of plasma treatment led to a 4 to 6 log10CFU reduction on agar plates.C. albicanswas the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimentalD23°Cvalues forBacillus subtilis,Bacillus pumilus,Bacillus atrophaeus, andGeobacillus stearothermophiluswere determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times (Dvalues) are distinctly lower thanDvalues obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma.
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Feng, Ling, Céline Peillex-Delphe, Changwei Lü, Da Wang, Stefanos Giannakis und Cesar Pulgarin. „Employing bacterial mutations for the elucidation of photo-Fenton disinfection: Focus on the intracellular and extracellular inactivation mechanisms induced by UVA and H2O2“. Water Research 182 (September 2020): 116049. http://dx.doi.org/10.1016/j.watres.2020.116049.
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Liang, Jialiang, Fuyang Liu, Mian Li, Wen Liu und Meiping Tong. „Facile synthesis of magnetic Fe3O4@BiOI@AgI for water decontamination with visible light irradiation: Different mechanisms for different organic pollutants degradation and bacterial disinfection“. Water Research 137 (Juni 2018): 120–29. http://dx.doi.org/10.1016/j.watres.2018.03.027.
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Carrascosa, Conrado, Dele Raheem, Fernando Ramos, Ariana Saraiva und António Raposo. „Microbial Biofilms in the Food Industry—A Comprehensive Review“. International Journal of Environmental Research and Public Health 18, Nr. 4 (19.02.2021): 2014. http://dx.doi.org/10.3390/ijerph18042014.
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Biofilms, present as microorganisms and surviving on surfaces, can increase food cross-contamination, leading to changes in the food industry’s cleaning and disinfection dynamics. Biofilm is an association of microorganisms that is irreversibly linked with a surface, contained in an extracellular polymeric substance matrix, which poses a formidable challenge for food industries. To avoid biofilms from forming, and to eliminate them from reversible attachment and irreversible stages, where attached microorganisms improve surface adhesion, a strong disinfectant is required to eliminate bacterial attachments. This review paper tackles biofilm problems from all perspectives, including biofilm-forming pathogens in the food industry, disinfectant resistance of biofilm, and identification methods. As biofilms are largely responsible for food spoilage and outbreaks, they are also considered responsible for damage to food processing equipment. Hence the need to gain good knowledge about all of the factors favouring their development or growth, such as the attachment surface, food matrix components, environmental conditions, the bacterial cells involved, and electrostatic charging of surfaces. Overall, this review study shows the real threat of biofilms in the food industry due to the resistance of disinfectants and the mechanisms developed for their survival, including the intercellular signalling system, the cyclic nucleotide second messenger, and biofilm-associated proteins.
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KU, KUO-LONG, JUI-LONG CHIOU, FANG-CHI LIU und ROBIN Y. Y. CHIOU. „Advanced Gas Chromatographic–Mass Spectrometric Studies for Identification of the Cellular Octadecenoate Isomers and Changes of Fatty Acid Composition Induced by Ethanol Stress in Escherichia coli and Escherichia coli O157:H7“. Journal of Food Protection 70, Nr. 3 (01.03.2007): 616–22. http://dx.doi.org/10.4315/0362-028x-70.3.616.
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Ethanol can be introduced to foods of various origins and is commonly used for surface disinfection. Low concentrations of residual ethanol may provide an opportunity for pathogens to adapt and grow. Change of cellular fatty acid composition is one of adaptation mechanisms enabling bacteria to grow under varied stresses. Since instrumental analyses of bacterial octadecenoate isomers are sophisticated, gas chromatographic analyses of the isomers, namely trans-9-octadecenoate, trans-11-octadecenoate, cis-9-octadecenoate, and cis-11-octadecenoate, and ethanol-induced formation of trans-9-octadecenoate in Escherichia coli and E. coli O157:H7 were intensively investigated. When an HP-1, a nonpolar capillary column, was used for gas chromatographic analyses of 28 authentic bacterial acid methyl esters, resolution was satisfied for all fatty acid components except trans-9-octadecenoate and cis-11-octadecenoate, being overlapped. When the column was replaced by an RTx-2330, a polar capillary column, all of the above-mentioned octadecenoate isomers were resolved. When cells of E. coli and E. coli O157:H7 were harvested after submerged cultivation (30°C, 150 rpm) in tryptic soy broth and tryptic soy broth supplemented with 5% ethanol at early stationary phase and subjected to cellular fatty acid analyses by using an HP-1 and RTx-2330 coupled with a mass detector, 12 fatty acids, i.e., trans-9-octadecenoate, 5 saturated fatty acids, 2 cyclopropane fatty acids and 4 cisunsaturated fatty acids, were identified. Individual fatty acid contents varied depending on nature of fatty acid, strain of E. coli, and supplement of ethanol. As affected by ethanol stress for both E. coli strains, contents of trans-9-octadecenoate increased, whereas contents of cyc-9,10-methylene octadecanoate (cyc-9,10-19:0) decreased significantly (P < 0.05). Apparently, both E. coli strains have rendered necessary fatty acid adaptation to survive and grow under ethanol stress.
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Yao, Sai, Xingzhong Yuan, Longbo Jiang, Ting Xiong und Jin Zhang. „Recent Progress on Fullerene-Based Materials: Synthesis, Properties, Modifications, and Photocatalytic Applications“. Materials 13, Nr. 13 (30.06.2020): 2924. http://dx.doi.org/10.3390/ma13132924.
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Solar light is an inexpensive energy source making up for energy shortage and solving serious environmental problems. For efficient utilization of solar energy, photocatalytic materials have attracted extensive attention over the last decades. As zero-dimensional carbon nanomaterials, fullerenes (C60, C70, etc.) have been extensively investigated for photocatalytic applications. Due to their unique properties, fullerenes can be used with other semiconductors as photocatalyst enhancers, and also as novel photocatalysts after being dispersed on non-semiconductors. This review summarizes fullerene-based materials (including fullerene/semiconductors and fullerene/non-semiconductors) for photocatalytic applications, such as water splitting, Cr (VI) reduction, pollutant degradation and bacterial disinfection. Firstly, the optical and electronic properties of fullerene are presented. Then, recent advances in the synthesis and photocatalytic mechanisms of fullerene-based photocatalysts are summarized. Furthermore, the effective performances of fullerene-based photocatalysts are discussed, mainly concerning photocatalytic H2 generation and pollutant removal. Finally, the current challenges and prospects of fullerene-based photocatalysts are proposed. It is expected that this review could bring a better understanding of fullerene-based photocatalysts for water treatment and environmental protection.
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Brissaud, F., P. Xu und M. Auset. „Extensive reclamation technologies, assets for the development of water reuse in the Mediterranean“. Water Supply 3, Nr. 4 (01.08.2003): 209–16. http://dx.doi.org/10.2166/ws.2003.0064.
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In the Mediterranean, the main water reuse application is and will long remain irrigation. Irrigation of public parks, landscape, golf courses, market gardening and orchards is expected to develop rapidly. Such uses require the microbial decontamination of reclaimed wastewater. Extensive reclamation technologies are well adapted to the Mediterranean context for their easy and cost effective O&M; however their ability to reliably meet health related standards have been questioned. The paper reviews the main factors of variations in the bacterial abatement provided by extensive treatment techniques - stabilisation reservoirs, ponds and infiltration percolation. Thanks to advances in the knowledge and modelling of disinfection mechanisms, the predictability of microbial decontamination by extensive technologies is being significantly improved; the development of better design tools leading to reliable treatments is foreseen. However, due to limitations in the microbial removal, extensive techniques cannot meet highly conservative requirements. Extensive techniques will play an important part in the development of water reuse and fresh water savings in the Mediterranean as far as water quality standards only aim at limiting health risks to an acceptable level.
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Wang, Wanjun, Lizhi Zhang, Taicheng An, Guiying Li, Ho-Yin Yip und Po-Keung Wong. „Comparative study of visible-light-driven photocatalytic mechanisms of dye decolorization and bacterial disinfection by B–Ni-codoped TiO2 microspheres: The role of different reactive species“. Applied Catalysis B: Environmental 108-109 (Oktober 2011): 108–16. http://dx.doi.org/10.1016/j.apcatb.2011.08.015.
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Clement, Julia L., und Penelope S. Jarrett. „Antibacterial Silver“. Metal-Based Drugs 1, Nr. 5-6 (01.01.1994): 467–82. http://dx.doi.org/10.1155/mbd.1994.467.
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The antibacterial activity of silver has long been known and has found a variety of applications because its toxicity to human cells is considerably lower than to bacteria. The most widely documented uses are prophylactic treatment of burns and water disinfection. However, the mechanisms by which silver kills cells are not known. Information on resistance mechanisms is apparently contradictory and even the chemistry of Ag+ in such systems is poorly understood.Silver binds to many cellular components, with membrane components probably being more important than nucleic acids. It is difficult to know whether strong binding reflects toxicity or detoxification: some sensitive bacterial strains have been reported as accumulating more silver than the corresponding resistant strain, in others the reverse apparently occurs. In several cases resistance has been shown to be plasmid mediated. The plasmids are reported as difficult to transfer, and can also be difficult to maintain, as we too have found. Attempts to find biochemical differences between resistant and sensitive strains have met with limited success: differences are subtle, such as increased cell surface hydrophobicity in a resistant Escherichia coli.Some of the problems are due to defining conditions in which resistance can be observed. Silver(I) has been shown to bind to components of cell culture media, and the presence of chloride is necessary to demonstrate resistance. The form of silver used must also be considered. This is usually water soluble AgNO3, which readily precipitates as AgCl. The clinically preferred compound is the highly insoluble silver sulfadiazine, which does not cause hypochloraemia in burns. It has been suggested that resistant bacteria are those unable to bind Ag+ more tightly than does chloride. It may be that certain forms of insoluble silver are taken up by cells, as has been found for nickel. Under our experimental conditions, silver complexed by certain ligands is more cytotoxic than AgNO3, yet with related ligands is considerably less toxic. There is evidently a subtle interplay of solubility and stability which should reward further investigation.
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Ivanovska, Aleksandra, Sonja Veljović, Biljana Dojčinović, Nenad Tadić, Katarina Mihajlovski, Maja Natić und Mirjana Kostić. „A Strategy to Revalue a Wood Waste for Simultaneous Cadmium Removal and Wastewater Disinfection“. Adsorption Science & Technology 2021 (12.08.2021): 1–14. http://dx.doi.org/10.1155/2021/3552300.
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In this investigation, the possibility of wood waste (hardwoods such as oaks’ and alternatives’ staves from Balkan cooperage) revalorization for simultaneous cadmium removal and wastewater disinfection was examined. All samples were characterized in terms of their crystallinity index and crystallite size, amount of functional groups, and surface chemistry (determined by ATR-FTIR) as well as antibacterial activity. Mulberry is characterized by the lowest crystallinity index which can be ascribed to the highest crystallite size disabling crystallite denser packaging, while myrobalan plum has about 23% lower crystallite size that enables crystallite better packaging, thus resulting in a 42.4% higher crystallinity index compared to the mulberry. All oaks have a significantly higher amount of carboxyl groups compared to the alternatives (0.23-0.28 vs. 0.12-0.19 mmol/g). The adsorption experiments revealed that with increasing the initial cadmium concentration from 15 up to 55 mg/g, samples’ adsorption capacity increases by 89-220%. The equilibrium data fit well with the Langmuir isotherm model implying monolayer coverage of cadmium ions over a homogeneous wood surface. The relationship between the samples’ maximum adsorption capacities (ranged from 5.726 to 12.618 mg/g), their crystallinity index, and crystallite size was established. According to ATR-FTIR spectra, aldehyde, carboxyl, hydroxyl, and phenyl groups present on the wood waste surface are involved in Cd2+ adsorption which proceeds via the interplay of the complexation, cation-π interactions, and ion-exchange mechanisms. Mulberry and myrobalan plum showed about 89% and 80% of the total uptake capacity of cadmium within 60 min, while the equilibrium was attained after 240 min of contact time. Good compliance with pseudo-second kinetic order indicated that cadmium adsorption was mediated by chemical forces. Thermodynamic parameters revealed the spontaneous and exothermic character of cadmium ion adsorption onto mulberry and myrobalan plum. All studied samples provide maximum bacterial reduction (>99%) for E. coli and S. aureus. Wood waste from Balkan cooperage can be successfully used for simultaneous cadmium removal and wastewater disinfection.
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Harvey, Michelle L., Ian R. Dadour und Natalie E. Gasz. „Maggot Therapy in Chronic Wounds: New Approaches to Historical Practices“. Annals of the Entomological Society of America 114, Nr. 4 (01.04.2021): 415–24. http://dx.doi.org/10.1093/aesa/saab012.
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Abstract Blowfly larvae of Lucilia sericata (Meigen) (Diptera: Calliphoridae) are well established as debridement agents in nonhealing wounds. Maggot therapy (MT) experienced reduced application following adoption of Penicillin and other antibiotics, but the advent of antibiotic resistance and the growing global wound burden have boosted demand for new therapies. The mechanisms of action are well accepted, with debridement, disinfection, biofilm destruction, and inhibition, as well as the stimulation of tissue growth uniformly acknowledged as a remarkable biotherapy. The mechanisms of action, while well-recognized, are still being examined. The efforts to understand isolated aspects of a complex system, have resulted in a tendency to approach the field from simplified viewpoints that remove the holistic system of the larvae. Furthermore, clinical studies have conflated wound debridement and healing in definitions of ‘success’. Thus, both in vitro and clinical studies have reported mixed results, presenting some uncertainty regarding the utility of MT that prohibits routine clinical adoption. This review builds from the generally accepted basic mechanisms to justify a future for MT that encompasses larval-bacterial symbioses as the basis to a holistic system. Symbioses are well documented in the Insecta, and literature in MT supports the existence of established symbiotic associations that provide enhanced debridement action. The future of MT requires consideration of a biological system that confers enhanced antimicrobial action on larvae when selective pre-exposure to carefully selected symbionts is adopted. In treating contemporary infections, there is much to be gained from reflecting on the natural biology of the organism, as MT was used with success long before we sterilized the system.
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Wyczarska-Kokot, Joanna, Edyta Łaskawiec und Florian Piechurski. „An Evaluation of the Effectiveness of Nanosilver in Swimming Pool Water Treatment - Water Quality and Toxicity of the Product“. Ecological Chemistry and Engineering S 27, Nr. 1 (01.03.2020): 113–27. http://dx.doi.org/10.2478/eces-2020-0007.
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AbstractThe possibility of applying a colloidal solution of nanosilver in the closed circuit of pool water treatment as a complementary disinfectant with chlorine compounds was presented. The applied nanosilver solution is characterized, by hygienic certificate, as having a very high biocidal effect. Samples of pool water for the control were taken from 5 points of a pool circuit. The safety of the water was appraised by comparing the bacteriological and physicochemical test results with the admissible values specified by hygienic requirements. The results show that nanosilver solution can be successfully applied for precoating the filter bed and supporting the disinfection system. Special attention was paid to the bacteriological purity and stability of the disinfectant concentration. The influence of concentration of colloidal nanosilver (0-25 mg/dm3) on bacterial bioluminescence, crustacean mortality and macroscopic effect of root growth and seed germination of selected plants was analysed. The results obtained were related to the current knowledge on the impact of nanoparticles on indicator organisms. It was found that due to many still unknown mechanisms of interaction and transformation of nanoparticles in living organisms, further study of this issue is necessary.
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Alsaedi, Mossab K., Ghada K. Alothman, Mohammed N. Alnajrani, Omar A. Alsager, Sultan A. Alshmimri, Majed A. Alharbi, Majed O. Alawad, Shahad Alhadlaq und Seetah Alharbi. „Antibiotic Adsorption by Metal-Organic Framework (UiO-66): A Comprehensive Kinetic, Thermodynamic, and Mechanistic Study“. Antibiotics 9, Nr. 10 (21.10.2020): 722. http://dx.doi.org/10.3390/antibiotics9100722.
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Bacterial antibiotic resistance has been deemed one of the largest modern threats to human health. One of the root causes of antibiotic resistance is the inability of traditional wastewater management techniques, such as filtration and disinfection, to completely eliminate residual antibiotics from domestic and industrial effluents. In this study, we examine the ability of UiO-66; a metal-organic framework (MOF); in removing the antibiotic Doxycycline from aqueous environments. This study’s findings suggest that UiO-66 was able to remove nearly 90% of the initial Doxycycline concentration. To correlate the isothermal data, Langmuir and Freundlich models were used. It was determined that the Langmuir model was best suited. Pseudo-first and -second order models were examined for kinetic data, where the pseudo-second order model was best suited—consistent with the maximum theoretical adsorption capacity found by the Langumir model. Thermodynamic analysis was also examined by studying UiO-66 adsorption under different temperatures. Mechanisms of adsorption were also analyzed through measuring adsorption at varying pH levels, thermogravimetric analysis (TGA), Infrared spectroscopy (IR) and Brunauer–Emmet–Teller (BET). This study also explores the possibility of recycling MOFs through exposure to gamma radiation, heat, and heating under low pressure, in order for UiO-66 to be used in multiple, consecutive cycles of Doxycycline removal.
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Calle, Alexandra, Mariana Fernandez, Brayan Montoya, Marcelo Schmidt und Jonathan Thompson. „UV-C LED Irradiation Reduces Salmonella on Chicken and Food Contact Surfaces“. Foods 10, Nr. 7 (24.06.2021): 1459. http://dx.doi.org/10.3390/foods10071459.
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Ultraviolet (UV-C) light-emitting diode (LED) light at a wavelength of 250–280 nm was used to disinfect skinless chicken breast (CB), stainless steel (SS) and high-density polyethylene (HD) inoculated with Salmonella enterica. Irradiances of 2 mW/cm2 (50%) or 4 mW/cm2 (100%) were used to treat samples at different exposure times. Chicken samples had the lowest Salmonella reduction with 1.02 and 1.78 Log CFU/cm2 (p ≤ 0.05) after 60 and 900 s, respectively at 50% irradiance. Higher reductions on CB were obtained with 100% illumination after 900 s (>3.0 Log CFU/cm2). Salmonella on SS was reduced by 1.97 and 3.48 Log CFU/cm2 after 60 s of treatment with 50% and 100% irradiance, respectively. HD showed a lower decrease of Salmonella, but still statistically significant (p ≤ 0.05), with 1.25 and 1.77 Log CFU/cm2 destruction for 50 and 100% irradiance after 60 s, respectively. Longer exposure times of HD to UV-C yielded up to 99.999% (5.0 Log CFU/cm2) reduction of Salmonella with both irradiance levels. While UV-C LED treatment was found effective to control Salmonella on chicken and food contact surfaces, we propose three mechanisms contributing to reduced efficacy of disinfection: bacterial aggregation, harboring in food and work surface pores and light absorption by fluids associated with CB.
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Singh, Raj Kamal, Ligy Philip und Sarathi Ramanujam. „Disinfection of water by pulsed power technique: a mechanistic perspective“. RSC Advances 6, Nr. 15 (2016): 11980–90. http://dx.doi.org/10.1039/c5ra26941e.
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KHAN, ADNAN, und MUDASSAR IMRAN. „OPTIMAL DOSING STRATEGIES AGAINST SUSCEPTIBLE AND RESISTANT BACTERIA“. Journal of Biological Systems 26, Nr. 01 (März 2018): 41–58. http://dx.doi.org/10.1142/s0218339018500031.
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Mathematical models can be very useful in determining efficient and successful antibiotic dosing techniques against bacterial infections. There are several challenging issues involved, the presence of drug resistant bacteria being one. Recent rise in antibiotic resistant strains of bacteria is a grave public health hazard, hence there is a need to develop dosing protocols taking into account the presence of these resistant strains. In this study, we consider a model for antibiotic treatment of a bacterial infection where the bacteria are divided into two sub-populations: susceptible and resistant. The mechanism of acquisition of resistance by the susceptible bacteria considered is via the process of conjugation. We find the steady-state solutions under an antibiotic protocol of discrete periodic doses and analyze their stability. We also prove an extension of a result that pertains to the persistence of bacteria. In addition, we perform the bifurcation analysis under this dosing protocol and show that bi-stability exists for the bacterial population. Furthermore, efficient treatment strategies are devised that ensure bacterial elimination while minimizing the quantity of antibiotic used. Such treatments are necessary to decrease the chances of further development of resistance in bacteria and to minimize the overall treatment cost. We consider the cases of varying antibiotic costs, different initial bacterial densities and bacterial attachment to solid surfaces, and obtain the optimal strategies for all the cases. The results show that the optimal treatments ensure disinfection for a wide range of scenarios.
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Gupta, Rimzhim, Jayant M. Modak und Giridhar Madras. „Behavioral analysis of simultaneous photo-electro-catalytic degradation of antibiotic resistant E. coli and antibiotic via ZnO/CuI: a kinetic and mechanistic study“. Nanoscale Advances 1, Nr. 10 (2019): 3992–4008. http://dx.doi.org/10.1039/c9na00483a.
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Lackmann, Jan-Wilm, Simon Schneider, Eugen Edengeiser, Fabian Jarzina, Steffen Brinckmann, Elena Steinborn, Martina Havenith, Jan Benedikt und Julia E. Bandow. „Photons and particles emitted from cold atmospheric-pressure plasma inactivate bacteria and biomolecules independently and synergistically“. Journal of The Royal Society Interface 10, Nr. 89 (06.12.2013): 20130591. http://dx.doi.org/10.1098/rsif.2013.0591.
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Cold atmospheric-pressure plasmas are currently in use in medicine as surgical tools and are being evaluated for new applications, including wound treatment and cosmetic care. The disinfecting properties of plasmas are of particular interest, given the threat of antibiotic resistance to modern medicine. Plasma effluents comprise (V)UV photons and various reactive particles, such as accelerated ions and radicals, that modify biomolecules; however, a full understanding of the molecular mechanisms that underlie plasma-based disinfection has been lacking. Here, we investigate the antibacterial mechanisms of plasma, including the separate, additive and synergistic effects of plasma-generated (V)UV photons and particles at the cellular and molecular levels. Using scanning electron microscopy, we show that plasma-emitted particles cause physical damage to the cell envelope, whereas UV radiation does not. The lethal effects of the plasma effluent exceed the zone of physical damage. We demonstrate that both plasma-generated particles and (V)UV photons modify DNA nucleobases. The particles also induce breaks in the DNA backbone. The plasma effluent, and particularly the plasma-generated particles, also rapidly inactivate proteins in the cellular milieu. Thus, in addition to physical damage to the cellular envelope, modifications to DNA and proteins contribute to the bactericidal properties of cold atmospheric-pressure plasma.
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Dinh, Ngo Xuan, Nguyen Van Quy, Tran Quang Huy und Anh-Tuan Le. „Decoration of Silver Nanoparticles on Multiwalled Carbon Nanotubes: Antibacterial Mechanism and Ultrastructural Analysis“. Journal of Nanomaterials 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/814379.
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Recently, development of carbon nanocomposites composed of carbon nanostructures and metal nanoparticles has attracted much interests because of their large potential for technological applications such as catalyst, sensor, biomedicine, and disinfection. In this work, we established a simple chemistry method to synthesize multiwalled carbon nanotubes (MWCNTs) decorated with silver nanoparticles (Ag-NPs) using a modified photochemical reaction (Tollens process). The formation and interaction of Ag-NPs with functionalized groups on the surface of MWCNTs were analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the MWCNTs was approximately ~7 nm with nearly uniform size distribution. Antibacterial effect of Ag-MWCNTs nanocomposites was evaluated against two pathogenic bacteria including Gram-negativeEscherichia Coliand Gram-positiveStaphylococcus aureusbacteria. Interaction and bactericidal mechanism of Ag-MWCNTs with tested bacteria was studied by adapting the electron microscopy. Analysis on ultrastructural changes of bacterial cells indicates that antibacterial action mechanism of Ag-MWCNTs is physical interaction with cell membrane, the large formation of cell-Ag-MWCNTs aggregates, and faster destructibility of cell membrane and disruption of membrane function, hence resulting in cells death.
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Wang, Wanjun, Guocheng Huang, Jimmy C. Yu und Po Keung Wong. „Advances in photocatalytic disinfection of bacteria: Development of photocatalysts and mechanisms“. Journal of Environmental Sciences 34 (August 2015): 232–47. http://dx.doi.org/10.1016/j.jes.2015.05.003.
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Huo, Zheng-Yang, Guo-Qiang Li, Tong Yu, Yun Lu, Hao Sun, Yin-Hu Wu, Cecilia Yu, Xing Xie und Hong-Ying Hu. „Impact of water quality parameters on bacteria inactivation by low-voltage electroporation: mechanism and control“. Environmental Science: Water Research & Technology 4, Nr. 6 (2018): 872–81. http://dx.doi.org/10.1039/c8ew00041g.
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Zhang, Ling Ling, Su Qin Li, Xiao Ming Liu, Da Qiang Cang und Yu Long Ding. „Disinfection of Water and Wastewater Using ZnO Nanofluids - Effect of Shaking Speed of Incubator“. Advanced Materials Research 183-185 (Januar 2011): 2298–302. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.2298.
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Nanofluids are liquids containing nanoparticles, nanotube or nanowire suspensions. This work investigates the disinfection properties of ZnO nanofluids, especially the change of ZnO disinfection properties when facing different shaking speeds of incubator (50rpm, 100rpm, 200rpm and 300rpm). In this work, E. coli was used as model bacteria to test the disinfection property of ZnO nanofluids. Plant counting method was used to examine the number of bacteria before and after the treatment of ZnO nanofluids. The results demonstrate that both ZnO nanofluids sample A and B could inhibit or kill E. coli bacteria. ZnO sample B with smaller particle size showed better antimicrobial activities. Treated with higher concentration of ZnO sample B exhibited better antimicrobial activities. Besides, this work also demonstrated that with higher shaking speed of incubator, ZnO nanofluids showed better antimicrobial activities. The antimicrobial mechanism is thought to be associated with physical interaction between ZnO particles and the biological cells and enhanced mass transfer of possible chemical species produced due to the presence of ZnO particles.
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Lee, Lawrence H., Adam J. Arnold, Cutberto A. Santillan, Monica B. Emelko, Sarah E. Dickson und Jen-Shih Chang. „Bench-Scale Disinfection of Bacteria and Viruses with Pulsed Arc Electrohydraulic Discharge“. Water Quality Research Journal 43, Nr. 1 (01.02.2008): 77–84. http://dx.doi.org/10.2166/wqrj.2008.010.
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Abstract Pulsed arc electrohydraulic discharge (PAED) offers concurrent treatment of chemical and microbial target compounds in water by several mechanisms. Here, Escherichia coli, Bacillus subtilis spore, and MS2 bacteriophage inactivation by PAED were investigated using two bench-scale reactors (0.7 and 3 L). A plasma channel was created between a pair of iron electrodes set 0.5 mm apart in these reactors. Pulsed applied voltage was supplied at approximately 0.3 kJ/pulse (~100 µsec). In the 0.7-L reactor, median E. coli, B. subtilis, and MS2 reductions of 2.4-, 4.6-, and 3.7-log, respectively, were observed after approximately 80 seconds of treatment in water with a conductivity of 14.7 mS; reductions of 2.8-, 4.0-, and 3.7-log, respectively, were observed in treated drinking water filter effluent (conductivity of 610 µS). In the 3-L reactor, at a conductivity of 500 to 600 µS, 1.9- and approximately 0.9-log median reductions of E. coli and B. subtilis were achieved after 500 pulses (~3,300 sec); and, at a conductivity of 4.3 mS, median E. coli reductions of 0.5-log were achieved after 50 pulses (400 sec). Further work is necessary to elucidate the primary mechanism(s) of disinfection acting in the PAED system and how they relate to the reactor design, applied power requirements, and disinfection of specific target microorganisms.
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Schaefer, Charles E., Graig M. Lavorgna, Todd S. Webster, Marc A. Deshusses, Christina Andaya und Ana Urtiaga. „Pilot-scale electrochemical disinfection of surface water: assessing disinfection by-product and free chlorine formation“. Water Supply 17, Nr. 2 (26.09.2016): 526–36. http://dx.doi.org/10.2166/ws.2016.165.
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Electrochemical disinfection of surface water using mixed metal oxide anodes was evaluated in a pilot-scale demonstration. Disinfection rates, chlorine generation, energy demand, and generation of disinfection by-products were monitored over the 190-day study. Particular attention was given to the generation of trihalomethanes (THMs) and haloacetic acids (HAAs) during the electrochemical treatment cycle. In addition, the potential for generation of THMs and HAAs during post-treatment storage of the water was assessed. The electrochemical treatment system resulted in a 2- to 3-log removal of total heterotrophic bacteria, with values below detection (<1 CFU/mL) often observed. Disinfection occurred with only very low levels of observed chlorine generation (<0.1 mg/L), suggesting that alternate disinfection mechanisms likely played a significant role in the observed removal of bacteria. THM and HAA concentrations after treatment were consistently well below regulatory levels. Results also showed that electrochemical treatment significantly reduced the formation of bromoform when the water received subsequent exposure to hypochlorite. Removal of naturally occurring bromide in the water by the electrochemical system may have been the cause (in part) for this observed mitigation of bromoform formation. The formation of calcium scale on the cathode surface over time was the primary operational challenge.
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Fan, Xin, Fan Yang, Chuanxiong Nie, Lang Ma, Chong Cheng und Rainer Haag. „Biocatalytic Nanomaterials: A New Pathway for Bacterial Disinfection“. Advanced Materials 33, Nr. 33 (03.07.2021): 2100637. http://dx.doi.org/10.1002/adma.202100637.
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