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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
511

Effective Control of Antibiotic Resistance in Cheese and Characterization of a Dairy Enterococcus faecium Isolate Carrying a Persistent, TA-independent Tetracycline Resistance-encoding Plasmid

Li, Xinhui 08 September 2011 (has links)
No description available.
512

Indicative Bacteria in Stored Biosolids and Wastewater Associated Pharmaceuticals in the Environment

Wu, Chenxi 08 September 2010 (has links)
No description available.
513

Reducering av antibiotikarester i akvatiskamiljöer : Alternativa behandlingsmetoder och vattenreningstekniker

Eriksson, Karin, Lindströn, Moa January 2022 (has links)
Antibiotikaresistens är en av de största globala utmaningarna i sjukvården och om den mängdantibiotika som används idag fortsätter att användas i framtiden riskerar det att kosta 10 miljonermänniskor om livet varje år från år 2050. Antibiotikarester i akvatiska miljöer ökar risken förspridning av antibiotikaresistenta bakterier. Vissa antibiotikum är även toxiska för vattenlevandeorganismer. Dagens vattenreningsverk är inte utformade att rena vatten från antibiotikaresteroch därför följer resterna med vattnet ut i recipienten. För att lösa det här problemet behövervattenreningsverk utvecklas med nya reningsmetoder för att kunna rena antibiotika och vårdenmåste minska användandet i sjukvården. De kopplade globala målen kopplade till detta problemär mål 3 “God hälsa och välbefinnande”, 6 “rent vatten och sanitet”, 11 “hållbara städer ochsamhällen”, 14 “hav och marina resurser” (Globala målen, 2021a; Globala målen, 2021b;Globala målen, 2021c; Globala målen, 2021d). Arbetet undersöker potentiella lösningar förutveckling av vattenreningsverk och alternativa behandlingsmetoder för att minska användandetav antibiotika inom sjukvården. För att göra detta har intervjuer med respondenter på Gävlesjukhus och Duvbackens reningsverk genomförts för att hitta brister i dagens teknik.Förbättringsförslagen är baserade på vetenskapliga artiklar och myndigheters hemsidor. I EUfinns det inga krav gällande att producenterna av läkemedel ska granska den verkligamiljöpåverkan läkemedlet har efter att det har godkänts för försäljning. Antibiotikaläkemedel ärbiologiskt aktiva föreningar vilka, även i små mängder, kan påverka det akvatiska ekosystemetnegativt. Penicillin är det vanligaste använda antibiotikan i Gävles sluten- och primärvård.Slutenvården utgör den största gruppen av antibiotikaanvändare men beaktas bör att det är okänthuruvida dessa användare tidigare kommer från primärvården. Det är också okänt hur stor andelav inköpta läkemedel som faktiskt använts. De reningstekniker bäst lämpade att använda påvattenreningsverk för att rena antibiotikarester varierar och beror bland annat på klimat,resurser och vilken typ av antibiotika som finns i avloppsvattnet. Ozonering är positivt eftersomdet är effektivt mot antibiotikasubstanser med brett spektrum. Det ger heller inte någonpåverkan på slam från vattenreningsverket eftersom ozonet löses upp och blir till syre efterreningen. Ozonering är ofta mest effektiv i kombination med andra reningstekniker vilket kallasför hybridprocesser. Adsorption är effektivt för rening av antibiotikarester och den vanligametoden kolbaserad adsorption är effektiv vid rening av tetracyklinrester. Metoden är effektiveftersom det tar upp mycket av resterna samt att energikostnaden är låg. Sandfilter är en brametod för att rena bort antibiotikaresistenta bakterier och dessutom renar filtrets adsorptionockså rester av tetracyklin. Genom att införa en reningsteknik kombinerad med aktivt kol ochozonering för att rena antibiotikarester från avloppsvattnet samt att använda vakuumassisteradsårbehandling kan användandet av antibiotika minska. / Antibiotic resistance is one of the biggest global challenges in modern day healthcare and ifcontinued use of antibiotics in the same amount as today, it will kill 10 million people every yeararound 2050. Antibiotic residues in aquatic environments increase the risk of spreading ofspreading antibiotic resistant bacteria. Some antibiotics are also toxic to aquatic organisms.Because the wastewater plants are not designed to purify the water from antibiotics the residuescontinue with the water to the recipient. To solve the problem the wastewater plants needs toupgrade with new technology and the healthcare industry reduces the amount prescribedantibiotics. The UN global goals connected to this issue is goal 3 “Good health and well-being”,6 “clean water and sanitary”, 11 “sustainable cities and communities” and 14 “life below water”(Global goals). This study explores potential developments in the wastewater plants andalternatives for antibiotics in healthcare by interviewing respondents at the hospital in Gävle andthe wastewater plant Duvbacken to find the deficiencies of today. Included suggestions are basedon scientific articles and Swedish agencies. There is no requirement for the medicalmanufacturers within the EU to examine the environmental impact of medicines after they havebeen approved for sale. Antibiotic drugs are biologically active compounds which, even in smallamounts, can adversely affect the aquatic ecosystem. Penicillin is the most widely used antibioticin Gävle's inpatient and outpatient care. Outpatient care constitutes the largest group ofantibiotic users, but it should be taken into account that people from this group may havepreviously belonged to inpatient care. It is also unknown how much of each purchased drug thatis used. The treatment techniques that are best suited to use at water treatment plants to purifyantibiotic residues vary and depend on the climate, resources and the type of antibiotics found inthe wastewater. Ozonation is positive as it is effective for broad spectrum antibiotics. It also hasno effect on sludge from the water treatment plant because the ozone dissolves and becomesoxygen after the treatment. Ozonation is often most effective when combined with otherpurification techniques which is called hybrid processes. Adsorption is effective for thepurification of antibiotic residues and the usual method of carbon-based adsorption is effective inthe purification of tetracycline residues. The method is effective because it absorbs much of theresidues at a low energy cost. Sand filter is an effective method to clean away antibiotic-resistantbacteria and in addition, the adsorption of the filter also cleans residues of tetracycline. Byintroducing a purification technique combined with activated carbon and ozonation to purify thewastewater in wastewater plants and to use vacuum assisted wound treatment, the use ofantibiotics can be reduced.
514

Profiling of Microbial Communities, Antibiotic Resistance, Functional Genes, and Biodegradable Dissolved Organic Carbon in a Carbon-Based Potable Water Reuse System

Blair, Matthew Forrest 17 March 2023 (has links)
Water reuse has become a promising alternative to alleviate stress on conventional freshwater resources in the face of population growth, sea level rise, source water depletion, eutrophication of water bodies, and climate change. Potable water reuse intentionally looks to purify wastewater effluent to drinking water quality or better through the development and implementation of advanced treatment trains. While membrane-based treatment has become a widely-adopted treatment step to meet this purpose, there is growing interest in implementing treatment trains that harness microorganisms as a more sustainable and less energy-intensive means of removing contaminants of emerging concern (CECs), through biological degradation or transformation. In this dissertation, various aspects of the operation of a microbially-active carbon-based advanced treatment train producing water intended for potable reuse are examined, including fate of dissolved organic carbon, underlying microbial populations, and functional genes are explored. Further, dynamics associated with antibiotic resistance genes (ARGs), identified as a microbially-relevant CECs, are also assessed. Overall, this dissertation advances understanding associated with the interplay between and within treatment processes as they relate to removal of various organic carbon fractions, microbially community dynamics, functional genes, and ARGs. Further, when relevant, these insights are contextualized to operational conditions, process upsets, water quality parameters, and other intended water uses within the water industry with the goal of broadening the application of advanced molecular tools beyond the scope of academic research. Specifically, this dissertation illuminates relationships among organic carbon fractions and molecular markers within an advanced treatment train employing flocculation, coagulation, and sedimentation (FlocSed), ozonation, biologically active carbon (BAC) filtration, granular active carbon (GAC) contacting, and UV disinfection. Biodegradable dissolved organic carbon (BDOC) analysis was adapted specifically as an assay relevant to assessing dissolved organic carbon biodegradability by BAC/GAC-biofilms and applied to profile biodegradable/non-biodegradable organic carbon as wastewater effluent passed through each of these treatment stages. Of particular interest was the role of ozonation in producing bioavailable organic carbon that can be effectively removed by BAC filtration. In addition to understanding the removal of fractionalized organic carbon, next generation DNA sequencing technologies (NGS) were utilized to better understand the microbial dynamics characteristic of complex microbial communities during disinfection and biological treatment. Specifically, this analysis was focused on succession and colonization of taxa, genes related to a wide range of functional interests (e.g. metabolic processes, horizontal gene transfer, DNA repair, and nitrogen cycling), and microbial CECs. Finally, NGS technologies were employed to assess the differences between a wide range of water use categories, including conventional drinking water, potable reuse, and non-potable reuse effluent's microbiomes to identify core and discriminatory taxa associated with intended water usage. The outcomes of this dissertation provide valuable information for optimizing carbon-based treatment trains as an alternative to membrane-based treatment for sustainable water reuse and also advance the application of NGS as a diagnostic tool for assessing the efficacy of various water treatment technologies for achieving treatment goals. / Doctor of Philosophy / Several factors have led to increased stress on conventional drinking water sources and widespread global water scarcity. Projections indicate that continued population growth, increased water demand, and degradation of current freshwater resources will negatively contribute to water needs and underscore the need to secure new potable (i.e. fit for human consumption) sources. Water reuse is a promising alternative to offset the growing demands on traditional potable sources and ameliorate negative consequences associated with water scarcity. Discharge of treated wastewater to marine environments is especially a lost opportunity, as the water will no longer be of value to freshwater habitats or as a drinking water source. Water reuse challenges the conventional wastewater treatment paradigm by providing advanced treatment of wastewater effluent to produce a valuable resource that can be safely used directly for either non-potable (e.g., irrigation, firefighting) or potable (i.e., drinking water) applications. The means of achieving advanced treatment of wastewater effluents can take many forms, commonly relying on the utilization of membrane filtration. However, membrane filtration is an intensive process and suffers from high initial costs, high operational costs, membrane fouling with time, and the production of a salty and difficult to dispose of waste stream. These drawbacks have motivated the water reuse industry to explore more sustainable approaches to achieving high quality effluents. One such alternative relies on the utilization of microorganisms to provide biological degradation and transformation of contaminants through a process known as biologically active filtration (BAF). Comparatively to membrane systems, BAF is more cost effective and produces significantly fewer byproducts while still producing high quality treated water for reuse. However, the range in quality of the resulting treated water has not yet been fully established, in part due to the lack of understanding of the complex microbial communities responsible for biological treatment. As water and wastewater treatment technologies have evolved over the past century, many biological treatments have remained largely 'black box' due to the lack of effective tools to identify the tens of thousands of species of microbes that inhabit a typical system and to track their dynamics with time. Instead, analysis has largely focused on basic water quality indicators. This dissertation takes important steps in advancing the implementation of the study of DNA and biodegradable organic carbon (BDOC) analysis to improve understanding of the mechanisms that drive different water reuse treatment technologies and to identify potential vulnerabilities. Insights gained through application of these tools are contextualized to observed operational conditions, process upsets, and water quality measurements. This helped to advance the use of DNA-based tools to better inform water treatment engineering practice. Specifically, this dissertation dives into the relationships between organic carbon and DNA-based markers within an advanced treatment train employing flocculation, coagulation, and sedimentation (FlocSed), ozonation, biologically active carbon (BAC) filtration, granular active carbon (GAC) contacting, and UV disinfection. Development and application of the BDOC test revealed that the bulk of organic carbon entering the treatment train is dissolved. Further, BDOC analysis served to characterize the impact of specific treatment processes and changes in operational conditions on both biodegradable and non-biodegradable organic carbon fractions. Such information can help to inform continued process optimization. Utilization of DNA-based technologies shed light on the functional capacity of microbial communities present within each stage of treatment and the fate of antibiotic resistance genes (ARGs). ARGs are of concern because, when present in human pathogens, they can result in the failure of antibiotics to cure deadly infections. Other functional genes of interest were also examined using the DNA-based analysis, including genes driving metabolic processes and nitrogen cycling that are critical to water purification during BAF treatment. Also, the DNA-based analyses made it possible to better understand the effects of disinfectants on microbes. Interestingly, some ARG types increased in relative abundance (a measure analogous to percent composition) response to treatments, such as disinfection, and others decreased. Characterization of the microbial communities and their dynamic response to changing operation conditions were also observed. For example, it was possible to characterize how the profiles of microbes changed with time, an ecological process called succession, during BAC filtration and GAC contacting. Generally, this analysis, coupled with the functional analysis, shed light on the important, divergent roles of bacterial communities on organic degradation during both BAC and GAC treatment. Finally, a study was conducted that compared the microbiome (i.e. entire microbial community) between a wide range of conventional drinking water, potable reuse water, and non-potable reuse waters. Here it was found that significant differences existed between the microbial communities of water intended for potable or non-potable usage. This work also looked to expand the application of NGS technologies beyond strictly academic research by developing the application of more advanced DNA-based tools for treatment train assessment and monitoring.
515

Virtual experiments as a contribution to the management of rivers impacted by microbial pollution and antibiotic resistance

Mishra, Sulagna 18 July 2024 (has links)
The contamination of rivers with potentially pathogenic bacteria poses health risks for users. This is particularly true when the bacteria are carriers of antibiotic resistance genes (ARG). Pathogenic bacteria and ARG are primarily discharged into rivers from wastewater treatment plants (WWTP). There, ARG are subject to the processes of transport, retention, and degradation. Simultaneously, they can also propagate through the growth of the carrier bacteria and by horizontal gene transfer. According to the current state of knowledge, the horizontal transfer of ARG is mediated predominantly by plasmid transfer. While the transport of bacteria in rivers has been intensively investigated, the relationship between the location of the wastewater discharges and their impact on microbial (and ARG) loading in the receiving waters downstream remains largely unexplored. Process-based mathematical models have been designed in the past to specifically describe the plasmid-mediated transfer of ARG. However, these models are used with numerous pragmatic simplifications whose effects on the computational outcomes have not been systematically examined. The present work uses virtual experiments (VE) to answer crucial questions regarding the spread of ARG in rivers. On the one hand, VE are used to compare alternative configurations of WWTP (in terms of size and location) within a catchment with respect to the resulting microbial contamination in the river network. On the other hand, VE are used to quantify the biases that arise in the estimation of plasmid transfer rates from laboratory experiments when the mathematical models used for this purpose have structural deficiencies. The rates of plasmid transfer determined from laboratory experiments provide an initial basis for assessing the potential importance of the horizontal transfer of ARG occurring in the water column along rivers. The knowledge gained makes an important contribution to describing the spread of ARG in rivers in the future through mathematical models and to identifying possible mitigation measures.
516

Application and Development of Ceragenins in Medical Device Coatings for Clinical Settings

Sherren, Elliot E. 21 June 2024 (has links) (PDF)
Hospital-acquired infections (HAIs) pose a significant and increasing threat to global health. One primary cause of this threat is increasing antibiotic resistance. As traditional antibiotics continue to grow less effective, there is an urgent need for novel antimicrobial strategies. This work explores the potential of ceragenins, also known as cationic steroid antimicrobials (CSAs), as a promising alternative to combat HAIs. Specifically, we investigated potential roles that CSAs can play in the context of multiple medical device coatings in healthcare settings. Ceragenins are synthetic mimic of antimicrobial peptides (AMPs) which exhibit broad-spectrum antimicrobial activity against many common pathogens that have been cited as high priority by global health organizations. Unlike traditional antibiotics, which rely on specificity to bacterial enzymes or processes, ceragenins disrupt microbial membranes generally. This mechanism of action allows ceragenins to bypass many of the related antibiotic resistance mutations of bacteria and fungi. As microbial membranes are a highly conserved and fundamental structure of these pathogens, it is much more difficult for microbes to develop mutations that prevent CSA binding. Additionally, ceragenins are resistant to both host and pathogenic proteolytic degradation and are cost-effective to produce, which place CSAs as an attractive alternative to traditional antibiotics. This research investigates the integration of ceragenins into various medical devices to prevent HAIs. Specifically, we investigated silicone tissue expanders, peripherally inserted central catheter (PICC) lines, and adhesive devices which include both polyacrylate and silicone scar tape. These studies include the development of coating techniques to maximize appropriate antimicrobial activity while maintaining stability and biocompatibility across these different base materials. Our experimental results demonstrate that ceragenin-coated devices significantly reduce microbial colonization and biofilm formation. We considered the length of antimicrobial activity needed and developed coatings that would be appropriate for those use cases. This reduction in harmful pathogenic colonization demonstrates their potential to improve patient outcomes and reduce healthcare costs associated with HAIs. Further research and development could facilitate the continued adoption of ceragenin-based coatings in medical devices, which can reduce the incidence of HAIs while contributing to the broader fight against antibiotic-resistant infections worldwide.
517

Evolution von Antibiotikaresistenzen in aquatischen Ökosystemen

Seiler, Claudia 07 May 2018 (has links)
The rising number of antibiotic resistant bacteria (ARB) may introduce to the post antibiotic era because they cause a loss of the therapeutic potential of antibiotics. For many years the important role of the natural environment as reservoir and dissemination pathway for ARB and responsible genes has been largely overlooked. However, especially aquatic ecosystems provide optimal conditions for the antibiotic resistance (AR) evolution: first, aquatic ecosystems are frequently affected by anthropogenic activities that cause multiple pollutions for example with heavy metals, that potentially cause co-selection of antibiotic- and heavy metal resistance. Second, aquatic ecosystems feature a dissemination pathway between human populations and natural environments via the urban water cycle. Water cycles between human associated environments (e.g. house holds and clinics) via waste water through waste water treatment plants into natural ecosystems (e.g. water bodies) and back as drinking water after purification. Third, ecosystem internal biotic interactions such as competition between bacteria and predation by the natural consumers seem to impact AR evolution sustainably. The present doctoral thesis focuses on the impact of abiotic and biotic factors on the proliferation of AR and responsible genes in natural aquatic environments, with special emphasis on (i) heavy metal driven co-selection of antibiotic and heavy metal resistance and (ii) on the impact of competition and predation on the evolution of AR. In order to quantify the risk of heavy metal driven co-selection for AR spread, I provide a first risk assessment based on literature values of environmental heavy metal loadings and related AR. Additionally, I developed a limit value named minimum co-selective concentration (MCC), which is the lowest concentration of a heavy metal that can potentially cause coselection in nature. It turned out that Cu, Zn, Ni, Hg, and Cd are suspected to be the main co-selecting heavy metals in the aquatic environment. I further investigated heavy metal driven co-selection of AR in a river ecosystem, the Western Bug River (Ukraine). I found indications for co-selection of resistance to five antibiotics (ciprofloxacin, gentamicin, amikacin, tobramycin, and cefepime) and two metals (Ni and Cd) caused by Ni- and Cd-levels. Both metals exceed their MCC for water samples and Cd additionally in sediments. As a second focal point the present work emphasis on ecological interactions effecting AR evolution. Currently three possible effects of ecological interactions on AR spread are discussed. First, environmental antibiotic levels are rather low, however they might favour ARB due to a competitive advantage. The reason is that even sublethal antibiotic levels reduce the growth of sensitive bacteria while resistant cells remain unaffected by the antibiotic action. Second, predation by protozoa is believed to impact conjugation between prey bacteria (and thus the transfer of DNA and potential resistance genes) by keeping bacteria in a growing stage that favours conjugation. Third, in order to escape predation by protozoa, bacteria evolved grazing defence mechanisms such as the formation of inedible biofilms, which can feedback on the evolution of AR. With an ordinary differential equation model, I tested the effect of low antibiotic levels and losses (e.g. due to predation) on the proliferation of ARB in a modelled planktonic system. In case that the model contains the mechanism that conjugation frequencies are highest during exponential growth, I found that (i) (grazing) losses enhance conjugation frequencies between bacteria and that (ii) medium levels of antibiotics and (grazing) losses favour resistant cells in the competition to sensitive bacteria. Biofilms are thought to be \'hot spots\' for conjugation but some plasmids have lower conjugation frequencies in biofilms compared to planktonic systems. As a first step, in order to discover predation effects on plasmid spread in plankton - biofilm systems I investigated grazing resistance of bacteria in grazing experiments. Both plankton and biofilm phenotypes were consumed, when exposed to their specialized grazer (either plankton-feeder or biofilmfeeder), whereas the other phenotype remained grazing-resistant and thus became the dominant prey type. Both predators together effectively control planktonic and biofilm prey. With regards to the spread of AR-genes via conjugation, I speculate that the feeding preference of the present predator can affect the invasion success of resistance plasmids in planktonic - biofilm systems. For dynamic systems, I assume that dynamics of predator and prey traits (plankton vs. biofilm-feeder and biofilm vs. planktonic prey) will lead to dynamics of conjugation frequencies in planktonic or biofilm bacteria. I assume that conjugation events are more frequent in the dominant prey type (plankton or biofilm). However, other factors such as pili-type of the plasmid (short and rigid pili, prefers conjugation in biofilms or long and flexible pili, prefers conjugation in plankton) might additionally influence plasmid invasion success in plankton - biofilm morphotypes.
518

Two - Stage AnMBR for Removal of UV Quenching Organic Carbon from Landfill Leachates: Feasibility and Microbial Community Analyses

Pathak, Ankit Bidhan 13 February 2017 (has links)
Landfilling is the most widely used method for the disposal of municipal solid wastes (MSW) in the United States due to its simplicity and low cost. According to the 2014 report on Advancing Sustainable Materials Management by the USEPA, only 34% of the total MSW generated in the US was recycled, while 13% was combusted for energy recovery. In 2014, 53% of the MSW generated, (i.e. 136 million tons) in the US was landfilled. The treatment of landfill leachates, generated by percolation of water through the landfill, primarily due to precipitation, has been found to be one of the major challenges associated with landfill operation and management. Currently, leachates from most landfills are discharged into wastewater treatment plants, where they get treated along with domestic sewage. Issues associated with treatment of landfill leachates due to their high nitrogen and heavy metal content have been widely studied. Recently, it has been observed that the organic carbon in landfill leachates, specifically humic and fulvic acids (together referred to as "humic substances") contain aromatic groups that can absorb large amounts of ultraviolet (UV) light, greatly reducing the UV transmissivity in wastewater plants using UV disinfection as the final treatment step. This interference with UV disinfection is observed even when landfill leachates constitute a very small fraction (of the order of 1%) of the total volumetric flow into wastewater treatment plants. Humic substances are present as dissolved organic matter (DOM) and typically show very low biodegradability. Removing these substances using chemical treatment or membrane processes is an expensive proposition. However, the concentrations of humic substances are found to be reduced in leachates from landfill cells that have aged for several years, suggesting that these substances may be degraded under the conditions of long-term landfilling. The primary objective of this research was to use a two-stage process employing thermophilic pretreatment followed by a mesophilic anaerobic membrane bioreactor (AnMBR) to mimic the conditions of long-term landfilling. The AnMBR was designed to keep biomass inside the reactor and accelerate degradation of biologically recalcitrant organic carbon such as humic substances. The treatment goal was to reduce UV absorbance in raw landfill leachates, potentially providing landfills with an innovative on-site biological treatment option prior to discharging leachates into wastewater treatment plants. The system was operated over 14 months, during which time over 50% of UV-quenching organic carbon and 45% of UV absorbance was consistently removed. To the best of our knowledge, these removal values are higher than any reported using biological treatment in the literature. Comparative studies were also performed to evaluate the performance of this system in treating young leachates versus aged leachates. Next-generation DNA sequencing and quantitative PCR (qPCR) were used to characterize the microbial community in raw landfill leachates and the bioreactors treating landfill leachate. Analysis of microbial community structure and function revealed the presence of known degraders of humic substances in raw as well as treated landfill leachates. The total number of organisms in the bioreactors were found to be higher than in raw leachate. Gene markers corresponding to pathogenic bacteria and a variety of antibiotic resistance genes (ARGs) were detected in raw landfill leachates and the also in the reactors treating leachate, which makes it necessary to compare these ARG levels with wastewater treatment in order to determine if leachates can act as sources of ARG addition into wastewater treatment plants. In addition, the high UV absorbance of leachates could hinder the removal of ARBs and ARGs by UV disinfection, allowing their release into surface water bodies and aiding their proliferation in natural and engineered systems. / Ph. D. / Municipal solid waste is most often disposed by dumping it in landfills. Percolation of water through these landfills due to precipitation or the intrusion of surface or groundwater, results in the formation of landfill leachate, a mixture of organic and inorganic contaminants, at the bottom of the landfill. Landfills are therefore lined with special materials to prevent leachate from seeping into soil or groundwater and have sophisticated collection systems to periodically extract and dispose leachate. Perhaps the most commonly used method for the disposal of landfill leachates is discharge into wastewater treatment plants, where leachates can cause toxicity to biological processes due to their high organic load as well as their substantial heavy metal content. In the last decade or so, it has been established that leachates can absorb UV light considerably by virtue of aromatic organic compounds present in them, causing inhibition of UV disinfection in wastewater treatment. Thus, leachates must be appropriately treated to reduce their capacity to absorb UV light prior to discharge into wastewater treatment plants. This study employed a novel two – stage reactor system to treat landfill leachates in order to reduce their UV-quenching ability. The system was successfully operated over 14 months and was able to remove more than half of the UV light absorbing organic carbon from landfill leachate. Additionally, samples of biomass isolated from untreated landfill leachates and the reactors treating them revealed the potential presence of pathogenic bacteria and antibiotic resistance genes. Preliminary data suggests that landfill leachates might have large antibiotic resistance content, higher than that observed in wastewater and other engineered systems.
519

Développement des nouveaux outils de surveillance de l'émergence des bactéries à Gram négatif multirésistantes

Berrazeg, Meryem 03 June 2013 (has links)
L'augmentation et la dissémination de la résistance aux antibiotiques chez les bacilles à Gram-négatif, particulièrement les Entérobactéries, les bactéries du genre Pseudomonas et Acinetobacter, représentent un problème majeur de santé publique. Les infections nosocomiales causées par les bactéries multi-résistantes ont conduit non seulement à une augmentation de la mortalité, de la morbidité et du coût de traitement, mais aussi continuent à mettre en danger la vie des patients surtout immunodéprimés. L'utilisation abusive et non contrôlée des antibiotiques a grandement contribué à la large diffusion de la résistance aux antibiotiques. Cependant, des études récentes ont démontré que cette résistance pouvait émerger à partir de sources anciennes et/ou environnementales. Ainsi, face à cette préoccupation mondiale et suite à de nombreuses recommandations, plusieurs études épidémiologiques et moléculaires ont été rapportées afin de contrôler et surveiller la diffusion et la dissémination de la résistance aux antibiotiques. Il est cependant prioritaire de développer des nouveaux outils de surveillance de la résistance aux antibiotiques. C'est dans cette optique que ce projet de thèse s'articule avec comme objectifs :- Le développement et la mise en place de nouveaux outils et logiciels de surveillance et de diagnostic des bactéries multi-résistantes, - La réalisation des études d'épidémiologie moléculaire sur les isolats cliniques de bactéries multi-résistantes responsables d'épidémies. / The increase and spread of multidrug-resistant (MDR) gram-negative bacteria especially Enterobacteriaceae, Pseudomonas, and Acinetobacter (E.P.A) species have become a major concern worldwide. The hospital-acquired infections caused by MDR bacteria have led not only to an increase in mortality, morbidity, and cost of treatment, but also continue to endanger the life of patients, especially those immunocompromised. Although, the frequent misuse of antibiotic drug has greatly contributed to worldwide dissemination of antibiotics resistance. Recent studies have shown that these resistance determinants could emerge from ancient or environmental sources. Front of this worldwide concern, and various recommendations, several epidemiological and molecular studies have been reported in order to control the spread and the dissemination of the antibiotic resistance. However, it is a priority to develop new tools for monitoring antibiotic resistance. Therefore, it is in this context that the project of this thesis was conducted with two essential objectives: -The development and implementation of news tools and software for monitoring and diagnosis of potential MDR bacteria. -The achievement of molecular epidemiology studies from clinical MDR bacteria responsible of outbreak.
520

Incidence and mechanism of antibiotic resistance of Streptococcus Agalactiae isolates from pregnant women and their babies at Dr George Mukhari Academic Hospital, Pretoria

Bolukaoto, Yenga John 10 1900 (has links)
BACKGROUND AND OBJECTIVES: Streptococcus agalactiae (Group B Streptococcus, GBS) is the leading cause of neonatal infections and deaths in human. It can also cause infections in pregnant women and non-pregnant adults. Penicillin and ampicillin are antibiotics of choice for the treatment of GBS infections. Erythromycin and clindamycin are used as alternative therapy in penicillin allergic patients, however resistance to these agents has been increasingly observed. This present study was undertaken to determine the colonization rate of GBS, susceptibility profile and the mechanism of antibiotic resistance in pregnant women and their babies at Dr. George Mukhari Academic Hospital in Pretoria. METHODS: Rectal and vaginal swabs were collected from pregnant women; ear and umbilical swabs from newborns over an 11 month period. Samples were cultured on selective media (CNA agar and Todd-Hewitt broth) and GBS positively identified using morphological and biochemical tests including Gram staining, hemolytic activity, catalase test, bile esculin, CAMP test and Latex agglutination test. The susceptibility testing was done using the Kirby-Bauer and E-test methods. The D-test method was used to determine the inducible clindamycin resistance. Multiplex PCR with were used to detect different genes coding for resistance. RESULTS: Out of the 413 patients evaluated, 128 (30.9%) were positive with GBS. All isolates were sensitive to penicillin and ampicillin. Erythromycin and clindamycin resistance was 21.1% and 17.2% respectively; of which 69% harbouring constitutive MLBB, 17.4% inducible MLSB. The alteration of ribosomal target encoded by ermB genes was the commonest mechanism of resistance observed in 55% of isolates, 38% of isolates had both ermB and linB genes and efflux pump mediated by mefA genes was detected in one of isolates. Conclusion: This study reaffirms the appropriateness of penicillin as the antibiotic of choice for treating GBS infection. However it raises the challenges of resistance to the macrolides and lincosamides. More GBS treatment options for penicillin allergic patients need to be researched. / Health Studies / M.Sc. (Life Sciences (Microbiology))

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