Thèses : « Antibiotic resistance bacteria (ARB) »

1

Wind, Lauren Lee. « Persistence of Culturable Antibiotic Resistant Fecal Coliforms From Manure Amended Vegetable Fields ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/86262.

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The reduced efficacy of antibiotics in treating common infections is one of the most pressing health concerns of the 21st Century. Increasing evidence links the widespread use of antibiotics in livestock production to the transfer of bacteria carrying antibiotic resistance genes to the broader environment. It is therefore critical to understand the persistence and dissemination of resistance in agricultural soils to understand potential threats to consumers. The goal of this large-scale agricultural field experiment was to identify the effects of crop (lettuce, radish) and fertilizer type (inorganic, compost, raw manure) on the incidence and persistence of antibiotic-resistant fecal coliforms, a common family of fecal indicator bacteria used to track the environmental spread of antibiotic resistance. Soil samples were collected eight times over a 120-day period and analyzed for fecal coliforms utlizing a suite of MacConkey agars supplemented with different antibiotics (ceftazidime, clindamycin, erythromycin, sulfamethoxazole, and tetracycline). Given the number of samples with resistant fecal coliform concentrations below the limit of detection, analyses to identify the effects of soil treatment and crop relied on Zero-inflated Poisson Regressions. Antibiotic-resistant culturable fecal coliforms were recoverable from soils across all treatments immediately following application, though persistence throughout the experiment varied by antibiotic. Sulfamethoxazole- and tetracycline-resistant fecal coliforms were nondetectable after Day 1; this was expected, as the cattle supplying the manure amendments were not treated with these antibiotics or similar analogs. Clindamycin- and erythromycin-resistant fecal coliforms were nondetectable after 42 days but rebounded on Day 90 in the soil; both of these drugs were of the same antibiotic class as the ones used to treat the dairy cattle during the manure collection period. Ceftazidime-resistant fecal coliform levels were consistently high throughout the duration of the growing season. No statistical differences were observed between root and aboveground crops. Results suggest that soils amended with raw or composted dairy manure are at risk of contamination with antibiotic resistant fecal coliforms; however, composting decreased the antibiotic resistant fecal coliform levels of the macrolide (erythromycin) and lincosamide (clindamycin) antibiotic classes administered to the dairy cattle (cephapirin and pirlimycin).
Master of Science

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Riquelme, Breazeal Maria Virginia. « Improved monitoring of emerging environmental biocontaminants through (nano)biosensors and molecular analyses ». Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/83419.

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Outputs of human-derived chemicals and constituents to the environment, and shifts in these outputs, can result in unintended consequences to human and ecological health. One such shift is the advent of the modern antibiotic era, in which mass production and outputs of antibiotics, which are mostly naturally-derived microbial defense compounds and include a few synthetic antimicrobials, has profound implications for contributing to the spread of antibiotic resistance. Antibiotic resistance arises from mutations and/or sharing of antibiotic resistance genes (ARGs) among bacteria via horizontal gene transfer, with carriage of ARGs by pathogenic bacteria of particular concern to human health. While most attention to stopping the spread of antibiotic resistance has been devoted to the clinic, it is critical to consider the environmental origin, ecology and pathways by which antibiotic resistance spreads in order to develop comprehensive strategies to combat antibiotic resistance. In particular, wastewater treatment plants (WWTPs) represent a potentially key critical control point given that they receive antibiotic resistant bacteria (ARB) and ARGs from the population, which are then routed to activated sludge biological treatment, consisting of high density, highly active microbial populations. The research projects described in this dissertation aimed to explore the occurrence of ARGs in WWTPs, particularly WWTPs in developing countries representing the extremes of what is expected to be encountered in terms of potential to spread antibiotic resistance, and to improve and apply novel technologies for monitoring key markers of antibiotic resistance in WWTPs and affected environments. The pathogen Staphylococcus aureus and a corresponding ARG (methicillin resistance mecA gene) were chosen as model biocontaminants of concern due to their environmental and public health relevance. The results reported in Chapters 3-5 advance the knowledge of bio(nano)sensing techniques and highlight areas of promise and challenge. The results reported in Chapter 2 provided insight into the baseline levels of ARGs expected in a highly impacted WWTP in India, thereby highlighting the magnitude and global scale of the problem of antibiotic resistance as well as the need for innovative solutions.
Ph. D.

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Williams, Robert Kyle. « Effect of Composting on the Prevalence of Antibiotic Resistant Bacteria and Resistance Genes in Cattle Manure ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74952.

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Antibiotic resistance is a growing human health threat, making infections more difficult to treat and increasing fatalities from and cost of treatment of associated diseases. The rise of multidrug resistant pathogens threatens a return to the pre-antibiotic era where even the most common infections may be impossible to treat. It is estimated that the majority of global antibiotic use, and use in the U.S., is dedicated towards livestock, where they are used to promote growth, treat, or prevent disease. Given that exposure to antibiotics selects for antibiotic resistant bacteria (ARBs) and can stimulate the horizontal transfer of their associated antibiotic resistance genes (ARGs), it is important to examine livestock operations as a reservoir of resistance. Correspondingly, there is growing interest in identifying how agricultural practices can limit the potential for spread of antibiotic resistance through the "farm to fork continuum," starting with antibiotic use practices, manure management and land application and ending with the spread of ARBs and ARGs present onto edible crops and serving as a route of exposure to consumers. This study focused specifically on the effect of composting on the prevalence of ARBs and ARGs in cattle manure. Three composting trials were performed: small-scale, heat-controlled, and large-scale. The small-scale composting trial compared dairy and beef manures, with or without antibiotic treatment (treated beef cattle received chlortetracycline, sulfamethazine, and tylosin while treated dairy cattle received cephapirin and pirlimycin), subject to either static or turned composting. The heat-controlled composting trial examined only dairy manure, with or without antibiotic treatment, subject to static composting, but using external heat tape applied to the composting tumblers to extend the duration of the thermophilic (>55°C) temperature range. The large-scale composting trial examined dairy manure, with or without antibiotic treatment, subject to static composting at a much larger scale that is more realistic to typical farm practices. Samples were analyzed to assess phenotypic resistance using the Kirby Bauer disk diffusion method and by diluting and plating onto antibiotic-supplemented agar. Genetic markers of resistance were also assessed using quantitative polymerase chain reaction (qPCR) to quantify sul1 and tet(W) ARGs; metagenomic DNA sequencing and analysis were also performed to assess and compare total ARG abundance and types across all samples. Results indicate that composting can enrich indicators of phenotypic and genetic resistance traits to certain antibiotics, but that most ARGs are successfully attenuated during composting, as evidenced by the metagenomic sequencing. Maintaining thermophilic composting temperatures for adequate time is necessary for the effective elimination of enteric bacteria. This study suggests that indicator bacteria that survive composting tend to be more resistant than those in the original raw manure; however, extending the thermophilic stage of composting, as was done in the heat-controlled trial, can reduce target indicator bacteria below detection limits. Of the two ARGs specifically quantified via qPCR, prior administration of antibiotics to cattle only had a significant impact on tet(W). There was not an obvious difference in the final antibiotic resistance profiles in the finished beef versus dairy manure composts according to metagenomics analysis. Based on these results, composting is promising as a method of attenuating ARGs, but further research is necessary to examine in depth all of the complex interactions that occur during the composting process to maximize performance. If not applied appropriately, e.g., if time and temperature guidelines are not enforced, then there is potential that composting could exacerbate the spread of certain types of antibiotic resistance.
Master of Science

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RIVA, FRANCESCO. « ANTIBIOTIC RESISTANCE SPREAD MEDIATED BY HORIZONTAL GENE TRANSFER IN THE AGRI-FOOD ECOSYSTEM ». Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/914666.

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Antibiotic resistance (AR) is a public problem for human health and food safety. Globalization has contributed to create an intense connection among human and animal health and the environment, allowing bacteria and their genes to move among all these compartments, making a “one-health approach” necessary to counteract this phenomenon. Horizontal gene transfer (HGT), which contributes to AR determinants diffusion, is mediated by three main mechanisms: i) conjugation, ii) transduction, and ii) natural transformation. Several environments linked to the agri-food system are both sources of AR determinants and hot spots of HGT. One of the main routes of AR spread in the agri-food system could be represented by the use of treated wastewater as irrigation source: the reuse of water is indeed a common practice in several countries, including Europe, to fight the water crisis exacerbated by global warming. Wastewater treatment plants (WWTPs) could be one of the main sources of free antibiotic resistance genes (ARGs) which could be released in freshwater bodies. AR determinants present in the treated wastewater would thus enter in the food production through irrigation and could be acquired by pathogenic strains, potentially posing a risk to human health. Even if the presence and the related issues about AR determinants in the environment are well known, there are many aspects which have to be understood e.g. the relative contributions of different sources of AR determinants in the environment, also considering HGT events. Since information about the relationship between environmental HGT and spread of AR determinants is limited, the aim of this PhD thesis was to evaluate the diffusion of ARGs through natural transformation and conjugation in environment or in environmental-like conditions to describe several possible routes of AR spread in the agri-food system. Zooplankton plays a crucial role in waterbodies, being closely linked to bacteria inhabiting aquatic environments in several ecological function, and it establishes a connection with bacterial communities that are inhabitant of the environment in which it lives. Due to the interaction between bacteria and zooplankton, together with the presence of Escherichia coli in waterbodies, derived from human and animal faecal waste, I first evaluated the relationship established between zooplankton, with the model Daphnia obtusa, and E. coli, isolated from it, suggesting that Daphnia could help the bacterium to adapt to the harsh condition that could be found in the freshwater bodies, highlighting the possible role of zooplankton in the diffusion of antibiotic resistant bacteria (ARB) in the agri-food system. The interaction observed between Daphnia and E. coli in the first part of this thesis, together with the knowledge of the presence of ARGs in aquatic environment and the moderate ability to E. coli to acquire DNA through natural transformation, have thus led to the study of natural transformation in zooplankton-associated bacteria, also in terms to unveil the animal influence. Indeed, I studied the natural transformation of the environmental E. coli strain ED1, isolated from D. obtusa, mimicking environmental conditions which could be found in the agri-food system. ED1 ability to acquire exogenous DNA, with a higher frequency than the one of a laboratory strain, together with its ability to thrive in lettuce rhizosphere, underlined the importance to investigate the spread of AR determinants in the agri-food system, especially in the rhizosphere of plants which are usually raw-consumed. Moreover, the possible influence of the zooplankton on natural transformation was investigated through the use of D. obtusa and Acinetobacter baylyi BD413, known to be naturally competent to acquire DNA. A decrease of transformation frequency was observed in presence of Daphnia, due to the degradation of exogenous DNA, highlighting the need of further investigations on zooplankton involvement in ARGs diffusion in aquatic environments. Considering possible routes of diffusion of AR determinants in the agri-food system, i.e. from WWTPs to freshwater bodies and their inhabitant community, to crops and plants, I then devoted my attention on HGT by conjugation in rhizosphere of lettuce, used as model of raw-eaten vegetables. The aim of this work was the construction of a donor strain belonging to the Enterobacteriaceae family and isolated from treated wastewater. Specifically, Klebsiella variicola subsp. variicola was genetically manipulated through the chromosomal tagging with a mCherry gene and a constitutively expressed LacIq gene, and the insertion of the broad host range plasmid pKJK5::gfp::KanR, carrying a green fluorescent protein gene (Gfp) under the control of laclq repressible promoter, and thus resulting in the absence of gfp expression in the donor. The gfp was expressed only in recipient strains, following the mobilization of the plasmid through conjugation. The strain ability to donate the plasmid within the bacterial community of lettuce rhizosphere and its ability to colonize the plant root system were verified, making K. variicola subsp. variicola EEF15::lacIq-pLppmCherry-GmR with plasmid pKJK5::gfp a perfect candidate for the study of conjugation in plants microniches. Finally, I contributed to prepare a critical review on microbial assisted phytodepuration and the use of plant growth promoting bacteria in Constructed Wetland (CW) systems, with a focus on HGT events and the possible spread of AR determinants in the rhizosphere of plants used in phytodepuration. Data collected in this PhD project underline the importance to study the diffusion of AR determinants trough HGT events in the agri-food system, in order to create a rank risk and a risk assessment map to mitigate the diffusion of AR.

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Hiliare, Sheldon. « Impact of Manure Land Management Practices on Manure Borne Antibiotic Resistant Elements (AREs) in Agroecosystems ». Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102218.

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Rising global antibiotic resistance has caused concerns over sources and pathways for the spread of contributing factors. Majority of the antimicrobials used in the U.S. are involved in veterinary medicine, primarily with livestock rearing. Animal manure land application integrates livestock farming and agroecosystems. This manure contains antibiotic resistant elements (AREs) (resistant bacteria, resistance genes, and veterinary antibiotics) that contribute towards antimicrobial resistance. Altering manure application techniques can reduce surface runoff of other contaminants such as excess N and P, pesticides, and hormones, that can impact water quality. Conventional tillage practices in the U.S. has reduced or stopped, making subsurface injection of manure a promising option when compared to surface application. Our research compared manure application methods, manure application seasons, cropping system, and manure-rainfall time gaps to gauge the impact on AREs in the environment. Two field-scale rainfall simulation studies were conducted along with one laboratory study. Using the injection method lowered concentrations of manure associated AREs entering surface runoff. When manure was surface applied and rainfall occurred 7 d after application, 9-30 times less resistant fecal coliform bacteria (FCB) entered surface runoff when compared to 1 d time gap for that broadcast method. Within a day of manure application, antibiotic resistance gene (ARG) profiles in soil began to differ from each other based on manure application and soil ARG richness in all manure-amended soil increased compared to the background. Runoff from injection plots contained 52 ARGs with higher abundance compared to runoff from surface applied plots. ARGs in the former were more correlated to soil and more correlated to manure in the latter. The highest antibiotic concentrations were in the injection slit soil of those plots. Antibiotic concentrations in samples corresponded positively to concentrations of resistant FCB and ARGs, and there was a positive correlation between resistant FCB and their associated ARGs (Spearman's ρ = 0.43-0.63). A CRIISPR-Cas12a assay for quantification of ARGs in environmental samples was just as precise as conventional methods. There is also potential for in-situ detection. These combined results can hopefully help farmers improve manure management practices that mitigate spread of AREs to surrounding water, crops, and soil.
Doctor of Philosophy
Rising global antibiotic resistance cause concerns over sources and pathways for the spread of contributing factors. Most of the antimicrobials used in the U.S. are involved in veterinary medicine, especially with livestock rearing. Overuse of antibiotics that are medically important to human medicine compromises the effectiveness of our medicines. Animal manure contains antibiotic resistant elements (AREs) such as resistant bacteria, resistance genes, and antibiotics) that contribute towards resistance issues. Once these AREs enter the environment, they can be taken up by crops, runoff into surface water or leached into ground water, or even reside within the animal products we consume. Altering manure application techniques is beneficial for nutrient conservation but also potentially for reducing ARE spread. With our research, we compared manure application methods, manure application seasons, cropping systems, and manure-rainfall time gaps to find ways to balance the need for manure application and the spread of resistance. We used two field-scale rainfall simulation studies along with one laboratory study. Overall, using the injection method resulted in significantly lower concentrations of manure associated AREs entering surface runoff. When manure was surface applied and rainfall occurred 7 d after application, less resistant fecal coliform bacteria (FCB) entered surface runoff when compared to the 1 d time gap for broadcast methods. Within a day of manure application, antibiotic resistance gene (ARG) profiles in soil began to differ from each other and soil ARG totals in all manure applied soil increased compared to the background. Runoff from injection plots contained more soil ARGs and runoff from surface applied plots containing more manure associated ARGs. The subsurface injection method also caused highest antibiotic concentrations in the injection slit soil of those plots. High antibiotic concentrations in samples generally meant high concentrations of resistant FCB and ARGs, and resistant FCB were also found with their associated ARGs as well. A CRISPR-Cas12a assay for quantification of ARGs in environmental samples was just as precise as conventional methods. There is also potential for onsite detection. These combined results can hopefully help farmers improve manure management practices that mitigate spread of AREs to surrounding water, crops, and soil.

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Zhang, Lu. « Establishment and Development of Antibiotic Resistant Bacteria in Host Gastrointestinal Tract—Food, Drug, or Are We Born with It ? » The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316186957.

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Nagulapally, Sujatha Reddy. « Antibiotic resistance patterns in municipal wastewater bacteria ». Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/331.

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Roe, Darcie Elizabeth. « Prevalence and mechanisms of antibiotic resistance in oral bacteria ». Thesis, Connect to this title online ; UW restricted, 1996. http://hdl.handle.net/1773/9310.

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Melnyk, Anita. « The Evolution of Antibiotic Resistance in Experimental Populations of Bacteria ». Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34556.

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Antibiotic resistance is a major threat to public health. Understanding how it evolves, and the genes that underlie resistance, is the main goal of my Ph.D. research. After a resistance mutation arises, it’s fate within a pathogen population will be etermined in part by its fitness: mutations that suffer little or no fitness cost are more likely to persist in the absence of antibiotic treatment. My research centers on understanding this process better by gaining knowledge about the spectrum of fitness effects associated with antibiotic resistance mutations. Using a meta-analysis framework I find that, across a range of antibiotics and pathogens, on average single resistance mutations exhibit fitness costs in the absence of drug, however, there are instances of cost-free mutations. To evaluate the conditions leading to the persistence of resistance in the absence of antibiotic, I use experimental evolution of the opportunistic pathogen Pseudomonas aeruginosa and the antibiotic ciprofloxacin to investigate the phenotypic and genetic differences associated with constant and fluctuating drug treatment. I find that fluctuating drug treatment leads to the evolution of cost-free resistance. At the genetic level, cost-free resistance is the result of second-site mutations that compensate for the fitness cost associated with ciprofloxacin-resistance mutations. Further examination of the resistance mutations shows a lack of epistatic interactions between co-occurring mutations that confer resistance within a single isolate. To investigate the repeatability of the genetic causes of resistance, I execute a second evolution experiment using multiple clinical strains of P. aeruginosa adapting to a constant ciprofloxacin selective pressure. I find a remarkable lack of parallel evolution at the genomic level both within and between different P. aeruginosa strains. I have shown that antibiotic resistance is costly, and that these costs can be ameliorated by second-site mutations that readily arise over short time scales. Additionally, different strains of the same bacteria can gain resistance through a diverse set of genetic mutations. On an applied level these results are not positive; combating resistance evolution will be difficult because pathogens can easily compensate fitness costs of resistance, and resistance itself can be gained via a large number of genetic targets.

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Suarez, Rachel. « Chemical disinfectant resistance in multiple antibiotic resistant and susceptible bacteria ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57585.pdf.

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Lillro, Ejla. « Image Sensor System for Detection of Bacteria and Antibiotic Resistance ». Thesis, KTH, Skolan för teknik och hälsa (STH), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179399.

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Antibiotic resistance is now a recognized problem in global health. In attempts to find solutions to detect bacteria causing antibiotic resistance we turn to technological solutions that are miniaturized, portable and cheap. The current diagnostic procedures cannot provide correct information outside laboratory settings, at the point-of-care, within necessary time. This has led to ineffective treatment of urinary tract infections causing recurrent infections and multi-drug resistant bacteria to spread. The bacteria genes show which antibiotic that is required to eliminate disease and spread of resistance. Hence, the solution would be to perform nucleic acid testing at the point-of-care. By using new DNA amplification methods it is possible to miniaturize the diagnostic test to a so-called Lab-on-a-chip. These solutions would enable sample-in-results-out capability of the system at the point-of-care. For this to work one of the most important factors is fluorescent signal read-out from DNA amplification products. In this project the design parameters of such a read-out device was investigated with focus on image sensor sensitivity and device integration. During the project it was found that a low-cost commercial image sensor could be used to record images of a (3.76 x 2.74 mm2) micro well array of nanoliter sized PCR chambers. Different imaging artifacts appearing during sample partitioning were observed, distance dependency between sensor surface well array was investigate, and finally the image sensor function was compared to a fluorescent microscope.

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Gallagher, L. K., Brian G. Evanshen, Kurt J. Maier et Phillip R. Scheuerman. « Bacterial Source Tracking in the Sinking Creek Watershed, using Antibiotic Resistance Analysis (ARA) and Ribotyping ». Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etsu-works/2946.

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Leonard, Anne Frances Clare. « Are bacteria in the coastal zone a threat to human health ? » Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/22805.

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Faecal pollution regularly contaminates surface waters, introducing microorganisms, including bacteria and bacteria resistant to antibiotics, to coastal waters. People can come into contact with these potentially harmful microbes when they enjoy recreational activities in the sea. Understanding the risk to bathers of acquiring infections from the sea is important for developing effective intervention strategies to protect human health. This thesis consists of four original studies which aim to answer the question ‘are bacteria in the coastal zone a threat to human health’? First, we describe a systematic review on the risk of acquiring infections from recreational use of coastal waters. Synthesising risk estimates of reporting various symptoms of ill health, we quantify this risk as well as appraise the evidence that these infections are acquired from bathing in coastal waters. The results of the second study - a large online survey - corroborate these findings and provide updated estimates of risk for UK bathers. Third, we assess the risk of ingesting antibiotic resistant bacteria among UK coastal water users. In the final study, we measured the prevalence of faecal carriage of antibiotic resistant bacteria among a highly exposed group – surfers, and in an unexposed group (non-surfers). We conclude that despite improvements made to the collection, treatment and discharge of sewage, and initiatives to communicate water quality to members of the public in recent years, people who bathe in coastal waters are still at an increased risk of adverse health outcomes, whether this is experiencing symptoms of ill health, or exposure to and colonisation by antibiotic resistant bacteria.

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Hernández, Jorge. « Human Pathogens and Antibiotic Resistant Bacteria in Polar Regions ». Doctoral thesis, Uppsala universitet, Institutionen för medicinska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230700.

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Coincident with human activity in recent decades, human-associated microorganisms have arrived to the Antarctic region, possibly linked to increasing presence of scientific bases and ship-borne tourists. In the Arctic, humans have been present for a very long time, and the few parts of the Arctic without human activities is decreasing with time. The studies in this thesis investigate the occurrence of different pathogens in Antarctic and Arctic wildlife, especially in birds. The first study shows the existence of Enteropatogenic Escherichia coli (EPEC) in Antarctic fur seals. The EPEC isolates were so called atypical EPECs, carrying the eae gene but lacking the bfp gene. This is the first record of a diarrheogenic E. coli in wild animals in the Antarctic. The second study displays that spreading of antibiotic resistance mechanisms appears to be much more efficient than previously was known. Enterococcus faecium isolated from Alaskan birds showed high resistance to vancomycin and teicoplanin, but also to ampicillin and ciprofloxacin. These isolates also carried vanA genes and the virulent esp gene, which places the isolates in the clinical clone CC17 and indicates the isolates had a human origin. Bacteria from birds that reside in the Bering Strait region in the third study, demonstrates that only six of 145 E. coli from 532 birds had reduced antibiotic susceptibility. Despite this, selective screen on E. coli showed only four ESBL-producing isolates. The four E. coli isolates carried CTX-M genes. One isolate belonged to the E. coli O25b - ST131 genotype, which is a successful clone with a global spread. In the fourth study, 123 seawater samples and 400 fresh penguin feces were analyzed. From these, 71 E. coli strains were isolated and only one E. coli from penguins was resistant to one antibiotic (cloramfenicol), whereas in E. coli from seawater, resistance against ampicillin, tetracycline, streptomycin and trim-sulfa were detected. E. coli carrying ESBL type CTX -M genes were also detected and Multilocus Sequencing Typing (MLST) showed six different sequence types (ST) previously reported in humans: ST131, ST227, ST401, ST410, ST685 and ST937. In the short time interval between the second study (2005) and the third study (2010) in relation to the fifth study (2012) we found a dramatic increase in antibiotic-resistant genes in the Arctic region. Enterococci, E. coli, and Kl. pneumoniae carried antibiotic resistance genes to an extent and variety not previously reported. E. coli from Arctic birds showed resistant to 1, 2, 3, 4, and 5 different antibiotics. Resistant gene type vanA was confirmed in enterococci and ESBL genes type TEM, SHV and CTX-M in E. coli and Kl. pneumoniae was detected. Multilocus Sequencing typing (MLST), indicating that both E. coli and Kl. pneumoniae carrying ESBL markers that connects them to the humans. In summary, the combined studies strengthen that bacteria that cause infections in humans could spread to relatively pristine environments. We concluded that human and associated antibiotic-resistant bacteria has reached a global level, then we showed that ESBL- carrying bacteria circulating nowadays also in the last ESBL-free continent, Antarctica.

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Jacobs, Kyle Bowers. « Recovery of Antibiotic Resistance Genes From Agricultural Runoff ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/88743.

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The reduced capacity of antibiotics to treat infections is one of the greatest health concerns that society faces. There is substantial evidence that links this reduced capacity with the widespread use of antibiotics in livestock production. Livestock can act as reservoirs of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria, which can pass resistance on in the livestock's manure. It is important to understand the fate of antibiotic resistance genes and resistant bacteria in the environment after land-application of manure-based amendments. The goal of this field-scale study was to identify the effects of soil amendments (inorganic fertilizer, compost, or raw manure) and crop cover (lettuce or radish) on sediment transfer, fecal indicator bacteria (FIB), and release of ARGs in runoff over six storm events. Two FIB (Escherichia coli and enterococci) and two ARGs (sulI and ermB) were quantified in runoff from each of the constructed plots throughout the growing season. FIB and ARGs were recovered from all plots, including control plots indicating a background level within the soil. Additionally, only the effects of variability among individual storms had an impact on the concentration of FIB in runoff. Vegetative cover and storm variability affected sediment release. A trend of higher sul1 and ermB in runoff from compost and raw manure-amended plots for at least 2 months after planting crops was observed. Only one of these ARGs (ermB) is associated with the class of drugs given to the dairy cows used for the manure and compost, indicating inherent carriage of some ARGs independent of the type of antibiotic administered, and such genes can persist in the environment. These results suggest that there is a risk of ARGs being carried into areas downgradient from agricultural plots that have been amended with compost or manure.
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Davis, Ian Jonathan. « Characterisation of heavy metal & ; antibiotic resistance genes in oral bacteria ». Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408917.

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Ahmen, Mohamed Omar Basher. « Zoonotic bacteria and antibiotic resistance in the GI tract of horses ». Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425475.

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Mak, Jennifer Ka Yan Biotechnology &amp Biomolecular Sciences Faculty of Science UNSW. « Integrons, resistance genes and their dissemination (in Gram- Negative Bacteria) ». Awarded By:University of New South Wales. Biotechnology & ; Biomolecular Sciences, 2009. http://handle.unsw.edu.au/1959.4/44381.

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Antibiotic resistance is increasing worldwide, which is threatening the effectiveness of even the most potent and recent antibiotics. The successful treatment of disease is hampered due to the multidrug resistant (MDR) phenotype exhibited by the bacterial pathogens. Therefore, the aims of this thesis were to investigate MDR through several different approaches. Integrons are important contributors to the MDR profile of nosocomial isolates within Australia, therefore the incidence of integrons was assessed in a collection of 72 conjugative clinical plasmids isolated from E. coli, a cohort of 30 urinary tract infection (UTI) isolates and a cohort of four bacteria producing metallo-beta-lactamases (MBLs). Integrons were found in 63% (45/72) of the conjugative plasmids by polymerase chain reaction (PCR). Sequencing of gene cassette arrays revealed that cassettes of the dfr and aadA families were most common. Within the cohort of UTI bacteria, 37% (11/30) were positive for class 1 integrons, and the dfrA17-aadA5 gene cassette array was most common. The four MBL-producers contained the gene cassette blaIMP-4 found within a class 1 integron which was responsible for the MBL phenotype. An assay based on real-time PCR was also developed to measure the recombination activity of the integron integrase (IntI) enzymes. The existing method of IntI measurement, the in vivo conduction assay, was used as a basis for the development of the real-time PCR assay. Five 59-be from the gene cassettes aadB, orfA, sat2, dfrA1 and aacA4 were cloned as recognition sites used in the real-time PCR assay. IntI1 was the most active integrase and showed an activity of 2.31 ?? 10??-1 when recombining the aadB and orfA 59-be. The highest level of class 2 integrase activity was 2.00 ?? 10-1?? during recombination of the sat2 and dfrA1 59-be, while IntI3 showed its highest recombination frequency of 2.29 ?? 10-1?? when the aadB and orfA 59-be were used. Additionally, the real-time PCR assay was used assess the levels of IntI activity over time. Using this method, the level of recombination as time progressed remained stable at a level of 4.10 ?? 10-2????. MDR was also analysed in 37 Acinetobacter baumannii isolates which were collected from four hospitals in Sydney. Minimum inhibitory concentration (MIC) analysis to 25 antibiotics revealed that all isolates showed a reduced susceptibility to between five and 24 antibiotics. PCR was performed to detect the presence of resistance determinants. Class 1 integrons encoding resistance to aminoglycosides, antiseptics and disinfectants were found in 35 % (13/37) of the isolates. Aminoglycoside resistance genes including aphA1 (12/37), strA (1/37) and strB (22/39) were also found. Resistance to beta-lactams was also observed in all isolates, which correlated with the presence of the ampC and blaOXA-51-like genes. The insertion sequence ISAba1 which provides an alternative promoter leading to increased gene expression was found upstream of the ampC gene in 29 isolates; the same isolates also contained the identical insertion sequence upstream of the carbapenemase resistance gene blaOXA-23. These 29 isolates also possessed the tetracycline resistance gene tetB. All but one of these 29 isolates also contained the gene blaTEM-1. Resistance to quinolones and fluoroquinolones was attributed to the presence of a Ser83-Leu83 gyrA mutation present in 36 resistant isolates. Furthermore, a putative dihydrofolate resistance gene, folA, was found in all isolates. Repetitive extragenic palindromic PCR revealed the presence of seven clonal groups. Overall, this study demonstrated the widespread impact and dissemination of MDR within nosocomial settings in Australia. The use of new assays, such as the real-time PCR assay developed in this thesis, is essential to the understanding of dissemination of antibiotic resistance.

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Darko, Janice. « Fluorescent Labeling of Antibiotic Resistant Bacteria Model DNA ». BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7600.

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Global threats to treatment of bacterial infections due to antibiotic resistance (AR) have been on the rise in recent years. Current diagnostic tests identify bacteria by using blood culture, which takes more than 24 hours. This study focuses on the fluorescent labeling of DNA derived from bacterial AR genes (KPC & VIM) and other model DNAs using oligreen dye (OG) and molecular beacons (MB). A NanoDrop 3300 fluorospectrometer was used to take fluorescence measurements. Linear dynamic range and labeling efficiency were dependent on the following optimized conditions: dilution factor of OG (200 fold), buffer (20 mM Tris HCl, pH 8), and heat treatment of 95 °C for 15 min.Fluorescence analysis of a target DNA with a designed MB showed signal-to-background of 10 with our buffer only and 20 with our buffer and 25% ethanol. I also demonstrated a simple microfluidic device capable of detecting AR genes using model DNAs, magnetic beads, and designed MBs for assays of µ50 L volume. This study provides a first step towards detecting MB-DNA complexes by a simple, low cost, and fast non-amplified method, which may be used to detect AR genes in clinical samples in the future.

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DeSilva, Malini. « Efficacy of Print Media Risk Communication About Antibiotic Resistance ». Thesis, Boston College, 2003. http://hdl.handle.net/2345/427.

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Thesis advisor: Roche P. John
The growing threat of antibiotic resistance makes it extremely important that citizens be informed about the risks posed by antibiotic-resistant bacteria, and measures with which they can reduce these risks. The print media are major sources of such information for members of the public. In the present study, articles from major newspapers in the United States and Canada appearing between 1998 and 2002 were surveyed to determine the extent to which mention was made of antibiotic resistance and the risks associated with antibiotic resistance, the contextual precision with which this information was communicated, and the extent to which information was presented about causes, and risk-reduction measures, associated with antibiotic resistance. The majority of articles surveyed mentioned antibiotic resistance, but most failed to mention associated risks (i.e., the risk of illness and/or the risk of mortality). Articles that did report risks, did so only at a low level of contextual precision. A relatively low percentage of articles mentioned causes of antibiotic resistance, and even fewer mentioned risk reduction measures. These findings suggest that the print media could improve the efficacy with which they inform the public about issues associated with antibiotic resistance
Thesis (BS) — Boston College, 2003
Submitted to: Boston College. College of Arts and Sciences
Discipline: Biology
Discipline: College Honors Program

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Barbosa, Teresa Maria Leite Martins. « Tetracycline resistance transfer among obligate anaerobes from the ruminant gut ». Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286850.

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The main aim of this work was to investigate the nature, distribution and transmissibility of tetracycline resistance (Tc^R) genes among ruminant anaerobic bacteria. Two Tc^R rumen strains of Butyrivibrio fibrisolvens, 1.230 and 1.23, were able to transfer the resistance phenotype to the type strain, 2221^R although a third Tc^R strain, 1.210, could not. PCR amplification of 16S rDNA sequences showed that the three isolates were phylogenetically distinct from the recipient strain, but related to each other. Hybridisation work suggested the presence of two chromosomal Tc^R determinants among the B. fibrisolvens isolates. All three strains contained a non-transferable tet(O) gene, 100% identical at the nucleotide level with tet(O) from S. pneumoniae. The mobile Tc^R determinant present in strains 1.230 and 1.23, proved to be a novel ribosome protection tet gene, tet(V), whose gene product shares only 68% amino acid identity with its closest relatives, TetO/TetM and has G+C content considerably higher than that of other B. fibrisolvens genes. tet(V) was also identified in two Australian rumen B. fibrisolvens strains, in the rumen anaerobes Selenomonas ruminantium and Mitsuokella multiacidus, and in a pig isolate of M. multiacidus. These results provide evidence for gene transfer between obligate and facultative anaerobes from different gut ecosystems and different geographical locations. PFGE demonstrated that mobile chromosomal elements 40-50 kb in size, TnB1230 and TnB123, with preferred insertion sites in the recipient genome mediated the transfer of tet(V) in B. fibrisolvens. No homology was found between TnB1230 and regions from Tn916 and Tn5253. TnB1230 is not associated with tet(V) in the other bacterial strains, suggesting that a diverse range of elements carry the gene in different bacteria. Although tet(V) is chromosomally encoded in the majority of the strains examined, there is some evidence that the gene may be located in a plasmid in S. ruminantium FB32 and FB34.

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Al-Khateeb, Mohammed Jihad M. Jalal. « Investigation into the epidemiology of multi-drug resistance plasmids of hospital-associated coliform bacteria ». Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243028.

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Vasilenko, Sofia, et Софія Василенко. « Bacteria resistance to beta-lactam antibiotics ». Thesis, National Aviation University, 2021. https://er.nau.edu.ua/handle/NAU/50637.

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1. Pulok K. Mukherjee. Quality Control and Evaluation of Herbal Drugs: Evaluating Natural Products and Traditional Medicine. Elsevier, 2019. 762 p. 2. Kumar A., Schweizer H. Bacterial resistance to antibiotics: Active efflux and reduced uptake. Adv. Drug Deliv. Rev. 2005. Vol. 57. P. 513. 3. Antimicrobial Resistance: Tackling a Crisis for the Future Health and Wealth of Nations. Chaired by Jim O’Neill. London: Review on Antimicrobial Resistance. 2014. 16 p. 4. Thomas C. M., Nielsen K.M. Mechanisms of, and barriers to, horizontal gene transfer between bacteria. Nat. Rev. Microbiol. 2005. Vol. 3. P. 711–21.
Increasing antibiotic resistance of microorganisms is one of the urgent and unresolved problems in the fight against pathogenic microorganisms. Antibiotic resistance of microorganisms can be true and acquired. True resistance is characterized by the absence of the antibiotic action of the target in microorganisms or the inaccessibility of the target due to the primary low permeability or enzymatic inactivation. Acquired resistance it is the property of individual bacterial strains to maintain viability at those concentrations of antibiotics that suppress the bulk of the microbial population. The formation of resistance in all cases is due to genetics - the acquisition of new genetic information or a change in the level of expression of its own genes. The most common cause of acquired resistance is the widespread use of a particular antibiotic, and the consequence is that previously sensitive strains become resistant. Beta-lactam antibiotics - penicillins, cephalosporins have been used for the longest time in clinical practice, so the problem of resistance to them is the most serious. Let’s consider the most common reasons of antibiotic resistance development: unreasonable appointment of antibacterial drugs (ABD), mistakes in choosing the ABD, errors in the choice of the ABP dosing mode, errors associated with the duration of antibiotic therapy.
Підвищення антибіотико-резистентності мікроорганізмів є однією з термінових та невирішених проблем у боротьбі з патогенними мікроорганізмами. Антибіотична резистентність мікроорганізмів може бути вприродним і придбаним. Справжня стійкість характеризується відсутністю дії антибіотиків на мішені в мікроорганізмах або недоступність цілі за рахунок первинної низької проникності або ферментативної інактивації. Отримана стійкість це властивість окремих бактеріальних штамів для підтримки життєздатності при цих концентраціях антибіотиків, які пригнічують основну частину мікробного штаму. Формування стійкості у всіх випадках обумовлена генетикою - придбанням нової генетичної інформації або зміною рівня вираження власних генів. Найбільш поширеною причиною придбаної стійкості є широке використання конкретного антибіотика, а наслідок полягає в тому, що раніше чутливі штами стають стійкими. Бета-лактамні антибіотики - пеніциліни, цефалоспорини були використані протягом тривалого часу в клінічній практиці, тому проблема стійкості до них є найбільш серйозною. Давайте розглянемо найпоширеніші причини розвитку антибіотикорезистентності: нерозумне призначення антибактеріальних препаратів (АБД), помилки у виборі АБД, помилки у виборі режиму дозування ABP, помилки, пов'язані з тривалістю антибіотикотерапії.

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Mwansa, J. C. L. « Antibiotic resistance in salmonella and shigella in the Manchester region 1981 - 1984 ». Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378363.

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Leng, Zhongtai. « Distribution and mobility of antibiotic resistant genes in oral/urogentital [sic] bacteria ». Thesis, Connect to this title online ; UW restricted, 1998. http://hdl.handle.net/1773/9273.

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Smith, Lisa Marie. « Antibiotic resistance and coliform bacteria in the Ohio River ; 2002 to 2004 ». Huntington, WV : [Marshall University Libraries], 2006. http://www.marshall.edu/etd/descript.asp?ref=679.

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Theses (M.S.)--Marshall University, 2006.
Title from document title page. Includes abstract. Document formatted into pages: contains vii, 73 p. including illustrations and maps. Bibliography: p. 25-28.

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Wallace, Jeremy Iain. « Hyperinducible Î²-lactamase expression in gram-negative bacteria ». Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295568.

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Gullberg, Erik. « Selection of Resistance at very low Antibiotic Concentrations ». Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-235225.

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The extensive medical and agricultural use and misuse of antibiotics during the last 70 years has caused an enrichment of resistant pathogenic bacteria that now severely threatens our capacity to efficiently treat bacterial infections. While is has been known for a long time that high concentrations of antibiotics can select for resistant mutants, less is known about the lower limit at which antibiotics can be selective and enrich for resistant bacteria. In this thesis we investigated the role of low concentrations of antibiotics and heavy metals in the enrichment and evolution of antibiotic resistance. Selection was studied using Escherichia coli and Salmonella enterica serovar Typhimurium LT2 with different resistance mutations, different chromosomal resistance genes as well as large conjugative multidrug resistance plasmids. Using very sensitive competition experiments, we showed that antibiotic and heavy metal levels more than several hundred-fold below the minimal inhibitory concentration of susceptible bacteria can enrich for resistant bacteria. Additionally, we demonstrated that subinhibitory levels of antibiotics can select for de novo resistant mutants, and that these conditions can select for a new spectrum of low-cost resistance mutations. The combinatorial effects of antibiotics and heavy metals can cause an enrichment of a multidrug resistance plasmid, even if the concentration of each compound individually is not high enough to cause selection. These results indicate that environments contaminated with low levels of antibiotics and heavy metals such as, for example, sewage water or soil fertilized with sludge or manure, could provide a setting for selection, enrichment and transfer of antibiotic resistance genes. This selection could be a critical step in the transfer of resistance genes from environmental bacteria to human pathogens.

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Erlandsson, Marcus. « Surveillance of Antibiotic Consumption and Antibiotic Resistance in Swedish Intensive Care Units ». Doctoral thesis, Linköping : Univ, 2007. http://www.bibl.liu.se/liupubl/disp/disp2007/med1019s.pdf.

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Robinson, Hannah Kathleen. « Antibiotic resistance in Gram negative bacteria isolated from fish sold in Western Australia ». Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2161.

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Background Information The global misuse and overuse of antibiotics in human medicine and the animal production industry is contributing to the development of antibiotic resistance in bacteria. This is a serious threat to modern medicine and public health. Antibiotic resistant organisms can cause severe infections in humans which are difficult to treat, and in some cases impossible to resolve which can lead to premature death. Several studies have been conducted across the globe to assess the use of antibiotics in the seafood industry and the associated health risks, however, limited studies have recently explored this risk in an Australian setting. Aims This thesis aimed to investigate the presence of antibiotic residues in seafood sold in Western Australia. Furthermore, the occurrence of antibiotic resistance in Gram negative bacteria isolated from fish sold in Perth, Western Australia was assessed. The impact of country of origin on the presence of antibiotic residues and antibiotic resistant bacteria in seafood samples has also been considered. Methodology Historical data was accessed from the Local Health Authorities Analytical Committee regarding the presence of eight antibiotic types in 253 seafood samples purchased throughout Western Australia between May and June 2017. Forty-four fish samples, a mix of local and imported from Asian countries, were sourced from retail shops located in the metropolitan area of Perth between September and November 2017. Gram negative bacteria were isolated by homogenisation of the fish with a Luria Bertani Broth and incubation on media selective for Gram negative bacteria. A series of preliminary microbial identification tests were conducted on selected bacterial isolates. Matrix Assisted Laser Desorption Ionization-Time of Flight confirmed the identification of the bacteria to species level. The identified bacteria (n = 35) were analysed for antibiotic susceptibility to eight antibiotic types using the standard disc diffusion method. Results The majority of seafood samples were free from antibiotic residue contamination and compliant with Australian legislation. A single non-compliant sample contained antibiotic residues below the level required to pose an immediate health risk to the consumer. This result suggests the Australian consumer has limited risk of consuming antibiotic residues in seafood. Thirty-five Gram negative bacterial isolates from ten genera were identified. The majority of the antibiotic resistance observed in the bacteria was either explained by intrinsic resistance or was similar to previous reports. Potential acquired antibiotic resistance was observed in four Acinetobacter species and a Rhizobium isolate which were isolated from commonly farmed fish from Australia (n = 1), China (n = 1) and Vietnam (n = 3). It is possible the fish may have been exposed to antibiotics during the production cycle. However, this result must be read with caution since there are limited standardised breakpoint guidelines for these particular species and, therefore the results were inferred using guidelines for other, similar, bacterial species. From these results, it appears that there is limited risk to consumer health from exposure to antibiotic resistant bacteria via consumption of seafood, however, only a limited number of samples were assessed, and Gram positive bacteria were not evaluated in this study. These results are reassuring but suggest that vigilance is required to ensure that the risk to consumers is minimised. Where antibiotics are used inappropriately in environmental settings, the risk of environmental bacteria developing further antibiotic resistance will remain. Routine surveillance of antibiotic resistance in pathogenic bacteria in domestic and imported food of animal origin is recommended to monitor this potential risk to human public health.

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Knecht, Camila Ayelén [Verfasser], et Heinz [Gutachter] Köser. « Fate of antibiotic resistant bacteria and antibiotic resistance genes in constructed wetlands / Camila Ayelén Knecht ; Gutachter : Heinz Köser ». Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1219966215/34.

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Tlachac, Monica. « Tackling the Antibiotic Resistant Bacteria Crisis Using Longitudinal Antibiograms ». Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1318.

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Antibiotic resistant bacteria, a growing health crisis, arise due to antibiotic overuse and misuse. Resistant infections endanger the lives of patients and are financially burdensome. Aggregate antimicrobial susceptibility reports, called antibiograms, are critical for tracking antibiotic susceptibility and evaluating the likelihood of the effectiveness of different antibiotics to treat an infection prior to the availability of patient specific susceptibility data. This research leverages the Massachusetts Statewide Antibiogram database, a rich dataset composed of antibiograms for $754$ antibiotic-bacteria pairs collected by the Massachusetts Department of Public Health from $2002$ to $2016$. However, these antibiograms are at least a year old, meaning antibiotics are prescribed based on outdated data which unnecessarily furthers resistance. Our objective is to employ data science techniques on these antibiograms to assist in developing more responsible antibiotic prescription practices. First, we use model selectors with regression-based techniques to forecast the current antimicrobial resistance. Next, we develop an assistant to immediately identify clinically and statistically significant changes in antimicrobial resistance between years once the most recent year of antibiograms are collected. Lastly, we use k-means clustering on resistance trends to detect antibiotic-bacteria pairs with resistance trends for which forecasting will not be effective. These three strategies can be implemented to guide more responsible antibiotic prescription practices and thus reduce unnecessary increases in antibiotic resistance.

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Lancaster, Holli Louise. « The persistence and genetic support of genes encoding antibiotic resistance in oral bacteria ». Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444918/.

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Antibiotic-resistant bacteria present a serious public health threat and studies investigating the prevalence of antibiotic-resistant bacteria and the genes encoding for antibiotic resistance (GEAR) are essential. Such studies help us to understand how antibiotic-resistant bacteria and GEAR are obtained, transferred and maintained within a population. The aim of this study was to identify the prevalence and maintenance of antibiotic-resistant bacteria in the oral microbiota of children aged 4-6 years who had not previously taken antibiotics. Bacteria resistant to penicillin, ampicillin, tetracycline and erythromycin were widespread among the children studied. Tetracycline-resistant bacteria were found in 98% of the children sampled and the tetracycline resistance determinants most responsible for this resistance were tet(M) and tet(W). The tetracycline-resistant bacteria were maintained within 15 children over a period of twelve months. In three of these children the tet(M) gene was found to persist in a variety of genera and this was found to be contained within a Tn9/6-like element by Southern blot analysis. The tetracycline resistance determinant tet(S) was found for the first time in Streptococcus intermedius . It was found to be transferable to Enterococcus faecalis and other Streptococcus spp. by filter matings. The tet(S) gene was shown to be present on a novel Tn9/f5-like element designated Tn97r5S. The similarities between Tn916 and Tn976S included the presence of conjugative and excision and integration modules. However the tet(M) in Tn976 had been completely replaced by tet(S) in Tn9/f5S. The gene tet(32) was also found for the first time in Streptococcus parasanguinis and Eubacterium saburreum, previously it had been found in a human colonic bacterium K10. The upstream region of the oral tet(32) gene in E. saburreum 41.2T.2 was found to be more closely related to upstream sequences of tet(W) in Roseburia sp. A2-123, upstream sequences of tet(W) within TnB1230 (originally isolated from Butyrivibrio fibrisolvens ) and orf!4, orf25 and orf26 from Tn5397. This work provides further evidence that antibiotic-resistant bacteria are prevalent in the oral microbiota of children and that the genes responsible, especially those encoding resistance to tetracycline, can be maintained in the oral microbiota even when the children have not been directly exposed to antibiotics. These findings show that tetracycline resistance determinants can be mosaic in structure and can be easily transferred due to their containment within conjugative transposons. Such elements then undergo evolutionary changes, whereby recombination of the conjugative transposon modules result in new genetic elements.

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Olofsson, Sara K. « Relation Between Drug Exposure and Selection of Antibiotic Resistant Bacteria ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Univ.-bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7197.

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35

Ozaktas, Tugba. « Multiple Antibiotic Resistance Of Surface Mucus Dwelling Bacterial Populations In Freshwater Fish ». Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609113/index.pdf.

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Surface mucus of a freshwater fish, Alburnus alburnus (bleak), caught from Lake Mogan, situated in south of Ankara, was collected in different seasons. The total cultivable bacteria were enumerated by spread plate method on nine different media. Bacteria were isolated based on colony morphologies and pigmentation. A total of sixty bacterial isolates obtained. The mucus-dwelling bacteria were first tested for resistance against ampicillin and kanamycin
then streptomycin and chloramphenicol were added to the experimental set up. The resistance levels of isolates were determined in terms of four antibiotics by tube dilution method. About 90% of the isolates were resistant to chloramphenicol, about 84% to kanamycin, about 88% to streptomycin and about 98% to ampicillin. These high levels of antibiotic resistance are rather interesting from a standpoint that the lake has no record of antibiotics exposure of any sort. The plasmid isolations were carried out to determine if the multiple antibiotic resistance could be attributed to plasmids for starting assumption. But we found no direct relationship between the presence of plasmids and multiple antibiotic resistance. Our study indicated that multiple antibiotic resistance at high levels is among the current phenotypes of the fish mucus-dwelling bacterial populations in Lake Mogan.

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Levengood, Enjolie. « The effect of combined sewer overflows on the abundance of antibiotic resistance genes and bacteria in the James River ». VCU Scholars Compass, 2017. https://scholarscompass.vcu.edu/etd/5179.

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Antibiotic resistance is a major threat to human health. Clinical situations are the main focus for antibiotic resistance research, but understanding the spread of resistance in the environment is also vital. A major contributor to this spread is wastewater from combined sewer overflow (CSO) events. The effect of CSO events on antibiotic resistance in the James River near Richmond, Virginia was studied using genomic and microbiological approaches. The abundance of genes associated with resistance to quinolones (qnrA) and tetracycline (tetW) was strongly correlated with the presence of fecal indicator bacteria (E. coli abundance) as well as total nitrogen and phosphorus loads, which suggests an anthropogenic source of these genes. Abundance of the blaTEM gene, which confers resistance to β-lactam antibiotics, was elevated during CSO events and increased with precipitation and river discharge. Bacteria isolated during a CSO event were resistant to more antibiotics and had higher multi-drug resistance when compared to isolates from a non-event. This study demonstrated that CSO events are contributing to the spread of antibiotic resistance.

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BERTINI, ALESSIA. « Plasmid-mediated antimicrobial resistance in Gram-negative bacteria ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/641.

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L’epidemiologia dei plasmidi di resistenza è il principale mezzo per descrivere la diffusione delle resistenze agli antimicrobici. L’identificazione di plasmidi correlati associati a specifici geni di resistenza può aiutare a tracciare la disseminazione di plasmidi epidemici, aprendo nuovi scenari epidemiologici sui meccanismi di diffusione delle resistenze agli antimicrobici. Questo aspetto è particolarmente evidente quando si considerano plasmidi che sono associati alla diffusione delle Beta Lattamasi a Spettro Esteso (ESBL) come gli enzimi CTX-M, SHV, TEM. Lo scopo di questa tesi è stato quello di caratterizzare plasmidi che conferiscono resistenza a farmaci rilevanti per la terapia umana in differenti collezioni di Enterobacteriaceae di origine umana e animale. Verranno discussi diversi esempi di plasmidi epidemici quali: i plasmidi IncHI2 che trasportano i geni blaCTX-M-9 o blaCTX-M-2 provenienti da isolati di origine umana e animale di Escherichia coli e Salmonella dalla Spagna, Belgio e Inghilterra; i plasmidi IncI1 caratterizzati da specifici fattori di virulenza, che trasportano i geni blaTEM-52 e blaCTX-M-1 derivanti da isolati di Salmonella e E. coli di origine umana e animale; i plasmidi IncN che trasportano i geni codificanti la metallo-β-lattamasi VIM-1 da isolati umani di Klebsiella pneumoniae and E. coli dalla Grecia; plasmidi IncA/C2 associati a specifici geni di resistenza come blaCMY-2, blaCMY-4, blaVIM-4 e blaVEB-1 provenienti da diverse Enterobacteriaceae isolate in differenti parti del mondo, ed infine, i plasmidi associati all’enzima SHV-12 isolati in diverse Enterobacteriaceae di origine umana e animale. L’analisi mediante comparazione della struttura plasmidica ha permesso di rilevare la diffusione di plasmidi emergenti e consente di tracciare i percorsi evolutivi e di diffusione attraverso l’acquisizione di una vastità di elementi genetici mobili associati ai geni di resistenza.
The epidemiology of resistance plasmids is a major issue for the description of antimicrobial resistance diffusion. The identification of related plasmids associated to specific resistance genes may help to follow the spread of epidemic plasmids, opening new epidemiological scenarios on the mechanism of diffusion of antimicrobial resistance. This aspect is particularly interesting when applied to collections of plasmids that are playing a major role in the diffusions of Extended Spectrum Beta Lactamases (ESBLs) such as CTX-M, SHV, TEM. The aim of this thesis is the molecular characterization of plasmids conferring drug resistances in different collections of Enterobacteriaceae of human and animal origin. Several example of epidemic plasmids will be discussed: the IncHI2 plasmids carrying blaCTX-M-9 or blaCTX-M-2 genes identified from human and animal isolates of Escherichia coli and Salmonella from Spain, Belgium and UK; the IncI1 family of plasmids characterized by specific virulence factors, carrying the blaCMY-2, blaTEM-52 and blaCTX-M-1 genes from Salmonella and E. coli of human and animal origin; the IncN plasmids carrying the gene codifying the metallo-β-lacatamase VIM-1 from human isolates of Klebsiella pneumoniae and E. coli in Greece; the IncA/C2 plasmids carrying specific resistance genes such as blaCMY-2, blaCMY-4, blaVIM-4 and blaVEB-1 from different Enterobacteriaceae isolated worldwide; different plasmid replicons (IncFII, IncA/C1, IncI1) carrying the ESBL SHV-12 from human and animal origin. The comparative analysis of plasmid backbones allowed to ascertain the diffusion of common, emerging plasmids and helped to determine the evolution of these plasmids by acquisition of relevant resistance genes by a panoply of mobile genetic elements and illegitimate recombination events.

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Woodford, Jennifer. « The Threat of Antibiotic Resistant Bacteria : The Role of EF-P and EpmA in Antibiotic Resistant E. coli ». Ohio Dominican University Honors Theses / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=oduhonors1620140308432787.

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El, Salabi Allaaeddin Ali. « Characterisation of antibiotic resistance mechanisms in Gram-negative bacteria from Tripoli and Benghazi, Libya ». Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/55122/.

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As very little information is known of the antibiotic resistance in Gram-negative bacteria in Libya in addition to the desperate need for insight knowledge of the antibiotic resistance in Libyan hospitals, this study was undertaken to investigate the mechanism of antibiotic resistance in isolates collected from clinical, non-clinical and environmental samples from Tripoli and Benghazi, Libya. Bacterial collection include samples taken from patients admitted to the hospitals in ICUs and other wards, they also include swabs randomly collected from hospitals environment. These swabs were from walls, bedsides, curtains, floors, toilets, workstations, mechanical ventilators, stainless steel containers and instruments used in particular ICUs. This study clearly demonstrates the emergence of MDR Gram-negative bacteria in Tripoli and Benghazi hospitals, these MDR bacteria were clinical and non clinical revealing the long standing infection control problem in these hospitals. K. pneumoniae was found as the most frequently isolated strain being disseminated in hospitals and outside hospitals followed by E. coli. K. pneumoniae and E. coli were detected harbouring blacjx-M group 1 in association with ISEcpl the enhancer of the p-lactamase gene movement. More importantly, &/ ctx-m-i5 in association with ISEcpl were detected carried on conjugative plasmids of different sizes and able to move via Libyan K. pneumoniae and E. coli to sensitive bacteria via conjugation. Some isolates of K. pneumoniae were clonally related and were in some cases found in different hospital revealing the outbreak of MDR K. pneumoniae in Libyan hospitals. E. coli strains showed the emergence of more than one clone in one hospital which indicates to the lack of hospital hygiene. Three novel sequence types among K. pneumoniae were discovered in this study, one of which K. pneumoniae AES817 that assigned ST511 was collected from one of Benghazi streets and was found carrying blacrx-M-is and ISEcpl on a plasmid of 400kb. Characterisation of P. aeruginosa showed the emergence of clonally related strains carrying blaym-i, one was isolated from a patient admitted to Al-Jalla hospital in Benghazi and the other from a stainless steel container from the same hospital but different ward, this MBL was found on a novel integron in both strains. Interestingly, 6/A. xylosoxidans, it is moreover the first MBL discovered in Libya.

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Sharkey, Liam Karl Robert. « Functional insights into ABC-F proteins that mediate antibiotic resistance in Gram-positive bacteria ». Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12924/.

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Members of the ABC-F subfamily of ATP-binding cassette (ABC) proteins mediate resistance to a broad array of clinically-important antibiotic classes that target the ribosome of Gram-positive pathogens. The mechanism by which the ABC-F proteins mediate antibiotic resistance is poorly defined, although two hypotheses have been proposed; drug efflux and ribosomal protection. Here, this mechanism of resistance was investigated using a combination of bacteriological and biochemical techniques. Results obtained from the bacteriological assays provided preliminary data in support of ribosomal protection. Subsequently, the heterologous expression and purification of two ABC-F proteins, Vga(A) and Lsa(A), allowed the function of these proteins to be assessed in staphylococcal transcription-translation (T/T) reactions. Addition of Vga(A) and Lsa(A) to T/T assays subject to antibiotic inhibition caused drug specific, dose-dependent, rescue of translation. Several previously described resistance phenotypes attributed to these proteins were successfully recapitulated in T/T assays, corroborating the idea that rescue of translation observed in vitro is representative of the action of these proteins in whole cells. Finally, ribosome binding assays showed Lsa(A) to be capable of displacing antibiotics from staphylococcal ribosomes. Collectively, the experiments described in this thesis provide the first direct evidence to support a mechanism of ARE ABC-F resistance based on ribosomal protection.

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Norgren, Benjamin. « What role does aquaculture play in the global rise of antibiotic-resistant bacteria ? » Thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-182602.

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In a world where the human population is increasing, new innovations to produce enough food are required. Aquaculture’s part of the global animal protein production has increased in recent years and could be a possible solution. However, if aquaculture is poorly managed, it can result in negative consequences and one such consequence is the development of antibiotic resistance. In this review, I examine how aquaculture affect antibiotic resistance by studying what the literature says on accumulation of antibiotics in different organisms and sediment, if antibiotics can be transferred to humans through consumption of antibiotic treated products, and if human pathogens in aquaculture farms may acquire antibiotic resistance. Furthermore, I examine what factors are contributing to irresponsible antibiotic use and how such use is managed. The result of this review indicate that antibiotics are able to accumulate in organisms and sediment. It is not clear however how consumption of these affect human microbiomes. In contrast, it is clear that antibiotic resistance can be transferred from antibiotic-resistant bacteria to human pathogens. Regarding antibiotic use, irresponsible use foremost exists in low-income countries and the main drivers behind such use are socioeconomic ones, such as lack of knowledge, poverty and food security. Finally, I propose possible solutions that might improve future management.
I en värld där den mänskliga befolkningen ökar krävs nya innovationer för att producera tillräckligt med mat. Vattenbrukets andel av den globala animaliska proteinproduktionen har ökat de senaste åren och kan ses som en potentiell lösning. Om vattenbruk dock hanteras ansvarslöst kan det uppstå negativa konsekvenser. En sådan konsekvens är utveckling av antibiotikaresistens hos skadliga bakterier. I denna litteraturstudie undersöker jag vattenbrukets påverkan på antibiotikaresistens genom att studera vad litteraturen säger om ackumulation av antibiotika i olika organismer och sediment, om antibiotika kan överföras till människor genom konsumtion av antibiotikabehandlade produkter, och om mänskliga patogener i vattenbruksodlingar kan förvärva antibiotikaresistens. Jag undersöker också vilka faktorer som bidrar till ansvarslös antibiotikaanvändning och hur den hanteras ur ett hållbarhetsperspektiv. Resultaten i denna studie tyder på att antibiotika kan ackumuleras i organismer och sediment men att det råder oklarheter huruvida konsumtion av antibiotikabehandlad mat påverkar mänskliga bakteriekulturer. Antibiotikaresistens kan dock överföras från antibiotikaresistenta bakterier till mänskliga patogener. Ansvarslös antibiotikaanvändning sker huvudsakligen i fattigare länder och det är förmodligen i stor utsträckning till följd av socioekonomiska faktorer som okunskap, fattigdom och livsmedelstrygghet. Slutligen föreslår jag lösningar som möjligen kan bidra till bättre hantering av framtida antibiotikaanvändning.

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Ferro, Giovanna. « Wastewater disinfection by AOPs : effect on antibiotic resistance and contaminants of emerging concern ». Doctoral thesis, Universita degli studi di Salerno, 2016. http://hdl.handle.net/10556/2473.

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Pulido, Natalie Anne. « Effect of Standard Post-harvest Interventions on the Survival and Regrowth of Antibiotic-Resistant Bacteria on Fresh Produce ». Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/83528.

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Raw vegetables can sometimes be the source of outbreaks of human illness; however the potential for fresh vegetables to serve as a vehicle for antibiotic -resistant bacteria is poorly understood. Antibiotics and antibiotic-resistant bacteria have been shown to persist in manure of animals administered antibiotics, and in compost generated from this manure, where there is the potential for their transfer to produce. The purpose of this study was to determine the survival of antibiotic-resistant bacteria on raw, peeled, carrots after washing with commonly used chemical sanitizers. Multi-drug resistant E. coli O157:H7 and Pseudomonas aeruginosa were inoculated into a compost slurry of composted manure from dairy cattle, with and without prior administration of antibiotics, and used to inoculate carrot surfaces prior to the washing studies. This approach provided defined model antibiotic-resistant pathogens present within a background microbial community simulating potential carry over from manure-derived fertilizer. Carrots (n=3, 25g) were air-dried and stored at 4 °C until washing with tap water, XY-12 (sodium hypochlorite, 50 ppm free chlorine) or Tsunami 100 (peroxyacetic acid/hydrogen peroxide, 40 ppm free paracetic acid), according to manufacturer's directions. A second batch of carrots representing each inoculation x wash condition (n=3) were individually packaged for storage at 2 °C for 1,7, and 14 days, or 10 °C for 7 days and enumerated on those day intervals to recover bacteria from the surfaces of washed carrots. The resulting previously washed and stored carrots were subject to serial dilution and plated onto corresponding agar to enumerate total aerobic bacteria (R2A), aerobic bacteria tolerant or resistant to antibiotics (antibiotic-supplemented R2A), E. coli (Eosin Methylene Blue), and Pseudomonas spp. (Pseudomonas Isolation Agar). In addition, the tetA gene was quantified from the carrot samples as a measure of the effect of sanitizers and storage on an antibiotic resistance gene known to be carried by the inoculated bacteria.Inclusion of sanitizer in the wash water significantly reduced the absolute numbers of inoculated bacteria (E.coli and Pseudomonas) as well as populations of bacteria capable of growth on the R2A media containing cefotaxime (10μg/mL), sulfamethoxazole (100μg/mL), or tetracycline (3μg/mL). Comparable reductions in the inoculated P. aeruginosa resistant to tetracycline (PIA T, 4μg/mL), bacteria resistant to cefotaxime (10μg/mL) and tetracycline (3μg/mL) occurred after washing with XY-12 or Tsunami 100. The sanitizer effectiveness may be bacterial dependent, as evident by larger absolute reductions of the inoculated E. coli (EMB) and bacteria grown on sulfamethoxazole (100μg/mL)-amended plates after washing with Tsunami 100 compared to washing with tap water or XY-12. Re-growth of both the inoculated and native compost-associated bacteria was inhibited by storage at 2 °C, as there were no significant differences in the log CFU/g values on the various media (total aerobic bacteria, bacteria on antibiotic-amended plates, E. coli inoculum, P. aeruginosa inoculum) during the 14-day storage period. However, temperature abuse at 10 °C resulted in significant re-growth of native Pseudomonas, compared to storage at 2 °C. A sanitizer-associated interaction between re-growth and temperature was also observed for bacteria resistant to clindamycin (25μg/mL) and cefotaxime (10μg/mL), with substantial re-growth occurring only on carrots washed with Tsunami 100. There was no significant re-growth of the inoculated E. coli O157:H7 at either temperature. Results indicate that some bacterial populations are reduced by post-harvest washes and that temperature abuse of fresh produce may result in increases in antibiotic-resistant bacterial populations.
Master of Science in Life Sciences

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Van, Thi Thu Hao, et thuhao2007@gmail com. « Detection of Enteric Bacteria in Raw Food Samples from Vietnam and Evaluation of Antibiotic Resistance ». RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090407.141836.

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This study was conducted to examine the rate of contamination and molecular characteristics of enteric bacteria isolated from a selection of food sources in Vietnam. One hundred and eighty raw food samples were tested and 60.8% of meat and 18.0% of shellfish samples were found to be contaminated with Salmonella spp. which belonged to variety of serogroups and serotypes. More than 90% of all food sources contained Escherichia coli and 32% of 50 shellfish samples were contaminated with Vibrio parahaemolyticus. PFGE was used to determine the degree of relatedness of Salmonella spp. There were 33 distinct PFGE patterns from 51 Salmonella spp. isolates tested, indicating that PFGE could be used as an alternative method for serotyping for use in epidemiology of Salmonella spp. Susceptibility of the isolates to 15 antimicrobial agents was investigated. Moderate to high frequencies of resistance to antibiotics were observed in Salmonella spp. and E. coli isolates and multi-resistance, defined as resistance to at least 4 antibiotics, was observed. All of the V. parahaemolyticus isolates were resistant to ampicillin/amoxicillin but not to other antibiotics. Betalactam TEM gene and tetracycline resistance tetA, tetB genes were widely distributed in both E. coli and Salmonella spp. isolates. Other resistance genes, including sulI, cmlA, aadA, aphA1, dhfrV, and aac(3)-IV were also present at high to moderate levels. Identification and characterisation of the mobile genetic elements, including identification of class 1 integrons and plasmids were carried out for multi-resistance isolates. The integrons harboured varying gene cassettes, including aadA1, aadA2, aadA5, aacA4, dhfrXII, drfA1 and dhfrA17, blaPSE1 and catB3. Thirty-five percent of Salmonella spp. isolates and 76% of E. coli isolates harboured plasmids of more than 95 kb. Transfer of resistance phenotypes between the isolates via conjugation and phage transduction was also demonstrated. Salmonella genomic island 1 (SGI1), a 43-kb genomic region contains a 13-kb antibiotic resistance gene cluster, has been identified in an isolate of S. Albany from chicken. The presence of Salmonella spp. virulence genes was investigated to examine the pathogenicity potential of the isolates. The invA gene was present in all Salmonella spp. isolates and the plasmid virulence gene spvC was detected in one S. Typhimurium isolate only, on a 95 kb virulence plasmid. Invasion assays performed in vitro demonstrated that all Salmonella isolates were capable of invading human intestine INT407 cells. In addition, the investigation for the presence of 58 selected virulence genes showed that all the tested isolates contained at least one virulence gene and there were 16 genes which are associated with different pathotypes detected. The data obtained in this study indicates that raw food in Vietnam is a potential reservoirs for many pathogenic organisms, and confirms the role of food animals as a reservoir of multidrug resistant E. coli and Salmonella spp.

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Heard, R. G. « An investigation of the antibiotic resistance genes in bacteria isolated from a veal calf rearing farm ». Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233597.

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Kinkelaar, Daniel Francis. « Profiles of Tetracycline Resistant Bacteria in the Human Infant Digestive System ». The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213330709.

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Redgrave, Liam Stephen. « The role of supercoiling in altering chromosome structure, gene expression and antibiotic resistance in bacteria ». Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7912/.

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Antibiotic resistance is a major problem estimated to cost $100 trillion and cause 10 million deaths per year by 2050. Despite novel molecules targeting Gram-positive bacteria, there are no new antibiotics active against Gram-negatives. To prolong use of current drugs, we need to understand mechanisms of resistance to inform prescribing practices and drug discovery. Quinolone resistance is primarily conferred by mutations in the target loci: DNA gyrase (gyrA) and topoisomerase IV. Quinolone resistance arising from gyrA mutations has also been shown to confer a low level of protection against a range of non-quinolone drugs. This thesis investigated the hypotheses that altered supercoiling levels, resulting from gyrA mutations, alter expression of stress response genes and confer a generic protective effect against other antibiotics and chemicals. The effects of equivalent gyrA mutations in Salmonella and E. coli upon supercoiling were analysed. Both GyrA Ser83Phe and GyrA Asp87Gly substitutions resulted in altered topoisomer profiles, although these were different between the species. When exposed to stresses, Salmonella gyrA mutants maintain supercoiling in a relatively fixed manner, providing a degree of antimicrobial protection but possibly limiting flexibility in response to environmental change. Fluorescent reporter assays showed a modest elevation of stress responses in Salmonella GyrA Asp87Gly cells, but highly upregulated stress responses in E. coli GyrA Asp87Gly cells. This correlated with a competitive fitness benefit of E. coli GyrA Asp87Gly cells vs the parent in the presence of low levels of triclosan. The elevated stress responses likely result from supercoiling-induced changes in promoter accessibility, and are probably responsible for the generic protective effect gyrA mutation confers against other chemicals and antibiotics. Non-quinolone antimicrobials can provide a selective pressure that favours gyrA mutants, although this is highly dependent on condition and species.

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McCarthy, Kelly A. « Exploiting Dynamic Covalent Binding for Strain-Specific Bacterial Recognition : ». Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108513.

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Thesis advisor: Eranthie Weerapana
Antibiotic resistance of bacterial pathogens poses an increasing threat to the wellbeing of our society and urgently calls for new strategies for infection diagnosis and antibiotic discovery. The overuse and misuse of broad-spectrum antibiotics has contributed to the antibiotic resistance crisis. Additionally, treatment of infections with broad-spectrum antibiotics can cause disruption to the host gut microbiome. The development of narrow-spectrum antibiotics would be ideal to avoid unnecessary cultivation of antibiotic resistance and damage to the human microbiota. Bacteria present many mechanisms of resistance, including modulating their cell surface with amine functionalities. In an age where infections are no longer responding to typical antibiotic treatments, novel drugs that target the characteristics of antibiotic resistance would be beneficial to remedy these defiant infections. Herein, we describe the utility of iminoboronate formation to target the amine- presenting surface modifications on bacteria, particularly those that display antibiotic resistance. Specifically, multiple 2-acetylphenylboronic acid warheads were incorporated into a peptide scaffold to develop potent peptide probes of bacterial cells. Further, by engineering a phage display library presenting the 2-acetylphenylboronic acid moieties, we were able to perform peptide library screens against live bacterial cells to develop reversible covalent peptide probes of target strains of bacteria. These peptide probes, which were developed for clinical strains of Staphylococcus aureus and Acinetobacter baumannii which display resistance, can label the target bacterium at submicromolar concentrations in a highly specific manner and in complex biological milieu. We further show that the identified peptide probes can be readily converted to bactericidal agents that deliver generic toxins to kill the targeted bacterial strain with high specificity. It is conceivable that this phage display platform is applicable to a wide array of bacterial strains, paving the way to facile diagnosis and development of strain-specific antibiotics. Furthermore, it is intriguing to speculate that even higher potency binding could be accomplished with better designed phage libraries with dynamic covalent warheads. This work is currently underway in our laboratory
Thesis (PhD) — Boston College, 2018
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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Qian, Leilei. « Evaluation of Antibiotic Resistance Profiles of Enteric Bacteria in Swine Feces Before and After Lagoon Treatment ». NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-05082007-161836/.

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Antibiotics are used in livestock production for the treatment of diseases and for improvement of feed efficiency and growth. However, agricultural use of antibiotics may be partly responsible for the emergence of antibiotic-resistant organisms. Large amounts of managed manure are land applied, which opens the door for the spread of antibiotic resistance in the environment. Thus, the goal of this project was to evaluate the effects of lagoon treatment on the persistence of antibiotic resistant enteric bacteria isolated from swine feces. Both cool season and warm season samples were collected from a swine farm located in Sampson County, NC. Each season samples included three nursery swine fecal samples, three nursery swine lagoon liquid samples, four finishing swine fecal samples, three finishing swine lagoon liquid samples, and four soil samples from both nursery and finishing swine spray field. A total of 4032 E. coli isolates and 4896 Enterococcus isolates were obtained from the samples. The antibiotic resistance profiles of the isolates were determined using a set of antibiotics at various concentrations. The antibiotic cephalothin, erythromycin, oxytetracycline, tetracycline, streptomycin, and neomycin were tested for both bacterial species, but different concentrations were applied. For E. coli, rifampicin was also tested; for Enterococcus, chlortetracycline, vancomycin, and amoxicillin were also tested. After antibiotic resistance analysis was achieved, 25 isolates were randomly selected from each sample for further evaluation by polymerase chain reaction test. Soil samples were collected; however, fecal indicator bacteria were not recovered. Additionally, E. coli was not recovered from warm season nursery lagoon samples. All isolates displayed multiple antibiotic resistance, and for the isolates from the same source, the resistance patterns were similar for the antibiotics within the same antibiotic family. Percentages of resistant isolates were greater in nursery fecal samples than in finishing fecal samples for majority of antibiotic tests. For nursery samples, percentages of antibiotic resistant isolates decreased after lagoon treatment for majority of antibiotic tests. For finishing samples, no such trend was obvious. The results indicated that antibiotic resistant isolates still persist in the lagoon liquid, which may cause potential risk to human and environmental health. And because antibiotic resistance may affect later therapeutic and subtherapeutic value of these antibiotics, management strategies of agricultural antibiotic use may be improved. The antibiotic resistance patterns and molecular banding patterns of the isolates were not unique to a specific source. The results suggest that there is considerable overlap among nursery feces, nursery lagoon, finishing feces and finishing lagoon samples. However, if combine of the feces and the lagoon isolates together and only classify isolates from nursery to finishing swine, the percentages of correctly classified isolates became larger. The results suggest that ARA and PCR would best be used for identifying fecal contamination from swine sources based on broad categories (nursery versus finishing) instead of relying on these procedures for specific identification of lagoon and feces separately.

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Cortado, Hanna Hifarva. « Tetracycline resistance in adult human gastrointestinal microflora can it tell the story of antibiotic resistance in humans ? / ». Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1213366360.

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Thèses sur le sujet « Antibiotic resistance bacteria (ARB) »

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