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Wright, A. "Structural changes in the human cochlea during drug treatment." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371567.
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Berninger, Erik. "Quinine as a model for the study of cochlear hearing loss in humans /." Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4272-2/.
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Chin, Alex C. "Anti-inflammatory effects of the macrolide antibiotic tilmicosin." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31336.pdf.
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El-Sabbagh, Nasser Mohamed. "Effects of dissolved carbon dioxide on antibiotic production." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415315.
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Khan, David D. "Pharmacokinetic-Pharmacodynamic modeling and prediction of antibiotic effects." Doctoral thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-282604.
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Problems of emerging antibiotic resistance are becoming a serious threat worldwide, and at the same time, the interest to develop new antimicrobials has declined. There is consequently a need for efficient methods to develop new treatments that minimize the risk of resistance development and that are effective on infections caused by resistant strains. Based on in silico mathematical models, describing the time course of exposure (Pharmacokinetics, PK) and effect (Pharmacodynamics, PD) of a drug, information can be collected and the outcome of various exposures may be predicted. A general model structure, that characterizes the most important features of the system, has advantages as it can be used for different situations. The aim of this thesis was to develop Pharmacokinetic-Pharmacodynamic (PKPD) models describing the bacterial growth and killing after mono- and combination exposures to antibiotics and to explore the predictive ability of PKPD-models across preclinical experimental systems. Models were evaluated on data from other experimental settings, including prediction into animals. A PKPD model characterizing the growth and killing for a range of E. coli bacteria strains, with different MICs, as well as emergence of resistance, was developed. The PKPD model was able to predict results from different experimental conditions including high start inoculum experiments, a range of laboratory and clinical strains as well as experiments where wild-type and mutant bacteria are competing at different drug concentrations. A PKPD model, developed based on in vitro data, was also illustrated to have the capability to replicate the data from an in vivo study. This thesis illustrates the potential of PKPD models to characterize in vitro data and their usage for predictions of different types of experiments. The thesis supports the use of PKPD models to facilitate development of new drugs and to improve the use of existing antibiotics.
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Webb, Jason Crispin John. "The Effects of Antibiotic Combinations on Bone Cement Properties." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525435.
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Wikblom, Ida. "Antibiotic Use and Effects in the Terminally Ill : – A Retrospective Review." Thesis, Örebro universitet, Institutionen för medicinska vetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-66978.
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Fisher, Morgane, (Dennison) Jaime Thomas, and Danielle Weimann. "Effects of an Educational Intervention on Parental Knowledge Regarding Antibiotic Resistance." The University of Arizona, 2008. http://hdl.handle.net/10150/624276.
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Class of 2008 Abstract<br>Objectives: To evaluate changes in parental knowledge regarding antibiotic use and antibiotic resistance with an educational intervention given at elementary school parent-teacher association (PTA) meetings.
Methods: This was an analytical pre-test/post-test study of an educational intervention given at two elementary schools in the Phoenix metro area. The primary dependent variable was a knowledge measure, calculated as a total score. The changes between the pre- and post-test total score means were compared using a dependent t-test. The a-priori alpha level used was 0.05.
Results: The study sample consisted of 25 participants. Study data were collected between September 2007 and December 2007. The mean (SD) pre- and post-test scores were 33.7 (4.4) and 40.7 (2.7), respectively (p < 0.05).
Conclusions: The educational intervention presented at elementary school PTA meetings resulted in a significant knowledge increase regarding the appropriate use of antibiotics when pre- and post-test scores were compared.
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Gbejuade, Herbert Olukayode. "The effects of antibiotic loaded bone cement combinations on bacteria biofilms." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705469.
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Gordon, C. A. "The contribution of alginate to the antibiotic susceptibility of Pseudomonas aeruginosa." Thesis, University of Brighton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384621.
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Khairallah, Ramzi. "PAA disinfection kinetics of E.coli, and its effects on antibiotic-resistance genes." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121155.
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The dissemination of antibiotic-resistant bacteria has been a great concern because of the risk it poses to our health. Although wastewater treatment plants (WWTPs) are designed to reduce the overall amount of microorganisms and contaminants present in wastewater, studies suggest that antibiotic-resistant bacteria escape the primary, secondary and tertiary treatment processes, due partially to the expression of genetic mechanisms of resistance to disinfectants. The first objective of this study was to investigate the overall environmental and intrinsic mechanisms of resistance expressed by Escherichia coli in WWTP effluents disinfected with peracetic acid (PAA) at low doses and high doses, and over different time intervals. The second objective of this study was to assess the impact of PAA on the antibiotic-resistance genetic profile of E. coli isolates that have been pre-screened for uropathogenic E.coli (UPEC) virulence. To complete the first objective, samples from a biofiltration WWTP effluent were exposed to a single PAA dose of 2 mg/L applied once for 1 hour, and intermittent-doses of 0.5 mg/L applied every 30 minutes for 2 hours, before and after filtration of the samples in the laboratory. The dose-response curves were plotted and compared for each experiment using Collins-Selleck's model. Filtration of the samples led to an overall reduction of resistance to the disinfectant in the single-dose and intermittent-doses experiments, probably because of the reduction of COD levels and elimination of particles that could have shielded the bacteria. There were no significant differences between the model parameters of the single-dose and intermittent-doses disinfection curves, hence no significant adaptive genetic mechanisms of resistance were identified. To complete the second objective, samples of biofiltration, activated sludge, and physicochemical effluent were disinfected with PAA. A molecular screening technique using PCR/ Bioplex was used to detect three of the main UPEC virulence genes (papC, cnf1, and hlyA) in E. coli isolates obtained before and after disinfection. A DNA microarray technique was used to detect the presence of 30 antibiotic-resistance genes in each positively screened isolate. The antibiotic-resistance gene frequency showed a significant decrease after disinfection. This disinfection was related to a reduction in isolates carrying resistance genes to multiple classes of antibiotics, while the isolates carrying resistance genes to a single class increased in frequency. These variations seemed to be correlated to the presence of a marker for the Tn21 transposon. This transposon is known in the literature to play a major role in the acquisition of multiple antibiotic-resistance. Thus, the loss of antibiotic-resistance after PAA disinfection could be related to SOS oxidative stress responses, which may cause the deletion of DNA fragments and mobile genetic elements carrying multiple antibiotic-resistance genes such as Tn21 transposons<br>La dissémination de bactéries résistantes aux antibiotiques pose un sérieux problème de santé publique. Des études suggèrent que les microorganismes présents dans les usines de traitement des eaux usées échappent aux traitements primaires, secondaires et tertiaires, due en partie à l'expression de gènes résistants aux désinfectants. Le premier objectif de cette étude fut d'investiguer les mécanismes globaux, environnementaux et intrinsèques de résistance exprimés par les Escherichia coli présents dans les effluents d'usines de traitement d'eaux usées, désinfectés avec de l'acide paracétique à petites et grandes doses, et sur des intervalles de temps différents. Le deuxième objectif de cette étude fut d'évaluer l'impact de l'acide paracétique sur le profil génétique de résistance aux antibiotiques des colonies d'E. coli qui furent isolées et testées positives pour la virulence UPEC. Pour compléter le premier objectif des échantillons de l'effluent provenant d'une usine de traitement des eaux usées utilisant un processus de biofiltration furent exposés à une dose unique d'acide paracétique de 2mg/L appliquée au début de l'expérience, et à des doses intermittentes de 0.5mg/L appliquées à 30 minutes d'intervalles pendant 2 heures, avant et après la filtration des échantillons en laboratoire. La filtration des échantillons mena à une réduction de la résistance au désinfectant dans les deux expériences, probablement à cause de la réduction des niveaux de DCO et l'élimination des particules pouvant protéger les bactéries. Aucune différence significative ne fut observée entre les paramètres du modèle calculés pour l'expérience à dose unique et à doses intermittentes et donc aucun mécanisme de résistance intrinsèque ne fut identifié. Pour compléter le deuxième objectif, des échantillons d'effluents provenant d'usines de traitement des eaux utilisant un processus de boues activées, de biofiltration et physicochimique furent désinfectés avec de l'acide paracétique. Une technique de dépistage moléculaire ACP/Bioplex fut utilisée afin de détecter 3 gènes de virulence UPEC (papC, cnf1 et hlyA) chez les colonies d'E. coli isolées avant et après la désinfection. Une puce à ADN fut utilisée pour détecter la présence de 30 gènes de résistance aux antibiotiques, pour chaque colonie d'E.coli qui fut isolée et testée positive pour la virulence UPEC. La fréquence des gènes résistant aux antibiotiques diminua de manière significative après la désinfection. La désinfection contribua à la réduction des E. coli possédant des gènes de résistance à plusieurs classes d'antibiotiques, tandis que la fréquence des E. coli possédant des gènes de résistance à une seule classe d'antibiotique augmenta. Ces variations semblent être liées à la présence du marqueur appartenant au transposon Tn21. Ce transposon joue un rôle majeur dans l'acquisition de résistances multiples aux antibiotiques. La diminution de la résistance aux antibiotiques après désinfection pourrait être liée à des réponses au stress oxydatif, pouvant mener à l'élimination de fragments d'ADN et d'éléments génétiques porteurs de résistances multiples aux antibiotiques comme les transposons Tn21.
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Ricker, Erica Noyes Bader. "The synergistic effects of orthogonal biofilm mitigation strategies: thermal and antibiotic treatment." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5613.
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Upon forming a biofilm, bacteria undergo several changes that prevent them from being eradicated with antimicrobials alone. These biofilms manifest as persistent infections and biofouling in the medical and industrial world, respectively, constituting an ongoing medical crisis and creating a huge financial burden. Biofilms on implanted medical devices cause thousands of patients each year to undergo multiple surgeries to explant and replace the implant, driving billions of dollars in increased health care costs due to the lack of viable treatment options for in situ biofilm eradication. Heat has been used to reliably eliminate biofilms for many years, but the temperatures employed are infeasible for many applications, particularly in vivo medical treatment. Remotely activated localized heat can be applied through a superparamagnetic iron oxide nanoparticle polymer coating when paired with an alternating magnetic field. However, there is very little known about the temperatures required to kill the biofilms and the effects of the heat in conjunction with antibiotics. To better understand the required parameters to effectively kill off bacteria in biofilms a variety of heat treatments were investigated for a variety of Pseudomonas aeruginosa biofilms grown in different conditions. Additionally, these heat treatments were combined with antibiotics to better understand any combined effects of the two orthogonal treatment plans. It was found that heat is an effective method for killing the bacteria in biofilms. Temperatures ranging from body temperature, 37 °C, to 80 °C were used to heat shock the biofilms for 1 to 30 minutes. Higher temperatures for short exposure times yielded similar results to lower temperatures for longer exposure time. Biofilms grown in different conditions did vary in their susceptibility to the heat shocks; however, at the higher temperatures the differences became negligible. Therefore, the more effective treatments were the higher temperature heat shocks with shorter exposure times to maximize bacterial cell death and minimize the potential heat transfer to the surrounding tissue. Regrowth studies indicate a critical post-shock bacterial loading (~103 CFU/cm2) below which the biofilms were no longer viable, while films above that loading slowly regrew to their previous population density. Combined treatments with antibiotics had synergistic effects for all antibiotics across a window of heat shock conditions. Erythromycin in particular, which showed no effect on the biofilm alone, decreased biofilm population by six orders of magnitude at temperatures which had no effect in the absence of antibiotics. These studies will evolve the understanding of biofilms and how to efficiently eradicate them on implant surfaces. The introduction of such a novel coating in conjunction with antibiotics could obviate thousands of surgeries and save billions of dollars spent on explantation, recovery, and re-implantation.
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Hall, Gunnar. "Bacteremia after oral surgical procedures and antibiotic prophylaxis /." Stockholm, 1998. http://diss.kib.ki.se/1998/91-628-3184-4.
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Sheldon, Christopher David. "The effects of antibiotic therapy on Pseudomonas aeruginosa in adults with cystic fibrosis." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387001.
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Zeng, Wei Rong. "Acute Effects of the Antibiotic Streptomycin on Neural Network Activity and Pharmacological Responses." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700026/.
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The purpose of this study is to find out that if antibiotic streptomycin decreases neuronal network activity or affects the pharmacological responses. The experiments in this study were conducted via MEA (multi-electrode array) technology which records neuronal activity from devices that have multiple small electrodes, serve as neural interfaces connecting neurons to electronic circuitry. The result of this study shows that streptomycin lowered the spike production of neuronal network, and also, sensitization was seen when neuronal network pre-exposed to streptomycin.
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Philips, Alyssa. "EFFECTS OF HYPERBARIC OXYGEN ON STAPYLOCOCCUS AUREUS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2328.
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Hyperbaric Oxygen Therapy (HBOT) is an old technology which has acquired value in chronic wound care. HBOT is known to promote local and systemic healing effects by improving the oxygenation of the wound tissue. The increased tissue oxygenation hastens removal of the bacterial bioburden, which allows resolution of inflammation and facilitates matrix production, cell division, and ultimately wound closure. Staphylococcus aureus is the most frequently isolated organism from Diabetic Foot Infections (DFI). Therefore, our lab chose to use the treatment paradigm of HBOT to initially look at the single species level as to how HBOT affects S. aureus. DFI are primarily polymicrobial, so the responses of bacterial communities to this therapy were also considered. Previous research focused solely on host response to HBOT, but our pilot testing indicates that HBOT also exhibits a bacterial response. Initial testing with S. aureus indicated that HBOT can create growth defects in bacteria in vitro. In preliminary experiments, our lab discovered that bacterial culture on solid medium is greatly altered under the pressure of hyperbaric oxygen. Normal robust growth and pigmentation are seen in S. aureus cultured in ambient conditions. However, when the same strain is cultured under HBOT conditions, there is a marked decrease in pigmentation and colony size. When other species were exposed to HBOT conditions, growth on solid media was significantly diminished. Interestingly, K. pneumoniae is able to grow normally under HBOT conditions. Normal air mixtures at the increased pressure do not have any discernable effect on bacterial growth, and the limiting effects of oxygen are not seen unless used at the increased pressure. In a broth macrodilution MIC assay, various antibiotics show an increase in susceptibility after exposure to HBOT. Lastly, biofilm formation is altered under HBOT conditions, further supporting a bacterial adjustment to HBOT and an altered mode of growth. In order to better understand the effects of a high pressure high oxygen environment on the bacterial bioburden, this study investigates the effects of HBOT on bacterial species comprising a chronic wound. Primary data has suggested that HBOT increases susceptibility of antibiotics, and can alter bacterial transcription to hinder growth of many organisms. We hypothesize that Hyperbaric Oxygen Therapy affects diabetic foot infections by changing the healing process via transcriptional alteration of bacterial species in the wound. Furthermore, we hypothesize that HBOT alters the efficacy of some antibiotics as well as affecting the biofilm capacity of many bacterial species.
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Ambler, Jane Elizabeth. "The effects of mutator plasmids on the frequency of mutation to nalidixic acid resistance in Escherichia coli." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307583.
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Teixeira, Jaclyn Rebecca. "Effects of Antibiotic Mixtures across Marine Intertidal Trophic Levels: Examining Environmentally-Relevant Contaminant Concentrations." PDXScholar, 2016. https://pdxscholar.library.pdx.edu/open_access_etds/3372.
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Approximately 48% of Americans use prescription drugs within each 30-day period, and there are signs this trend is increasing. Although many studies track pharmaceuticals’ fates in contaminating waterways, only fairly recent efforts have examined the potential impacts of these drugs on non-target organisms. The antibiotics sulfamethoxazole and trimethoprim, often prescribed together to treat bacterial infections, have been detected worldwide in marine and estuarine environments at concentrations up to 700-800 ng/L each. Toxic effects of these drugs have been identified in freshwater organisms, with synergistic effects observed in short-term studies of mixtures of the two; however, little research has examined possible sub-lethal and longer-term effects of antibiotics in environmentally-relevant mixture concentrations on marine organisms. I examined the long-term effects of mixtures of these two antibiotics in species of a marine system: marine microalgal species, and marine mussels, to determine whether the levels currently present in waterways affect organism health and reproduction.
Microalgal species may be among the most sensitive organisms to pharmaceutical contaminants based on ecotoxicity research. I exposed three species of marine microalgae (Isochrysis galbana, Chaetoceros neogracile, and Nannochloropsis oculata) to environmentally-relevant mixtures of sulfamethoxazole and trimethoprim and examined their three-week growth rates. I found that for each species, the antibiotic treatments significantly suppressed algal growth. Specifically, I found that sulfamethoxazole was a driving factor in suppression of C. neogracile and I. galbana growth, while N. oculata responded more sensitively to a broader range of treatment mixture levels, which also included trimethoprim-only treatment groups and mixtures. These results on marine microalgae address critical data gaps, and identify the impacts of pharmaceuticals on marine primary producers, which could have direct ecosystem implications to higher trophic levels.
Antibiotic pharmaceuticals can also affect marine mussel health, based on previous study of sub-cellular endpoints. I hypothesized that the important benthic foundational species, the Mytilus californianus mussel, would be significantly impacted by long-term 12-week exposure to environmentally-relevant concentrations and mixtures of sulfamethoxazole and trimethoprim. Specifically, I measured growth rate, feeding rate, condition index, and gonando-somatic index as indicators of whole-organism and reproductive health. Sulfamethoxazole concentrations, in particular, and trimethoprim to a lesser extent, suppressed mussel growth and significantly affected condition index and gonandosomatic index over time. The results of this study offer an understanding of how an intertidal system responds to chronic presence of antibiotic mixtures in the water, and a more complete picture of the environmental consequences of pharmaceutical contaminants released into marine ecosystems at ever-growing rates.
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Hedin, Matthew Lowell. "The Effects of dairy cattle antibiotics on soil microbial community cycling and antibiotic resistance." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83227.
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Antibiotic use in agricultural ecosystems has the potential to increase resistance to antibiotics
in soil microbial communities since 40-95% of an antibiotic dose administered to livestock is
excreted intact or as metabolites. Exposure to antibiotics is also known to alter microbial
community composition, biomass, and physiology, but the potential influences of antibiotic
residues on the essential ecosystem processes that microbes regulate, e.g., carbon and
nitrogen cycling are not well understood. I investigated the effects of antibiotic residues
associated with dairy cattle operations on soil microbial communities and the ecosystem
processes they regulate. I examined the effects of antibiotic exposure on the biogeochemical
functioning of soil microbial communities by measuring the activity of extracellular enzymes
associated with organic matter processing and nutrient mineralization in soils collected from
dairy cattle operations across the United States. At each experimental station paired sites
were identified by local managers that represented sites with high and low stocking rates of
dairy cows who had been treated prophylactically with antibiotics to prevent mastitis.
Responses varied among individual enzymes, but I found an overall significant decrease in total
hydrolytic enzyme activity under high cattle stocking rates indicating a change in the
functioning of the microbial community in soils exposed to antibiotic laden manure. Principle
components analysis suggest that while some of the variation in enzyme activities are
associated with the abundance of antibiotic resistance genes, soil organic matter (total organic,
mineralizable, and particulate organic carbon) was the most significant variable accounting for
differences in enzyme activities. This reflects an inherent challenge in studies of antibiotic
exposure in agricultural landscapes: the difficulty of distinguishing direct effects of antibiotic
residues from the organic matter and nutrient subsidy associated with manure applications. To
address this concern I conducted a series of incubation experiments manipulating soils to
isolate the influences of antibiotics, manure resource subsidies, and bovine microbiome
inoculants into soils. Specifically, I examined soil respiration and antibiotic resistance gene
counts using qPCR following treatment with cephapirin, pirilimycin and a positive and negative
control. I found that pre-exposure to antibiotics and manure is important in modulating the
response of microbial communities (soil respiration, and gene copy numbers of AmpC and
TetO) to further antibiotic exposure. I conclude that antibiotics themselves have a direct effect
on soil communities and their functioning that is additive to the effect of manure (i.e., as a
resource subsidy). This effect is mediated by the history of previous exposure to antibiotics, i.e.,
cattle stocking density. These results suggest that antibiotic residues from dairy cattle
operation may have significant effects on microbial communities and the biogeochemical
cycling they regulate in agricultural ecosystems.<br>Master of Science
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Madden, G. F. J. "The effects of probiotic supplementation on the response of the intestinal microflora to antibiotic therapy." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637973.
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Much of this work involves the assessment of the effects of probiotic supplementation on the composition of antibiotic disrupted intestinal microfloras. In a double blind, placebo controlled clinical trial of patients undergoing <I>Helicobacter pylori</I> eradication therapy the effects of a probiotic comprising <I>Lactobacillus acidophilus </I>and <I>Bifidobacterium longum </I>on the faecal flora were compared. After antibiotic therapy, no change was observed among the numbers of anaerobes but the aerobic numbers increased in the antibiotic alone group; numbers of aerobes (enterobacteria) decreased in the antibiotic/probiotic group. Aerobic numbers for the probiotic re-growth population were significantly lower than the starting populations. This did not occur in the antibiotic group. In a second trial, the caecal and faecal microflora of irritable bowel syndrome (IBS) patients were compared with healthy subjects (n=8 and n=7, respectively). The composition of the caecal and faecal microfloras was comparable but numbers were lower for the caecal biopsies and caecal lumen samples. For the IBS patients, the faecal anaerobe numbers were lower than for the normal subjects and lactobacilli were not detected. The caecal samples of the IBS patients had higher numbers of aerobes than the normal subjects; lactobacilli were detected in these samples. The IBS patients were divided into two groups to receive antibiotic therapy with or without probiotic supplementation. The numbers of caecal anaerobes decreased in the antibiotic alone group but increased in the probiotic group whereas numbers of aerobes increased in both groups. Antibiotic treatment of the IBS patients favoured yeast proliferation (detected in 50% caecal samples and 75% faecal samples) but in the probiotic group, yeast growth was less abundant - only detected in 25% faecal samples.
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Beach, Justin. "An Examination of the Inhibitory Effects of Antibiotic Combinations on Ribosome Biosynthesis in Staphylococcus aureus." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/2287.
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Bacteremia initiated by Staphylococcus aureus infections can be a serious medical problem. Although a number of different antibiotics are used to combat staphylococcal infections, resistance has continued to develop. Combination therapy for certain infections has been used to reduce the emergence of resistance when a single agent has become ineffective. We hypothesize that the use of rifampicin and ciprofloxacin in combination with azithromycin, known for its inhibitory effects on the bacterial ribosome, can create potential synergistic effects resulting from indirect effects on ribosomal subunit synthesis.
To determine this we measured the effects of single and multiple antibiotics on cell growth rates, cell viability, and synthesis rates for DNA, RNA, and protein. We then measured synthesis rates of ribosomal subunits and the amounts of gyrase and RNAP. Effects of the antibiotic combinations on 70S ribosomes was assayed and the amounts of RNA and degradation was measured. We lastly studied the effects of these antibiotic combinations on mutation frequency in Staphylococcus aureus.
Our data have shown support not only for the use of antibiotic combination therapy but have provided strong evidence of an increase in the inhibition of bacterial ribosome assembly in Staphylococcus aureus. The reduction of 50S ribosomal subunit synthesis and 23S ribosomal RNA in cells grown in the presence of azithromycin, already known for it’s inhibitory effects on the 50S subunit synthesis, in combination with rifampicin or in combination with rifampicin and ciprofloxacin was observed. This also resulted in a reduction or elimination in the frequency of resistant cells when grown in the presence of these combinations.
These studies have shed light on the mechanism of action involved and synergistic effects occurring in combination antibiotic treatments and how ribosomal subunit assembly is affected. The insights gained through this research provide necessary information needed for the design of more potent antibiotic combinations. This will create a better understanding and new methods for eliminating the spread of harmful pathogens such as Staphylococcus aureus.
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Gast, Richard K. "The effects of antibiotic administration on the proliferation and interspecies transmission of drug-resistant Salmonella /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487327695620759.
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Jugan, Maria Christine. "Effects of Akkermansia muciniphila Supplementation on Markers of Intestinal Permeability in Dogs Following Antibiotic Treatment." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488318772663017.
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Gregg, Amy B. "The immunological effects of antibiotic treatment and probiotic populations on oral tolerance in ova fed mice." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1371839.
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Probiotics are a live microbial supplement that reside within the intestinal tract and are considered normal flora. The Balb/c mouse model was used to determine if the elimination of probiotics, general LAB species, by antibiotics plays a role in the breakdown of oral tolerance leading to the generation of an immune response to oral antigens. A mouse model was developed for in vivo research regarding probiotic populations and the effect on the induction of oral tolerance. The Balb/c mouse was used to determine if the mouse model had a colonized intestinal tract with probiotics followed by a reduction of probiotics that was done with orally administered antibiotics. After the reduction of probiotics, mice were fed oral antigen, ovalbumin, to determine that an immune response was not shown with oral antigen alone. After the mouse model was set up, mice were then fed oral antigen and then stimulated with immunizations to study the induction of oral tolerance and the possible effect of the absence of probiotics. The results indicated that mice with reduced probiotics and fed with oral antigen alone do not show an immune response. In contrast, mice fed with oral antigen followed by immunization indicate a higher OVA-specific serum IgG. This is evidence that correlates with clinical findings in disease states such as Crohn's Disease and Irritable Bowel Syndrome (IBD).<br>Department of Biology
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Aziz, Seemal. "Antibiotic Susceptibility Testing: Effects Of Variability In Technical Factors On Minimum Inhibitory Concentration Using Broth Microdilution." Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454819.
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Background Broth microdilution (BMD) is a gold-standard reference method to determine minimum inhibitory concentration (MIC) of antibiotics. For this, a standardized concentration of bacterial inoculum (2e5–8e5 colony-forming units, CFU/ml) is added to progressively higher concentrations of antibiotics. Bacteria stop growing at a particular antibiotic concentration termed MIC. Like other assays, various biological and/or technical factors can affect BMD results. Aims To investigate the effects of inoculum concentration (5e4–5e6 CFU/ml), growth-medium concentration (cation-adjusted Mueller-Hinton Broth (CAMHB)), ranging 0.5x to 2x (1x as standard)) and age (<6-months or >1-year old) of fastidious medium on MIC results. And to compare BMD results using 5 different brands of CAMHBs and 1 cation-non-adjusted MH-broth (non-CAMHB). Methods 12 isolates of bacteria (gram-positive (n=3), gram-negative(n=5), fastidious isolates (n=7)) and custom-made antibiotics-containing plates for gram-positive (11 antibiotics) or gram-negative bacteria (10 antibiotics) were used. Overnight-grown colonies were used to prepare BMD solutions (MH-broth + inoculum +/- fastidious) which were plated on antibiotic-plates as well as diluted prior to plating on agar-plates. Antibiotic- and agar-plates were incubated (18–20hr, 35°C) and used to determine MICs (following European Committee on Antimicrobial Susceptibility Testing instructions) and actual number of viable bacteria in BMD solutions, respectively. Results Increasing inoculum concentration increased MICs of all antibiotics except cefoxitin. Piperacillin–tazobactam, levofloxacin, benzylpenicillin and ampicillin were especially sensitive to increase in inoculum and showed a 4-fold increase in >50% isolates. MICs for tobramycin, tigecycline and gentamicin increased by 2-fold in >50% isolates every time MH-broth concentration increased. Age of fastidious medium had no decipherable pattern of effects on MIC. All MH-broths gave similar results except when testing daptomycin which gave higher MICs with non-CAMHB compared to CAMHB. Conclusion This research reveals some technical factors affecting MIC results. These results could help define parameters for automated BMD-performing-systems. However, this research shows only trends as more replicates are needed to determine statistically significant results.
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Hossain, Amzad. "Altering the fetal programming of the HPA axis and the consequences in the adult auditory system /." Stockholm : Karolinska institutet, 2006. http://diss.kib.ki.se/2006/91-7357-040-0/.
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Glew, Lindsey. "The effects of oxygen and reactive oxygen species on antibiotic resistance and microbial communities in chronic wounds." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/2527.
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Infection is one of the factors that may contribute to non-healing of chronic wounds; the presence of antibiotic resistant bacteria serves to exacerbate the problem due to limited treatment options. Bacteria utilise several mechanisms to survive exposure to antibiotics, including synthesis of deactivating enzymes, target modification or substitution, changes to membrane permeability, upregulation of efflux pumps and the formation of a biofilm. Quorum sensing is a density-dependent mechanism of bacterial cell to cell communication that can be instrumental in co-ordinating biofilm initiation. Hyperbaric oxygen therapy (HBOT) is an option offered to some patients with chronic wounds, including diabetic foot ulcers. Evidence suggests that HBOT can reduce the incidence of major amputation in these patients. As well as the direct toxicity of increased tissue oxygenation on anaerobic bacteria HBOT may also increase levels of reactive oxygen and nitrogen species in the wound environment. This study aimed to investigate the effects of hyperoxia and oxidative damage on three specific mechanisms of antibiotic resistance: the activity of penicillinase, an antibiotic deactivating enzyme synthesised by bacteria; the activity of quorum sensing signalling molecules (AHLs); and biofilms and their associated bacteria. It also analysed the population dynamics of, primarily, bacteria in diabetic foot ulcers during HBOT, by the use of molecular analysis tools such as PCRDGGE. The presence of fungal species was investigated in wounds prior to HBOT and in two wounds at two points during HBOT. This study found that hydrogen peroxide, hypochlorous acid and peroxynitrite reduced the activity of penicillinase in vitro. Hypochlorous acid reduced the activity of a range of AHLs in vitro but not in vivo. Oxygen concentration did not have any impact on biofilm mass, nor did it significantly affect the ability of an oxidant-generating enzyme to reduce live bacterial cells within a biofilm. The population dynamics of bacterial species identified in all the wounds were complex and did not undergo identifiable changes during HBOT. Fungal species were identified in all wounds prior to HBOT, though different profiles were observed in the two wounds investigated during HBOT. These results suggest that oxidants could play a role in the attenuation of antibiotic resistance in chronic wound bacteria. It is unclear whether HBOT alters the population dynamics of non-healing wound microflora
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Conlon-Bingham, Geraldine Mary. "A multi-faceted approach to controlling healthcare-acquired infections : the effects of infection control and antibiotic cycling." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705891.
Full textAbstract:
Healthcare-acquired infections are a major cause of morbidity and mortality and are estimated to cost the National Health Service £1 billion per year. In order to reduce the burden of these infections, focus has been placed on infection control and antimicrobial stewardship interventions. The overall aim of the present research was to assess the impact of an infection control and antibiotic stewardship intervention on the incidence of hospital-acquired (HA) methicillin resistant Staphylococcus aureus and HA-Clostridium difficile infection (CDI) in Antrim Hospital. The first study described in Chapter 2 demonstrates how a change in environmental disinfectant from sodium dichloroisocyanurate (NaDCC) to chlorine dioxide (CIO2) resulted in a significant decrease in the incidence of HA-MRSA, despite an increase in the use of high risk antibiotics during the study period. The antibiotic stewardship intervention investigated in this research programme involved the introduction of an antibiotic cycling policy in Antrim Hospital. The development of the policy was based on an investigation of the effects of antibiotic use on the incidence of HA-CDI and HA-MRSA in the study site hospital (Chapter 3). Autoregressive Integrated Moving Average (ARIMA) time series analysis identified antibiotics that were significantly associated with HA-CDI and HA-MRSA. Based on these findings an antibiotic cycling policy was developed, which was implemented in Antrim Hospital for a period of eighteen months (Chapter 4). This policy resulted in no effect on the incidence of HA-CDI, however, a rising HA-MRSA trend was observed. The presented work provides a comprehensive assessment of an infection control intervention and is the first study to date to develop and to evaluate an antibiotic cycling policy based on an analysis of local epidemiology data using ARIMA modelling.
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Pränting, Maria. "Bacterial Resistance to Antimicrobial Peptides : Rates, Mechanisms and Fitness Effects." Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-130168.
Full textAbstract:
The rapid emergence of bacterial resistance to antibiotics has necessitated the development of alternative treatment strategies. Antimicrobial peptides (AMPs) are important immune system components that kill microbes rapidly and have broad activity-spectra, making them promising leads for new pharmaceuticals. Although the need for novel antimicrobials is great, we also need a better understanding of the mechanisms underlying resistance development to enable design of more efficient drugs and reduce the rate of resistance development. The focus of this thesis has been to examine development of bacterial resistance to AMPs and the resulting effects on bacterial physiology. The major model organism used was Salmonella enterica variant Typhimurium LT2. In Paper I, we observed that bacteria resistant to PR-39 appeared at a high rate, and that the underlying sbmA resistance mutations were low cost or even cost-free. Such mutants are more likely to rapidly appear in a population and, most importantly, will not disappear easily once the selective pressure is removed. In paper II, we isolated protamine-resistant hem- and cydC-mutants that had reduced growth rates and were cross-resistant to several other antimicrobials. These mutants were small colony variants (SCVs), a phenotype often associated with persistent infections. One SCV with a hemC-mutation reverted to faster growth when evolved in the absence of protamine. In paper III, the mechanism behind this fitness compensation was determined, and was found to occur through hemC gene amplification and subsequent point mutations. The study provides a novel mechanism for reversion of the SCV-phenotype and further evidence that gene amplification is a common adaptive mechanism in bacteria. In Paper IV, the antibacterial properties of cyclotides, cyclic mini-proteins from plants, were evaluated. Cycloviolacin O2 from violets was found to be bactericidal against Gram-negative bacteria. Cyclotides are very stable molecules and may be potential starting points for development of peptide antibiotics.
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Sloan, David Alexander. "Colon neoplasia in an experimental model : the effects Diet, injury, and antibiotic manipulation of the gut bacterial flora." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65941.
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FILHO, LUIZ DA SILVA GOES. "SOLVENT EFFECTS ON SPECTROSCOPIC PROPERTIES OF THE ANTIBIOTIC NORFLOXACIN: UV-VIS ABSORPTION, STEADY STATE AND TIME-RESOLVED FLUORESCENCE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=17692@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>Norfloxacina (NOR) é um antibiótico e antitumoral sintético da classe das
fluorquinolonas. A carga elétrica de seu íon molecular é determinada
principalmente pelo estado de protonação de dois grupos funcionais: o grupo
carboxílico no anel quinolônico e a amina do grupo piperazinil. O equilíbrio de
espécies com diferentes estados de protonação influencia tanto as propriedades
espectroscópicas quanto a atividade farmacológica da droga. NOR apresenta-se
positivamente carregada em meio ácido, neutra ou zwiteriônica em meio neutro e
negativamente carregada em meio básico. No presente trabalho, investigamos as
propriedades espectroscópicas da norfloxacina, através de absorção ótica e de
fluorescência estacionária e resolvida no tempo, em soluções aquosas de
diferentes pH e em diferentes solventes orgânicos. Parâmetros fotofísicos como
coeficiente de absorção molar, deslocamento de Stokes, rendimento quântico, e
tempo de vida de fluorescência foram obtidos. O deslocamento de Stokes e a
frequência de emissão foram analisados em 16 solventes, agrupados
principalmente em solventes próticos e apróticos, levando em consideração efeitos
gerais, como a polarizabilidade de orientação dos solventes, e efeitos específicos.
Foi observado que, apesar de os espectros de absorção UV-visível não
apresentarem diferenças substanciais na maioria dos solventes, o deslocamento de
Stokes e, especialmente, o rendimento quântico de fluorescência são fortemente
afetados pelo solvente. Foram construídos gráficos de Lippert, do desvio de
Stokes ou da frequência de emissão como função da polarizabilidade de
orientação do solvente. Mesmo introduzindo correção para transferências de carga
fotoinduzidas, segundo a teoria de Weller, não foram obtidas boas correlações.
Por outro lado, para a maioria dos solventes, encontrou-se correlação entre os
desvios de Stokes e os valores do parâmetro ET(30) da escala empírica de
polaridades elaborada por Reichardt e baseada no forte solvatocromismo da
absorção do corante betaína 30. Decaimentos de fluorescência de NOR nos
diferentes solventes foram obtidos por contagem de fótons e foram ajustados com
expressão para distribuição de tempos de vida em torno de um único tempo, ou de
múltiplas exponenciais no caso de mais de um tempo de vida. Foram também
estudadas absorção e fluorescência de NOR em misturas binárias de solventes:
etanol-tampão e DMSO-tampão, com tampões de pH 4.2 e 7.5. As curvas obtidas
para as modificações no rendimento quântico em função da proporção de tampão
na mistura são características de efeitos específicos de solventes e apontam o
equilíbrio de protonação-desprotonação dos grupos amina e carboxílico como
tendo papel fundamental no rendimento quântico e no deslocamento de Stokes. Os
resultados mostraram que, sendo a fluorescência de NOR particularmente sensível
a pequenas quantidades de solventes orgânicos, especialmente em pH fisiológico,
constitui um importante sensor espectroscópico para sondar interações do
antibiótico com moléculas biologicamente relevantes.<br>Norfloxacin (NOR) is a synthetic antibiotic and antitumoral drug of the
class of fluoroquinolones. The electric charge of this molecular ion is mainly
determined by the protonation equilibrium of two functional groups: the carboxyl
of the quinolone heterocycle, and the distal amine of the piperazinyl group. The
equilibrium of species with different charge distributions influences both the
spectroscopic properties and pharmacological activity of the drug: NOR is
positively charged in acidic medium, neutral or zwitterionic in neutral medium,
and negatively charged in basic medium. In the present work, we investigated the
spectroscopic properties of norfloxacin using UV-vis optical absorption, and
steady state and time-resolved fluorescence in different aqueous solutions and
organic solvents. Photophysical parameters such as molar absorption coefficients,
Stokes shifts, quantum yields, and fluorescence lifetimes were obtained. The
Stokes shift and the emission frequency were analyzed in 16 solvents, mainly
grouped as protic and aprotic solvents, taking into account general effects of the
solvents, such as orientation polarizability, and specific effects. It was observed
that, although the UV-vis absorption spectra do not present substantial difference
in most solvents, the Stokes shift and specially the fluorescence quantum yield are
strongly affected by the solvent. Lippert plots of the Stokes shift and the emission
frequency versus solvent orientation polarizability were constructed. Even
introducing a correction for photoinduced charge transfer, according to the
Weller’s theory, a good correlation was not found. On the other hand, a good
correlation was found between the Stokes shift and the parameter ET(30), of the
empirical scale developed by Reichardt and based on the strong solvatochromism
of the betain 30 dye. Fluorescence decays in different solvents were obtained
using time correlated single photon counting (TCSPC) and were fitted with the
expression for lifetime distribution around a single lifetime, or using a
multiexponential expression in the case of more than one lifetime. Optical
absorption and fluorescence of NOR were also studied in binary mixtures of
solvents: ethanol-buffer and DMSO-buffer, with pH 4.2 and 7.5 buffers. The
curves of the fluorescence intensity as a function of the proportion of buffer in the
mixture are characteristic of specific solvent effects, and point out that the
protonation-deprotonation equilibrium of the amine and carboxylic groups plays a
fundamental role in determining the quantum yield and the Stokes shift. The
results showed that the fluorescence of NOR is an important spectroscopic sensor
to explore interactions with biologically relevant molecules, since it is particularly
sensitive to small amounts of organic solvents, especially at physiological pH.
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Vance, Lindsey. "The Inhibitory Effects of a Novel Gel on Staphylococcus aureus Biofilms." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/honors/435.
Full textAbstract:
Antibiotic resistance is an ever-growing topic of concern within the medical field causing researchers to examine the mechanisms of resistance to develop new antimicrobials. Bacteria’s ability to form biofilms is one mechanism which aids in antimicrobial resistance. Staphylococcus aureus is of special interest as it is one of the most frequent biofilm-forming bacteria found on medical devices causing infections and posing dangerous threats in a clinical setting. A recently developed antimicrobial gel has been shown to have profound effects on treating bacterial infections and wound healing. This research is centered upon examining the antimicrobial effects of this gel on the three different stages of biofilm formation in clinical and laboratory strains of S. aureus. Through a series of experiments examining the effects this gel has on S. aureus at the stages of biofilm attachment, maturation, and dispersion, the gel has shown significant levels of inhibition. These findings indicate that the novel gel disrupts biofilm forming processes of S. aureus, which provides useful information for fighting infections in the medical field. Further research on the uses and effects of this new gel could lead possibility using the antimicrobial compound for a variety of clinical purposes.
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Metch, Jacob W. "Effects of Microbial Community Stress Response and Emerging Contaminants on Wastewater Treatment Plants." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85257.
Full textAbstract:
As the population in water stressed areas increases, it is critical that wastewater treatment plants (WWTPs) continue to replenish depleted water supplies, and serve as an alternative water source. WWTPs depend on microorganisms in activated sludge to remove pollutants from wastewater and therefore an understanding of how these microorganisms are affected by various conditions and pollutants is needed. Also, as consumer products and industrial processes evolve, so do the pollutants they discharge to wastewater. In order to keep pace with these changes, understanding the effects of emerging contaminants to WWTP processes is essential. The research herein assesses microbial community dynamics of the response of nitrifying microorganisms in activated sludge to variation in ammonia concentration and evaluates the impact of engineered nanoparticles on activated sludge microbial communities and other emerging pollutants, such as antibiotic resistance genes and disinfection by-products.
In order to assess microbial community dynamics of the response of nitrifying microorganisms to removal of ammonia in the feed, nitrifying activated sludge reactors were operated at various relevant temperatures and the nitrifying microbial community was characterized using activity assays and bio-molecular techniques. We found that Nitrospira spp. were the dominant nitrifying microorganisms, exhibiting stable relative abundance across multiple trials and over a range of temperatures. These results indicate the possibility of comammox bacteria in the system and highlight the complexity of nitrifying microbial communities in activated sludge relative to past understanding.
Both microbial and chemical impacts of engineered nanoparticles on WWTP processes were also investigated. Metagenomic analysis of DNA extracted from activated sludge sequencing batch reactors dosed with gold nanoparticles with varied surface coating and morphology indicated that nanoparticle morphology impacted the microbial community and antibiotic resistance gene content more than surface coating. However, nanoparticle fate was controlled by surface coating more than morphology. Disinfection by-product formation in the presence of nanoparticles during WWTP disinfection was assessed using silver, titanium dioxide, ceria, and zero valent iron nanoparticles. Silver nanoparticles were found to enhance trihalomethane formation, which was attributed to the citrate coating of the nanoparticles. These studies both raise concern over the relationship between engineered nanoparticles and other emerging concerns in WWTPs, and take a step towards informing nanoparticle design in a manner that limits their associated environmental impact.<br>Ph. D.
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Valério, Nádia Castanho. "Potential effects between bacteriophages and antibiotics to inactivate Escherichia coli." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/22360.
Full textAbstract:
Mestrado em Microbiologia<br>Escherichia coli is part of the normal flora of the gastrointestinal tract of humans and various mammals. This opportunistic microorganism is capable of cause several infections, such as urinary tract infections (UTI). E. coli is resistant to a large number of antibiotics, becoming harder the control of infections caused by this bacterium. Phage therapy may be a useful tool to control infections caused by antibiotic resistant strains. However, the major concern of the phage therapy is also the emergence of phage resistant bacteria. In this study, was evaluated the combination of two different therapies, chemotherapy and phage therapy, to evaluate the possibility of synergic effects between them. It was used the phage ECA2 (a phage previously isolated by the research group) and various antibiotics (ampicillin, kanamycin, piperacillin, tetracycline, chloramphenicol and ciprofloxacin) with different mechanisms of action. The E. coli strain used in this study is sensitive to the antibiotics ciprofloxacin, tetracycline and chloramphenicol and resistant to the antibiotics ampicillin, kanamycin and piperacillin The phage ECA2 caused a reduction in E. coli concentration of ≈ 4.5 log after 2 hours of treatment in phosphate buffered saline (PBS). The results obtained with the mixtures of the phage with ampicillin, kanamycin and piperacillin did not cause significantly differences when compared with the results obtained just with the phage. As the bacterium E. coli showed resistance to those antibiotics, the bacterial inactivation was just due the action of the phage. Otherwise, the results obtained using the mixtures of ECA2 with tetracycline and chloramphenicol were worse than the results obtained just with the phage. The conjugation of the phage with ciprofloxacin resulted in a bacterial inactivation of about 8.3 log, compared to the ≈4.5 log of bacterial inactivation obtained with the phage alone. In addition, the conjugation of the phage ECA2 with ciprofloxacin resulted in a decrease of the bacterial resistances obtained the phage and the antibiotic individually. The efficacy of phage therapy in urine was also evaluated, with the phage and the mix of phage and ciprofloxacin. The inactivation of E. coli in urine samples was similar to that obtained in PBS. It was observed a decrease of 4.3 log after 4 hours of treatment. Furthermore, a cocktail with two phages, the phage ECA2 and another E. coli specific phage, previously isolated by the research group, the phage phT4A, was also tested. The E. coli inactivation was 3.5 log after 4 hours. The results indicate that phage and antibiotic combinations could result in synergistic effect in the inactivation of bacteria, but only when the bacterium is sensitive to the antibiotic. Also, the combination of antibiotics with phages contributes to managing resistance levels, controlling the antibiotic resistance and phage-resistant mutants. The phages limit the emergence of antibiotic resistant variants in combined treatments independently of antibiotic type, but the antibiotics limit the resistance of phage-mutants only when bacteria are sensitive to the antibiotic. However, overall, in the presence of antibiotics the resistance of phage-mutants was the same or less than when phages were tested alone. The high bacterial inactivation efficiency with phages combined with a higher bacterial inactivation in the presence of antibiotic and the long periods of phage survival in urine samples, paves the way for depth studies to control urinary tract infection and to overcome the development of resistances by E. coli, the bacterium most frequently isolated in UTI at the community level and at hospital settings<br>Escherichia coli é uma bactéria oportunista que pode ser encontrada como parte da flora normal do trato gastrointestinal humano e de alguns mamíferos. Este microrganismo é capaz de provocar diversas infeções, sendo responsável pela maioria das infeções do trato urinário (ITU). E. coli é resistente a uma grande variedade de antibióticos, tornando difícil o tratamento de infeções por ela causadas. Deste modo, a terapia fágica pode ser uma ferramenta útil no tratamento de infeções causadas por estirpes de E. coli resistentes aos antibióticos. Contudo, também a terapia fágica também leva ao desenvolvimento de bactérias mutantes resistentes aos fagos. Por esta razão, neste trabalho, foi avaliada a combinação de duas terapias, quimioterapia e terapia fágica, de modo a avaliar possíveis efeitos sinérgicos e atenuar o desenvolvimento de resistências aos fagos e antibióticos. Foi usado o fago ECA2, isolado num estudo prévio, e vários antibioticos (ampicilina, canamicina, piperacilina, ciprofloxacina tetraciclina e cloranfenicol) com diferentes mecanismos de ação. A estirpe de E. coli usada é sensível aos antibióticos ciprofloxacina, tetraciclina e cloranfenicol e resistente aos antibióticos ampicilina, canamicina e piperacilina. O fago ECA2 inativou eficientemente a bactéria E. coli, causando uma redução de ≈4,5 log na concentração da bactéria após 2 horas de tratamento em phosphate buffered saline (PBS). A inativação bacteriana com a mistura de fago e antibióticos ampicilina, canamicina e piperacilina foram similares aos resultados obtidos apenas com o fago. Como a estirpe bacteriana apresentava resistência a estes antibióticos, a inativação bacteriana resultante foi devida apenas à ação do fago. As misturas do fago ECA2 com cloranfenicol e com tetraciclina mostraram ser menos eficazes na inativação da bactéria do que o fago sozinho. A conjugação do fago com a ciprofloxacina resultou numa inativação bacteriana de cerca de 8,3 log, em detrimento dos ≈ 4,5 log de inativação bacteriana obtidos com apenas o fago. Além disso, a conjugação do fago ECA2 com a ciprofloxacina resultam numa diminuição das resistências bacterianas obtidas em relação ao fago e ao antibiótico individualmente. A terapia fágica também foi avaliada em urina com vista a avaliar o uso desta terapia no controlo de infeções urinárias. A inativação de E. coli na urina foi semelhante à obtida nos ensaios em PBS, tanto para o fago como para a conjugação do fago ECA2 com a ciprofloxacina. Foi ainda testado na urina um cocktail com dois fagos, o fago ECA2 e com outro fago específico para esta bactéria, o fagophT4A (previamente isolado pelo grupo de trabalho). Observou-se numa redução bacteriana de 3,5 log. Os resultados indicam que a combinação fagos e antibióticos pode resultar num efeito sinérgico na inativação de bactérias, mas apenas quando a bactéria é sensível ao antibiótico. Além disso, a combinação de antibióticos com fagos contribui para a gestão dos níveis de resistência, controlando a resistência aos antibióticos e os mutantes resistentes ao fago. Os fagos limitam o desenvolvimento de variantes resistentes a antibióticos em tratamentos combinados independentemente do tipo de antibiótico, mas os antibióticos limitam a resistência de mutantes aos fagos apenas quando as bactérias são sensíveis ao antibiótico. Contudo, em geral, na presença de antibióticos, a resistência dos mutantes aos fagos foi a mesma ou menor do que quando os fagos foram testados isoladamente. A elevada eficiência de inativação bacteriana por fagos combinada com uma maior inativação bacteriana na presença de antibiótico, e a elevada sobrevivência dos fagos em urina, abre o caminho para estudos mais aprofundados para controlar a UTI e o desenvolvimento de resistências em E. coli, a bactéria mais frequentemente isolada em UTI ao nível da comunidade e em ambientes hospitalares.
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Khan, Ghazanfar Ali. "Monitoring anti-infectives and antibiotic resistance genes : with focus on analytical method development, effects of antibiotics and national perspectives." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-61682.
Full textAbstract:
Antibiotics are biologically active and are globally used in humans and animal medicine for treatment and in sub-therapeutic amounts as growth promoters in animal husbandry, aquaculture and agriculture. After excretion, inappropriate disposal and discharge from drug production facilities they enter into water bodies either as intact drugs, metabolites or transformed products. In water environments they promote development of antibiotic resistance genes (ARGs) which could serve as a reservoir and be horizontally transferred to human-associated bacteria and thus contribute to AR proliferation. Measurement of antibiotics has been revolutionized with the usage of solid phase extraction (SPE) for enrichment followed by Liquid chromatography mass spectrometry (LC-MS). On-line SPE coupled to LC-MS/MS has the advantages of high sample throughput, low sample preparation time and minimal solvent utilization. Constructed wetlands (CWs) are potential alternatives to conventional treatment plants to remove organic pollutants. A study at Plönninge, Halmstad was performed to assess the impact of bacterial community pattern and development of resistance in spiked (n=4) and control (n=4). CWs were spiked with antibiotics at environmentally relevant concentrations continuously for 25 days. Shannon Index (H’) were used to determine the bacterial diversity and real-time PCR detected and quantified antibiotic resistance genes (ARGs) sulI, tetA, tetB, erm, dfrA1, qnrS and vanB and class 1 integrons intI1. No significant differences in bacterial compositions or in ARGs or integron concentrations could be discerned between exposed and control wetlands. A study conducted in Northern Pakistan showed that the antibiotic levels in most studied rivers were comparable to surface water measurements in unpolluted sites in Europe and the US. However, high levels of antibiotics were detected in the river in close vicinity of the 10 million city Lahore, e.g. 4600 ng L−1 sulfamethoxazole. Highest detected levels were at one of the drug formulation facilities, with measured levels up to 49000 ng L−1 of sulfamethoxazole for example. The highest levels of ARGs detected, sul1 and dfrA1, were directly associated with the antibiotics detected at the highest concentrations, sulfamethoxazole and trimethoprim. In the study in UK, sewage epidemiology surveillance is used to measure the oseltamivir carboxylate (OC), metabolite of oseltamivir (parent drug) in twenty four time proportional hourly influent samples from two WWTPs and then back-calculations were made to assess the compliance of drug. Predicted users of oseltamivir, based on measured OC in waste water, ranged from 3-4 and 120-154 people for the two WWTP catchments, respectively, which are consistent with the projected use from national antiviral allocation statistics, 3-8 and 108-270, respectively. Scenario analysis suggests compliance was likely between 45-60% in the study regions.
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Tello, Gildemeister Alfredo. "A study into the effects and environmental risk of antibiotics used in freshwater aquaculture on environmental bacteria." Thesis, University of Stirling, 2012. http://hdl.handle.net/1893/9930.
Full textAbstract:
Aquaculture is the fastest growing food industry in the world and it accounts for roughly half of the world's fish supply. The majority of global aquaculture production occurs in freshwater systems that are increasingly subject to multiple uses by different stakeholders. Given the overall scarcity of freshwater on a global scale, freshwater aquaculture will face increasing environmental constraints that will demand an ever better understanding of its potential impacts on the aquatic environment and human health. This thesis consists of a series of studies that, collectively, contribute to further our understanding on the effects of freshwater aquaculture effluents on aquatic ecosystems, on the effects and environmental safety of antibiotics used in freshwater aquaculture on aquatic bacterial communities and on the link between antibiotic pollution and antibiotic resistance. Chapter 2 reviews the effects of freshwater aquaculture effluents on stream ecosystems using land-based salmonid farms as a case study. In this chapter I discuss relevant considerations related to the temporal and spatial scales of effluent discharge and ecological effects that highlight the need to characterize the patterns of stressor discharge when assessing environmental impacts and designing ecological effects studies. I also discuss the potential role of multiple stressors - with an emphasis on veterinary medicines - in disrupting ecosystem structure and function. Overall, the critical analysis presented in this chapter indicates that further research on the effects of veterinary medicines using relevant exposure scenarios would significantly contribute to our understanding of their impact in relation to other effluent stressors. Chapter 3 is a general methods chapter that describes the stream microcosm system used to assess the effects of erythromycin thiocyanate (ERT) and florfenicol (FFC) on bacterial communities of stream biofilms. This chapter presents the results of preliminary experiments whose results provided relevant information on the overall operation of the microcosms and on the variability of major physical and biological variables. This information guided the experimental designs used to assess the effects of FFC and ERT on the bacterial community structure of stream biofilms. Chapter 4 presents the results of the experiment conducted to assess the effects of FFC on the bacterial community structure of developing biofilms. The objective was to assess changes in bacterial community structure along a gradient of FFC concentrations that could provide insight into the type and magnitude of effects that could be expected from episodic exposure of stream biofilms to FFC in headwater streams. At 10 and 20 days of biofilm development, bacterial community structure differentiated in a pattern consistent with the FFC concentration gradient and there was a positive relationship between bacterial richness and bacterial diversity with FFC concentration. At 15 days of biofilm development there was also a positive relationship between FFC concentration and the surface coverage of bacteria and extracellular polymeric substances. These trends declined as the biofilm developed a more complex architecture, in terms of thickness and in the surface coverage of algae. The results are consistent with an initial stimulatory effect of FFC on biofilm formation that triggered changes in bacterial community structure that were gradually compressed as the development of a complex biofilm architecture increased the relative importance of autogenic ecological processes. The results suggest that the co-occurrence of FFC with bacterial pathogens in effluents and wastewaters may favour their persistence in the environment by enhancing biofilm formation. Chapter 5 presents the results of the experiment conducted to assess the effects of ERT on the bacterial community structure of developing biofilms. Currently, Aquamycin® 100 - a Type A medicated article (i.e., Premix) containing 100 g ERT lb-1 and used to produce a Type C medicated feed - is a candidate drug for approval by the US FDA to control mortality associated with bacterial kidney disease in freshwater salmonids. The objective of this experiment was to assess the effects of ERT on the bacterial community structure of stream biofilms using an exposure period consistent with the 28-day treatment regime suggested for Aquamycin® 100. The results provide no evidence to suggest that a 30-day exposure to ERT concentrations in the range of 10 μg L-1 (i.e., 7.3 ± 3.9 μg L-1) would lead to changes in the bacterial community structure or overall bacterial abundance of stream biofilms, while they suggest that these effects may occur at concentrations in the range of 100 μg L-1 (i.e., 87.2 ± 31.1 μg L-1). Chapter 6 attempts to determine whether environmental concentrations of antibiotics and concentrations representing action limits used in environmental risk assessment may exert a selective pressure on clinically relevant bacteria in the environment. In this chapter I use bacterial inhibition as an assessment endpoint to link antibiotic selective pressures to the prevalence of resistance in bacterial populations. Species sensitivity distributions were derived for three antibiotics by fitting log-logistic models to endpoints calculated from minimum inhibitory concentration (MIC) distributions based on worldwide data collated by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Bacteria represented in these distributions were placed in a broader context by performing a brief phylogenetic analysis. The potentially affected fraction of bacterial genera at measured environmental concentrations of antibiotics and environmental risk assessment action limits was used as a proxy for antibiotic selective pressure. Measured environmental concentrations and environmental risk assessment action limits were also directly compared to wild-type cut-off values. Results suggest that measured environmental concentrations of antibiotics and concentrations representing environmental risk assessment action limits are high enough to exert a selective pressure on clinically relevant bacteria that may lead to an increase in the prevalence of resistance. Chapter 7 presents the results of an exploratory analysis conducted to assess the abundance of class 1 integrons in stream biofilms exposed to FFC and ERT. There was no pattern in the abundance of intI1 genes consistent with the treatment of FFC and ERT, suggesting either the absence of gene cassettes involved in dealing with selective pressures caused by these antibiotics or that the concentrations tested were below those required to give them a selective advantage. Chapter 8 is a brief general discussion that brings together the findings of the thesis and makes suggestions for future research. Key areas identified for future research include assessing in further detail the stimulatory effect of FFC on biofilm formation in complex bacterial communities, the interactive effects of multiple aquaculture effluent stressors on aquatic bacterial communities and their potential effects on the development of antibiotic resistance, the fate of FFC and ERT in stream ecosystems, and further developing the analysis based on MIC distributions presented in chapter 6 to assess the potential effects of antibiotic pollution on the selection of multi-drug resistance in the environment.
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Worlock, Peter Harrison. "The prevention of infection in open fractures : an experimental study of the effects of fracture stability and of antibiotic therapy." Thesis, University of Nottingham, 1986. http://eprints.nottingham.ac.uk/13676/.
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An experimental model of a contaminated open fracture has been developed in rabbits, using a reproducible midshaft fracture of the tibia. This model has been used to: 1) Test the hypothesis that stable fixation of an open fracture will reduce its susceptibility to infection. 2) Assess the effect of antibiotics on infection rate, with particular reference to the delay in administering the initial dose. The pattern of fracture healing was initially determined for stable and unstable fixation, without inoculation with bacteria. Fractures fixed with a dynamic compression plate ("stable" group) healed by primary bone union, while fractures stabilised with a loose-fitting intramedullary rod ("unstable" group) healed by external callus formation. Forty- one rabbits were used in the definitive study of the effect of stability. All fractures were inoculated with Staphylococcus aureus in a standard concentration. There were twenty rabbits in the stable group (compression plate) and osteomyelitis developed in seven (35%). Of the twenty- one rabbits in the unstable group (loose- fitting intramedullary rod), fifteen (71%) became infected. This difference in infection rate is statistically significant (p<0.02). The "rod- fixed fracture" model had the highest infection rate and was therefore used to study the effect of antibiotics. Fifty-one rabbits were used; a single intramuscular injection of cephradine was given to each animal at varying times in relation to inoculation with bacteria. Although the maximal reduction in infection rate was observed when the antibiotic was given before inoculation with bacteria, a 40% decrease in the infection rate was still seen when the antibiotic was given after bacterial inoculation. This effect persisted even if the initial dose of antibiotic was delayed four hours after inoculation. These findings support the concept of stabilisation of open fractures in man; and suggest that appropriate systemic antibiotics should be routinely used in the management of open fractures in man, even if the treatment is delayed up to four hours after injury.
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Everett, Lucy Margaret. "The effects of antibiotic stress on the expression of virulence factors by strains of Staphylococcus aureus diplaying vancomycin-intermediate resistance." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272854.
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Knecht, Henrik [Verfasser]. "Perturbation of the human gut microbiota due to antibiotic treatment and potential effects predisposing to infection with Clostridium difficile / Henrik Knecht." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1044891823/34.
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Marjoshi, Delphine. "Investigating the effects of three herbicides - Kamba, 2,4-D and Roundup on Salmonella enteric serovar Typhimurium growth and antibiotic tolerance phenotypes." Thesis, University of Canterbury. School of Biological Sciences, 2014. http://hdl.handle.net/10092/10284.
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Herbicides are a common tool in weed control. With the introduction of genetically modified herbicide-tolerant crops, there has been a dramatic increase in the use of particular herbicides. Herbicides contaminate the environment and food and feed and can come into contact with non-target organisms, especially bacteria. Salmonella enteric serovar Typhimurium, which is a human and animal pathogen, was chosen to investigate if the commercial formulations of three herbicides – Kamba, 2,4-D and Roundup are toxic to bacteria and whether sub-lethal concentrations cause a response to antibiotics. In addition, earlier work demonstrating an effect of salicylic acid on antibiotic response was reconfirmed in this study.
The herbicides were toxic to S. typhimurium at concentrations above the manufacturers recommended application rates. A key finding of this study was that when S. typhimurium was grown in sub-lethal concentrations of the herbicides, it demonstrated a change in its susceptibility to various antibiotics. Kamba and 2,4-D caused increased tolerance of chloramphenicol, tetracycline, ampicillin and ciprofloxacin and increased sensitivity to kanamycin. Exposure to Roundup caused increased sensitivity to chloramphenicol and tetracycline and increased tolerance towards kanamycin and ciprofloxacin. Roundup had no measureable affect on ampicillin susceptibility.
The minimum concentrations of herbicides that induced an antibiotic response were within the recommended application rates. Furthermore, the minimum 2,4-D concentration that induced tetracycline, chloramphenicol and ampicillin tolerance was at or below the maximum residue limits set for food and feed commodities. Simultaneous exposure to an herbicide and an antibiotic was necessary for the induction of antibiotic tolerance. In addition, the effect of the herbicide on the antibiotic response was faster than the lethal effect of the antibiotics. Kamba induced chloramphenicol, tetracycline, ampicillin and ciprofloxacin tolerance was maintained in the absence of Kamba once tolerance was induced by simultaneous exposure to Kamba and antibiotic.
The emergence of antibiotic tolerance is an important health issue that may compromise treatment of serious bacterial infections. The widespread use of herbicides in agricultural, urban and domestic settings increases the number of bacteria that are exposed to herbicides. The tolerance induced by the herbicides may increase the frequency of antibiotic tolerant strains, increase the chance of co-exposure to antibiotics, and increase the potential for failure to treat bacterial infections as a result.
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Amachawadi, Raghavendra G. "Effects of feeding elevated concentration of copper on prevalence and selection of fecal enterococci positive for transferable copper resistance gene in piglets." Thesis, Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/4097.
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Wei, Xi. "Effects of residual veterinary antibiotics on soil enzyme activity and plant growth." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/830.
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Stiles, Spencer R. "The effects on the antimicrobial properties of Hoshino's triple antibiotic paste when chlorhexidine gluconate (0.12%) is substituted for the propylene glycol and macrogol ointment mixture." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11207.
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Thesis (M.S.)--West Virginia University, 2010.<br>Title from document title page. Document formatted into pages; contains v, 47 p. : col. ill. Includes abstract. Includes bibliographical references (p. 44-47).
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Blauth, Kimberly E. Sobsey Mark D. "Occurrence and potential health effects of antibiotic resistant and pathogenic enteric bacteria on swine animal agriculture and row crop farms in farmers and their neighbors." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1354.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Environmental Sciences, School of Public Health." Discipline: Environmental Sciences and Engineering; Department/School: Public Health.
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Harshman, D. K., B. M. Rao, J. E. McLain, G. S. Watts, and J. Y. Yoon. "Innovative qPCR using interfacial effects to enable low threshold cycle detection and inhibition relief." AAAS, 2015. http://hdl.handle.net/10150/621255.
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UA Open Access Publishing Fund<br>Molecular diagnostics offers quick access to information but fails to operate at a speed required for clinical decision-making. Our novel methodology, droplet-on-thermocouple silhouette real-time polymerase chain reaction (DOTS qPCR), uses interfacial effects for droplet actuation, inhibition relief, and amplification sensing. DOTS qPCR has sample-to-answer times as short as 3 min 30 s. In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, subpicogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. Langmuir and Gibbs adsorption isotherms are used to describe the decreasing interfacial tension upon amplification. Moreover, a log-linear relationship with low threshold cycles is presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection, we anticipate extending this technology to biological research applications such as single cell, single nucleus, and single DNA molecule analyses. Our work is the first demonstrated use of interfacial effects for sensing reaction progress, and it will enable point-of-care molecular diagnosis of infections.
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Schmidtner, Anna-Kristina [Verfasser], and Inga D. [Akademischer Betreuer] Neumann. "New views on an old antibiotic: Effects of minocycline on innate versus stress-induced behavioural, immunological, and microbiome changes / Anna-Kristina Schmidtner ; Betreuer: Inga D. Neumann." Regensburg : Universitätsbibliothek Regensburg, 2019. http://d-nb.info/1188026755/34.
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Schmidtner, Anna-Kristina Verfasser], and Inga D. [Akademischer Betreuer] [Neumann. "New views on an old antibiotic: Effects of minocycline on innate versus stress-induced behavioural, immunological, and microbiome changes / Anna-Kristina Schmidtner ; Betreuer: Inga D. Neumann." Regensburg : Universitätsbibliothek Regensburg, 2019. http://d-nb.info/1188026755/34.
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Hutson, Savannah. "The Effects of Farnesol, a Quorum Sensing Molecule from Candida albicans, on Alcaligenes faecalis." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/539.
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Quorum sensing molecules have become a recent focus of study to learn if and how they can be used, both on their own and in conjecture with current antimicrobial methods, as a means of bacterial control. One such quorum sensing molecule is the sesquiterpene alcohol, Farnesol, which is synthesized and released by the fungus, Candida albicans. In most in-vivo cases, our laboratory has shown that Alcaligenes faecalis overtakes C. albicans, preventing its growth. However, as a way to counteract this inhibitory effect, Farnesol may be one way that Candida has found to fight back. In this study, we focused on the inhibitory properties of Farnesol for growth and motility of A. faecalis, as well as, the molecule’s ability to prevent Alcaligenes from creating biofilms and/or degrading them once they have already been established. Our experiments show evidence that Farnesol is able to inhibit both the growth and motility of A. faecalis, and determination of the specific concentrations of Farnesol needed to see the largest effects on A. faecalis biofilms. Our hope is that in future studies, we will be able to add varying concentrations of the Farnesol to known and widely used antibiotics in order to increase the effectiveness of antibiotics against bacterial strains, both in the Alcaligenes genus and in other genus, that have previously been considered “antibiotic resistant”.
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Roberto, Alescia. "METAL EFFECTS ON FRESHWATER MICROBIAL COMMUNITY COMPOSITION, STRUCTURE, AND FUNCTION IN AN URBAN STREAM." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1543839535987157.
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Settle, Tabatha L. "The effects of a phytogenic feed additive versus an antibiotic feed additive on oxidative stress in broiler chicks and a possible mechanism determined by electron spin resonance and the effect of allopurinol, uric acid sodium salt administration, and inosine on xanthine oxidoreductase activity and plasma uric acid in broilers." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10956.
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Thesis (M.S.)--West Virginia University, 2010.<br>Title from document title page. Document formatted into pages; contains v, 88 p. : ill. (some col.). Includes abstract. Includes bibliographical references.