Dissertations / Theses on the topic 'Environmental pathogens'
To see the other types of publications on this topic, follow the link: Environmental pathogens.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Environmental pathogens.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Karim, Mohammad Rezaul. "Survival of indicator microorganisms and enteric pathogens in wetlands." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284066.
Full textAbstract:
Wetlands containing aquatic plants have been found to economically provide a mechanism for improving the microbial and other quality of wastewater. The purpose of this study was to elucidate the effect of vegetation and sedimentation on the survival of enteric microorganisms in constructed wetlands. The first part of this study was designed to determine the effect of vegetation on the survival of Escherichia coli, Salmonella typhimurium , bacteriophage MS-2 and poliovirus in wetlands. The organisms were added to the water from six wetland systems, containing different aquatic plants. The wetland systems received either fresh water or secondary sewage. The presence of aquatic plants significantly increased the die-off of E. coli, S. typhimurium, bacteriophage MS-2, and poliovirus in fresh water and secondary sewage. Additional work on the survival of E. coli in non-sterile, filter sterilized, and autoclaved wetland water indicated that one of the plausible mechanisms of bacterial die-off in constructed wetlands is through increased microbial competition or predation. The next phase of this study investigated the survival of indicator microorganisms in wetlands similar to field conditions. E. coli, bacteriophage MS-2, and PRD-1 were added to tanks which were unvegetated or contained different aquatic plants. E. coli die-off in unvegetated tanks was greater than the vegetated tanks. Temperature was found to be significantly correlated with the die-off of E. coli. Inactivation of bacteriophage MS-2 in unvegetated tanks was also higher than the vegetated tanks. In contrast, PRD-1 inactivation was greater in the vegetated tanks compared to the unvegetated tanks. Thus, a combination of unvegetated and vegetated wetland would probably result in the greatest reduction of microorganisms by the wetlands. The last phase of this study was to examine the relative occurrence and survival of indicator microorganisms and pathogens in the water column and sediments of two constructed surface flow wetlands. On a volume/wet weight basis the concentration of fecal coliforms and coliphage in the water column and sediment was similar. Giardia and Cryptosporidium concentration in the sediment were one to three logs higher in the sediment compared to the water column. The die-off rates of all the organisms were greater in the water, except for Giardia muris. Giardia die-off in the sediment was greater than in the water column. These results suggest that sedimentation may be the primary removal mechanism for the larger organisms in surface flow wetlands. Overall, these studies suggest that vegetation, microbial competition or predation, temperature/sunlight, and sedimentation play important roles in microbial reduction in constructed wetlands. The effect of vegetation on microbial survival appeared to be indirect, through increasing microbial competition. However, vegetation in constructed wetlands may offset the effect of temperature and sunlight, resulting in a longer survival of microorganisms. Thus a combination of non-vegetated and vegetated wetland would probably result in the greatest reduction of microorganisms from wetlands. Future experiments are needed to examine such combined wetlands.
2
Davis, Elizabeth A. "Diverse environmental Pseudomonas encode unique secondary metabolites that inhibit human pathogens." Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1498481537530199.
Full text
3
Sanchez, Luis R. "Removal of bacterial indicators and pathogens from dairy wastewater by a treatment system." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284075.
Full textAbstract:
An integrated wastewater treatment facility at a dairy in Glendale, Arizona, consisting of an upper subsystem (solids separators, anaerobic lagoons, and aerobic ponds) and lower subsystem (wetland subsystems) has been proven to be successful in reducing indicator organisms and potential pathogens (bacteria, enteric viruses, and parasites). The collection sump of the new integrated system collects all dairy wastewater and pumps it to solid separators, which then flows by gravity to anaerobic lagoons and aerobic ponds. The upper subsystem achieved significant microbial reductions of >98 percent for total coliform, >91 percent for coliphage, >95 percent for enterococci, >91 percent for Listeria monocytogenes, and >99.9 percent for Cryptosporidium . Additional reductions although limited were observed in the outflow from the wetland cells.
4
Barribeau, Seth. "Environmental, social, and genetic factors predisposing Xenopus laevis tadpoles to infection." Thesis, University of Canterbury. Biological Sciences, 2007. http://hdl.handle.net/10092/1868.
Full textAbstract:
This work examines the ecological, social and genetic factors that predispose amphibians to infection. In the last 30 years many amphibian populations have declined due to infectious disease, although few researchers have studied the factors involved in mediating amphibian infection. My research is designed to explore some of these factors. I first examined the effects of crowding, kin composition (the relatedness of individuals in a group), and habitat complexity on the growth and survival of Xenopus laevis tadpoles exposed to the bacterial pathogen Aeromonas hydrophila. In tadpoles, stress, and in particular corticosterone, a hormone associated with stress, is known to inhibit growth. Crowding, kin composition, and habitat complexity have all been linked to tadpole growth. As corticosterone exposure is also linked to reduced immune function, I examined how these ecological factors influence tadpoles' disease resistance. Tadpoles exposed to the bacterium were significantly smaller and more likely to die than control tadpoles. Tadpoles reared only with siblings (pure sibship groups) were larger, less variable in size, and had lower mortality rates than tadpoles reared in mixed sibship groups. The size difference between pure and mixed sibship groups was greatest when they were exposed to the pathogen. Habitat complexity reduced size variation within tanks but did not affect mean tadpole size. Mixed kinship composition and high tadpole density can increase competition, reduce growth, and increase disease susceptibility. These results indicate that growth was inhibited by pathogen exposure but kin association may ameliorate this effect. The Major Histocompatibility Complex (MHC) is an integral part of the vertebrate adaptive immune system. To determine the importance of the MHC in conferring disease resistance in amphibians, I challenged X. laevis tadpoles, bearing different combinations of four MHC haplotypes (f, g, j, and r), with A. hydrophila in two experiments. Exposure to A. hydrophila affected the growth and survival of these tadpoles and that the MHC moderated these effects. Tadpoles with two MHC haplotypes (r and g) were susceptible to this pathogen and tadpoles with the other two haplotypes (f and j) were resistant. Heterozygous tadpoles with both susceptible and resistant haplotypes were always intermediate to either homozygotes in size and survival. These results demonstrate that MHC genotype plays a major role in determining the impact of bacterial pathogens on the growth and survival of X. laevis tadpoles. To test whether the effect of exposure to pathogens differs according to the similarity of the hosts I challenged tadpoles with natural levels of the microorganisms associated with different MHC genotypes by exposing the tadpoles to water preconditioned by adults of different MHC genotypes. If the pathogens are adapted to the MHC genotype of their hosts, tadpoles exposed to water from adults with which they shared MHC haplotypes would be more susceptible than those exposed to water from MHC-dissimilar adults. Alternatively, if the hosts are adapted to their pathogens tadpoles may be more resistant to pathogens from MHC-similar frogs than those from MHC-dissimilar frogs. I found that tadpoles exposed to water from MHC-dissimilar animals developed faster, but without increased growth, and were more likely to die than those exposed to water from MHC-similar animals. Furthermore, there was an optimal difference between the tadpoles’ and the donors’ MHC where tadpoles were sufficiently different to the donor to defend against its locally adapted pathogens, and sufficiently similar to not be exposed to especially virulent foreign pathogens. Finally, I present an inventory of bacteria found in the gut and skin (nonsystemic sites) and heart, muscle, and abdominal cavity (systemic sites) of captive frogs. I found several species of bacteria previously identified as amphibian pathogens and many bacteria in systemic sites that have not been considered pathogenic to amphibians. None of the frogs tested positive for the amphibian chytrid fungus, Batrachochytrium dendrobatidis. I discuss the potential importance of these species of bacteria as amphibian pathogens and as protective probiotics, using New Zealand frogs as a case study. In its sum, this work describes some of the factors that can affect amphibians’ ability to resist disease. I show that the genetic constitution of an individual, specifically in terms of the MHC, affects the impact of a disease, and so too does its social and ecological conditions, including the level of crowding, the kinship of its groupmates and the specific microbial challenges of its immediate environment. I also show that many of the factors linked to tadpole growth and development that are well described in other amphibians also affect Xenopus tadpoles.
5
Mathisen, Peter. "Environmental factors selecting for predation resistant and potentially pathogenic bacteria in aquatic environments." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-133338.
Full textAbstract:
The long history of co-existence of bacteria and their protozoan predators in aquatic environments has led to evolution of protozoa resistant bacteria (PRB). Many of these bacteria are also pathogenic to humans. However, the ecological drivers determining the occurrence of different types of PRB in aquatic environments, and the eco-evolutionary link between bacterial adaptation and the resulting implications for mammalian hosts are poorly known. This thesis examines the impact of nutrients and predation on PRB, as well as the ecological and evolutionary connection between their life in aquatic environments and mammalian hosts. In the first study seven bacterial isolates from the Baltic Sea were investigated for their plasticity of adaptation to predation. The response to predation showed large variation where some bacteria rapidly developed a degree of grazing resistance when exposed to predators. The rapid adaptation observed may result in bacterial communities being resilient or resistant to predation, and thus rapid adaptation may be a structuring force in the food web. With the aim to elucidate the link between occurrence of PRB and environmental conditions, a field study and a laboratory experiment were performed. In both studies three PRB genera were found: Mycobacterium, Pseudomonas and Rickettsia. PRB were found both in oligotrophic and eutrophic waters, indicating that waters of all nutrient states can harbor pathogenic bacteria. However, the ecological strategy of the PRB varied depending on environmental nutrient level and disturbance. Using an advanced bioinformatic analysis, it was shown that ecotypes within the same PRB genus can be linked to specific environmental conditions or the presence of specific protozoa, cyanobacteria or phytoplankton taxa. These environmental conditions or specific plankton taxa could potentially act as indicators for occurrence of PRB. Finally, using four mutants (with specific protein deletions) of the pathogenic and predation resistant Francisella tularensis ssp. holarctica, I found evidence of an eco-evolutionary connection between the bacterium´s life in aquatic and mammalian hosts (aquatic amoeba Acanthamoeba castellanii and a murine macrophage). To a large extent F. t. holarctica use similar mechanisms to persist predation by protozoa and to resist degradation by mammal macrophages. To summarize I found a link between predation resistant bacteria in aquatic environments and bacteria that are pathogenic to mammals. Further, I showed that different environmental conditions rapidly selects for PRB with either intracellular or extracellular lifestyles. This thesis provides insights regarding environmental conditions and biomarkers that can be used for assessment of aquatic environments at risk for spreading pathogenic bacteria.Medfinansiärer var även: Swedish Ministry of Defence (A4040, A4042, A404215, A404217), Swedish Minestry of Foreign Affairs (A4952), Swedish Civil Contingencies Agency (B4055)
6
Sexton, Jonathan D. "The Occurrence and Control of Pathogens on Fomites." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/312769.
Full textAbstract:
Microbes survive for an extended period of time on fomites. With new strains of pathogens constantly emerging, it is important to understand their survival and spread and to evaluate the efficiency of new disinfection methods. The purpose of this study was to determine the occurrence of pathogens on fomites, and evaluate different disinfection methods (household bleach and steam vapor). Fomites were sampled in a variety of environments for the presence of pathogens including methicillin intermediate- and resistant- Staphylococcus aureus, Clostridium difficile, Penecillium brevi-compactum, Alternaria alternata and novel H1N1 influenza A. Samples were assayed using both cultural and genetic techniques to determine the microbial occurrence. In disinfection studies, samples were collected before and after disinfectant application. Steam vapor was effective at reducing microbial occurrence by>90% with a minimal contact time of 10-20 seconds on hospital fomites. The material and shape of the surface had an effect on the reduction rate, due to access of the disinfecting agent. In addition, low levels of initial contamination limited the reduction rate. Many surfaces had a starting contamination level of less than 3 log10 and after disinfection the contamination levels, in 69% of the samples, were at or near the limit of detection. This suggests a higher reduction is feasible. Household bleach reduced the presence of mold spores and mycelium by >99% on gypsum-wall board. Reduction rates were influenced by the growth stage of mold, with the mycelium requiring additional disinfectant application to achieve the 99% reduction rate. Novel H1N1 influenza A was not recovered on any surfaces in day care facilities and elementary schools. This is consistent with previous studies looking at H1N1 influenza occurrence in similar environments, though it is different from H3N2 influenza A studies. Survival differences among varying influenza strains are expected to have an impact on pathogen spread and human health risks. Differences can be quantitatively evaluated and used to develop more advanced risk assessment models. Steam vapor and household bleach are effective at reducing risks of pathogens in the environment and are critical interventions in an overall strategy to minimize exposure and prevent disease.
7
Philibert, Marc-André C. "Mature, Water-Distribution Biofilm, Shelter Or Barrier for Pathogens?" University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1156430683.
Full text
8
Lacorazza, Camila. "Evaluation of environmental samples as a sampling method for detecting pathogens in zebrafish." Thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385875.
Full textAbstract:
Zebrafish are becoming increasingly popular to use in different kinds of research projects as research animals, replacing rodents in many fields. When using animals for research, it is important to keep track of the animal health in order to get reliable results. The purpose of the study was to investigate whether these pathogens could be found analyzing environmental materials with real-time PCR instead of euthanizing fish and submitting them for histopathology. Also, to see if any material differentiated from the rest regarding accessibility to work with in a routine diagnostic laboratory. This study was performed on environmental samples, such as filters, swabs, detritus and water, from a recirculating water system holding zebrafish. The pathogens analyzed were Mycobacterium chelonae, M. haemophilum, M. abscessus, M. marinum, M. fortuitum and Pseudoloma neurophilia, all common pathogens that can affect zebrafish. All materials tested gave at least one positive result for most of the pathogens tested. Two pathogens were not detected, M. marinum and M. abscessus. Due to poorly working PCR-system for M. fortuitum, the results for that bacteria were deemed inconclusive. The filter materials and the swabs of the filter materials gave the best results in this small study, although all materials gave satisfactory results. In conclusion this study shows that environmental samples can be used to detect pathogens in zebrafish, but larger studies should be performed to better evaluate which material is the best one to use.
9
Dulaney, D. R., Kurt J. Maier, and Phillip R. Scheuerman. "Data Requirements for Developing Effective Pathogen TMDLs." Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etsu-works/2938.
Full text
10
Manning, C. A., Kimberlee K. Hall, Brian G. Evanshen, Kurt J. Maier, and Phillip R. Scheuerman. "Occurrence of Fecal Pathogens E. coli 0517:H7 and Salmonella sp. in Relation to Fecal Indicator Concentrations Detected in Sinking Creek of the Boone Watershed." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/2949.
Full text
11
Arief, Ismail Shoieb Akaram. "Evaluation of biochar soil amendments in reducing soil and water pollution from pathogens in poultry manure." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117216.
Full textAbstract:
This project addresses concerns from the Canadian public about the quality of water in regions where many agricultural operations are located. Fecal coliforms are endemic in poultry and are difficult to eradicate from production facilities. Poultry manure is a reservoir of Campylobacter jejuni, Escherichia coli (including O157:H7) and Salmonella spp. Biochar, the charcoal produced from pyrolysis of biomass, is gaining global recognition due to its unique properties when applied as a soil amendment. Biochar could play an important role in controlling the mobility of pathogens in soil and water environment. Its half-life is estimated to be hundreds of years so it is expected that its role in reducing agricultural pollution could be very long-lasting, and hence very cost-effective.In this study we investigated the effectiveness of biochar in preventing the leaching of fecal coliforms into surface water. The target organisms in this study were Escherichia coli (E .coli) and total coliform. E. coli is widely recognized as the indicator organism for presence of fecal coliform and total coliforms to determine disinfection rate. The study was divided into two components, namely laboratory study and field study.In laboratory study, the effectiveness of three different types of biochar (variation based on production temperature, time and raw material) in adsorption and desorption of E. coli was studied. In adsorption test, a comparative analysis was carried out to understand the differences between biochar, soil amended biochar (soil to biochar ratio of 99:1) and un-amended soil in the removal of E. coli. The statistical analysis showed the adsorption of E. coli was significantly higher in the soil amended biochar treatment. The soil amended biochar and the un-amended soil treatments were further subjected to desorption to test their retention capacity. The statistical analysis showed that two types of soil amended biochars (slow pyrolysis biochar and fast pyrolysis biochar) retained E. coli significantly better. The adsorption capacity of biochar was directly proportional to its porosity and inversely proportional to its ash content. The two types of soil amended biochar were shortlisted based on sorption and retention capacity and were used as treatments in the field study.A sixty-day study was conducted using field lysimeters to evaluate the effectiveness of soil amended biochar in removing or reducing the leaching of fecal coliforms (E. coli) from poultry manure. Lysimeter with only soil was used as control and the shortlisted biochars (slow pyrolysis biochar and fast pyrolysis biochar) were used as treatments. In the biochar-amended treatments, the top 0.05 m of soil was amended with biochar in a proportion of 1:99 biochar:soil. Poultry manure was spread over the soil in all lysimeters. The lysimeters were protected from natural rainfall, and the simulated rainfall was applied as 4 events over a sixty day period. Both soil (3 sampling depths) and leachate samples were collected and analyzed at predetermined time intervals. In the experiment, E. coli and total coliform were found to leach down through the soil profiles, and their concentrations decreased with soil depth and time. The statistical analysis of soil samples and leachate showed that the concentration of E. coli in the treatments at the three sampling depths and in the leachate were significantly different from control (P ≤ 0.05), which is attributed to the effectiveness of the treatments in reducing the leaching of fecal coliforms. However, the concentration of total coliforms was significant (P ≤ 0.05) on certain intervals and insignificant in the others; this can be attributed to already present total coliforms in the soil system and effectiveness of the treatments to hinder coliform transport. Soil biochar amendment was thus seen to be effective in reducing the leaching of fecal coliforms through soil profiles and providing fecal coliforms free leachate.Ce projet répond aux préoccupations du public canadien au sujet de la qualité de l'eau dans les régions où de nombreuses exploitations agricoles sont présentes. Les coliformes fécaux sont endémiques chez les volailles et sont difficiles à éradiquer des sites de production. Le biochar, un charbon produit par pyrolyse de la biomasse, gagne de plus en plus de reconnaissance à l'échelle mondiale en raison de ses propriétés uniques lorsqu'il est utilisé comme amendement de sol. Sa demi-vie est estimée à des centaines d'années. Par conséquent, son rôle dans la réduction de la pollution agricole pourrait s'étendre sur une longue période.Dans cette étude, nous examinons l'efficacité du biochar dans la prévention de la lixiviation des coliformes fécaux dans l'eau de surface. Les organismes ciblés dans cette étude sont Escherichia coli (E coli.) et les coliformes totaux. E. coli est reconnu comme étant l'organisme indicateur de la présence de coliformes fécaux et les coliformes totaux comme étant révélateur du taux de désinfection. L'étude est composée de deux parties, l'une effectuée en laboratoire et l'autre sur le terrain.Dans l'étude en laboratoire, l'efficacité d'absorption et de désorption d'E. coli de trois différents types de biochar a été étudiée. Par le moyen de tests d'adsorption, une analyse comparative a été effectuée afin de déterminer la différence entre du biochar pur, un sol amendé par du biochar et un sol non-amendé dans leur efficacité d'élimination d'E. coli. Les analyses statistiques ont montré que le biochar comme amendement du sol joue un rôle important dans l'adsorption d'E. coli.Le sol amendé par du biochar et le sol non-amendé ont ensuite été soumis à un test de désorption afin de tester leur capacité de rétention. Les analyses statistiques ont démontré que deux types de sol amendés de biochar (l'un issu de la pyrolyse lente et l'autre de la pyrolyse rapide) retenaient E. coli. La capacité d'adsorption du biochar s'est révélée être directement proportionnelle à sa porosité et inversement proportionnelle à sa teneur en cendres. Les deux types de biochars ont été sélectionnés et utilisés comme traitements dans l'étude de terrain. L'étude de terrain a été réalisée sur des lysimètres pendant soixante jours afin d'évaluer l'efficacité du biochar dans l'élimination et la réduction du lessivage des coliformes fécaux (E. coli) venant du fumier de volaille. Le témoin contenait seulement du sol et le biochar sélectionné (l'un issu de la pyrolyse lente et l'autre de la pyrolyse rapide) a été utilisé comme traitement. Le biochar a été mélangé avec 5 cm de sol en partant de la surface (rapport de sol a biochar de 99:1). Le fumier de volaille a été répandu sur le sol dans tous les lysimètres. Les lysimètres ont été protégés de la pluie afin de simuler l'irrigation. L'irrigation a été simulée en 4 événements au cours des soixante jours. Le sol (3 profondeurs d'échantillonnage) et les échantillons de lixiviat ont été prélevés et analysés à des intervalles temporels prédéterminés. Dans cette étude, E. coli et les coliformes totaux se sont infiltrés à travers les profils de sol, et leurs concentrations ont diminués avec le temps et la profondeur du sol. Les analyses statistiques (P ≤ 0.05) des échantillons de sol et des lixiviats ont montré que la concentration d'E. coli dans les traitements aux trois profondeurs et dans le lixiviat étaient différente du contrôle, ce qui est attribué à l'efficacité des traitements de réduction du lessivage des coliformes fécaux. Cependant, la concentration de coliformes totaux était significatif (P ≤ 0.05) sur certains intervalles et insignifiant sur d'autres, ce qui peut être lié a une présence antérieure de coliformes totaux dans le sol et a l'efficacité des traitements qui suggèrent un taux de désinfection efficace. Le sol amendé de biochar a donc été considéré comme étant efficace dans la réduction du lessivage des coliformes fécaux a travers les profils de sol.
12
Mahajan, Rishab. "Quantitative assessment of exposure to enteric pathogens in drinking water." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258472492.
Full text
13
Basalla, Joseph. "Identifying biosynthetic gene clusters whose products inhibit cystic fibrosis derived pathogens." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1530795688583696.
Full text
14
Schmitz, Bradley William. "Reduction of Enteric Pathogens and Indicator Microorganisms in the Environment and Treatment Processes." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/612535.
Full textAbstract:
The reduction of pathogenic microorganisms is essential to minimize human health risks associated with the reuse, reclamation, and recycling of wastewater and the land application of biosolids (sewage sludge). The most advanced treatment technologies, as well as, the most representative methods and indicator organisms are necessary to ensure public safety. The goal of this dissertation is to assess advanced Bardenpho wastewater treatment technologies in regards to virus removal, suggest the most appropriate viral indicators of human fecal contamination and/or treatment process controls, and develop an updated method for enumerating Ascaris ova viability in land applied biosolids. Appendix A evaluates the incidence of 11 different virus types in sewage throughout a 12-month time period, and their subsequent reduction via advanced Bardenpho treatment processes. This study showed that wastewater treatment facilities utilizing advanced Bardenpho for secondary treatment are more effective at reducing viruses in wastewater than facilities utilizing conventional aeration basin and trickling filter processes. Appendix B develops a new method for determining the viability of Ascaris ova in land applied biosolids. In this method, early development stages prior to larval-development, are included in the estimation of potential viability. Comparisons between viability enumerations suggests that the conventional microscopy method, in which only ova containing motile larva are considered viable, underestimates the number of eggs that may progress to an infectious stage. Whereas, the method based on early-to-late stage development, considers the potential viability of all eggs, providing a more conservative approach.
15
Al-Maqtoofi, Marwan Yaseen Abdulmajeed. "Investigating host and environmental influences of Fusarium solani using a novel monoclonal antibody." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/23409.
Full textAbstract:
Human fungal infections among severely immunocompromised individuals have increased dramatically over the last 30 years and that coincidence with an expanding patient numbers of bone marrow and solid organ transplantation and those receiving aggressive cytotoxic chemotherapy for neoplastic diseases or immunosuppressive drugs. In recent years, many of opportunistic fungi have emerged as serious human pathogens and causing life-threatening infections of humans such as Fusarium species. Due to lack of a highly accurate diagnostic test for tracking the pathogenic Fusarium species, fusariosis is frequently misdiagnosed as aspergillosis. Delays in identification and differentiation of Fusarium spp. from other causative agents of hyalohyphomycetes associated with high morbidity and mortality rate among immunocompromised patients. This research aimed to develop a highly specific monoclonal antibody (mAb) using hybridoma technology to produce a highly genus-specific murine mAb ED7 that could be used for tracking and early detecting circulating Fusarium species antigens from other opportunistic pathogens. At present, a very little is known about the pathogenicity and interaction of human pathogenic F. solani and cells of the innate immune system like alveolar macrophages (AMØ), the residential innate immune cells of alveoli. For this reason, F. solani was genetically transformed with GFP gene and a model of immunoassay was developed to investigate the interactions of F. solani with AMØ that would allow studying the fungal pathogenicity, visualising and quantification of the pathogen during the process of macrophage phagocytosis. In addition, this model can be used to evaluate the effect of a mAb on fungal uptake by AMØ. Habitates providing direct human exposure to infectious propargules are largely unknown, but there is growing evidence that plumbing systems are sources of human pathogenic strains in the F. solani and F. oxysporum species complexes, the most common groups infecting humans. Using mAb ED7 specific to the Fusarium species, this work demonstrates how the mAb can be used as a powerful immunodiagnostic tool for accurately tracking the Fusarium species antigens in sink drain biofilms and water system samples containing mixed populations of human opportunistic filamentous and yeasts pathogenic fungi across a University campus and a tertiary care hospital. Specificity of the ELISA was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of culturable yeasts and moulds that were recovered using mycological culture, while translation elongation factor (TEF)-1 analysis of Fusarium isolates included FSSC 1-a, FOSC 33 and FDSC ET-gr, the most common clinical pathotypes in each group. The mAb ED7 is, therefore, suitable to be carried forward for use in diagnostic assays, such as the lateral flow device.
16
Harris, J. G. "The epidemiology of mildew and other barley pathogens in relation to environmental factors and integrated control." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355626.
Full text
17
Brazeau, Randi Hope. "Sustainability of Residential Hot Water Infrastructure: Public Health, Environmental Impacts, and Consumer Drivers." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26537.
Full textAbstract:
Residential water heating is linked to the primary source of waterborne disease outbreaks in the United States, and accounts for greater energy demand than the combined water/wastewater utility sector. To date, there has been little research that can guide decision-making with regards to water heater selection and operation to minimize energy costs and the likelihood of waterborne disease.
We have outlined three types of systems that currently dominate the marketplace: 1) a standard hot water tank with no hot water recirculation (STAND), 2) a hot water tank with hot water recirculation (RECIRC), and 3) an on-demand tankless hot water system with no hot water recirculation (DEMAND).
Not only did the standard system outperform the hot water recirculation system with respect to temperature profile during flushing, but STAND also operated with 32 – 36% more energy efficiency. Although RECIRC did in fact save some water at the tap, when factoring in the energy efficiency reductions and associated water demand, RECIRC actually consumed up to 7 gpd more and cost consumers more money. DEMAND operated with virtually 100% energy efficiency, but cannot be used in many circumstances dependent on scaling and incoming water temperature, and may require expensive upgrades to home electrical systems.
RECIRC had greater volumes at risk for pathogen growth when set at the lower end of accepted temperature ranges, and lower volumes at risk when set at the higher end when compared to STAND. RECIRC also tended to have much lower levels of disinfectant residual (40 -850%), 4-6 times as much hydrogen, and 3-20 times more sediment compared to standard tanks without recirculation. DEMAND had very small volumes of water at risk and relatively high levels of disinfection.
A comparison study of optimized RECIRC conditions was compared to the baseline modes of operation. Optimization increased energy efficiency 5.5 – 60%, could save consumers 5 – 140% and increased the disinfectant residual up to 560% higher disinfectant residual as compared to the baseline RECIRC system. STAND systems were still between 3 – 55% more energy efficient and could save consumers between $19 - $158 annual on water and electrical costs. Thus, in the context of “green” design, RECIRC systems provide a convenience to consumers in the form of nearly instant hot water, at a cost of higher capital, operating and overall energy costs.Ph. D.
18
Iker, Brandon Charles. "Application of Advanced Molecular Techniques in Applied Environmental Microbiology." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301699.
Full textAbstract:
Recent advancements in molecular biology such as next generation sequencing and more sensitive and rapid molecular detection methods like qPCR, have historically been developed for clinical applications in human genetics and for health care diagnostic purposes. The high demand for faster and more accurate molecular assays in the health care field has driven rapid development of inexpensive molecular techniques that when applied to the science of environmental microbiology, provides an unprecedented level of understanding of the microbial world around us. The goal of this dissertation is to begin to apply more advanced molecular technologies to problems in applied environmental microbiology. Appendix A is a brief literature review of next generation sequencing technologies for applications in environmental microbiology. Appendix B focuses on the development of a more robust virus nucleic extraction kit for the detection of viral genomes from environmental samples found to contain high concentrations of qPCR inhibitors, such as humic acids or heavy metals. Appendix C summarizes one of the largest virus surveys done in the US, using state of the art qPCR technologies in both wastewater influent and effluent from two wastewater treatment plants in the Southwest. Data suggests that traditional virus indicators may not be a viable tool to evaluate fecally impacted source water or virus removal during water treatment. The third study summarized in Appendix D, provides one of the first insights into the microbial ecology of biofilms utilized as biological treatment media using Roche 454 amplicon sequencing of the 16S rRNA gene.
19
Crowl, Rachel A. "Identifying Gene Regions That Produce Antagonistic Factors Against Multidrug Resistant Pathogens." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1625045409764561.
Full text
20
Patel, Kamal Thakor. "Reduction in Needlestick Injuries Using a Novel Package of Interventions." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7212.
Full textAbstract:
In 2015 Dr. Pratiksha Vaghela started the “Stop Poking Me” campaign which was aimed at curbing the increase in the number of needlesticks at the James A. Haley Veteran Affairs Hospital (JAHVA). The data for needlesticks was collected by the Occupational Medicine Clinic (OMC) between Oct 2013 and Oct 2016. We then obtained the original data from Dr. Vaghela’s project and compared the data to assess whether the new implementations have truly decreased the number of needlesticks. There was a 23.6% reduction in the number of needlesticks between 2013 and 2016 and even more importantly a 60.1% reduction between 2015 and 2016. Our project shows that the decrease correlates to the implementation of the “Stop Poking Me” campaign.
21
Stine, William S. "Survival of enteric pathogens on the surface of fresh produce and intake of heterotrophic bacteria in the United States." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280656.
Full textAbstract:
Disease due to the consumption of food contaminated with enteric microorganisms has been well established. The first study described in this dissertation was designed to determine the effect of relative humidity on the pre-harvest survival of enteric pathogens on the surfaces of fresh produce. Additionally, Clostridium perfringens was evaluated as an indicator of fecal contamination on fresh produce. Pathogenic and surrogate microorganisms, including Escherichia coli O157:H7, Escherichia coli ATCC 25922, Salmonella enterica subsp. enterica, Shigella sonnei, C. perfringens, coliphage PRD1, feline calicivirus (FCV), and hepatitis A virus (HAV), were inoculated onto the surfaces of cantaloupe, iceberg lettuce, and bell peppers. Experiments were conducted in a controlled environment chamber. Survival of microorganisms on the produce surfaces was not uniformly affected by relative humidity. However, due to the survival of all microorganisms at least 14 days in at least one experiment, measures should be taken to lessen the exposure of produce to fecal contamination as harvest time approaches. C. perfringens survived longer than all other bacteria and feline calicivirus in all experiments, with the exception of E. coli O157:H7 and S. enterica subsp. enterica on lettuce. This trend suggests that C. perfringens may be an acceptable indicator of bacterial contamination and survival in various environments and on different types of crops. The second study was conducted to determine the intake of heterotrophic bacteria by the average person in the United States from food and water. A literature review was conducted to determine the concentration of heterotrophic plate count (HPC) bacteria in foods and water from the household tap. Food items from grocery stores and fast food restaurants in Tucson, AZ were also evaluated for HPC bacteria. It was determined that in the United States, 0.048 to 4.5% of the typical consumer's HPC bacteria intake is derived from water consumed from the household tap. Therefore, HPC bacteria in tap water do not represent a significant source of the total HPC bacteria consumed in the average diet of individuals in the United States.
22
Wei, Xiaoping. "IDENTIFICATION AND REMEDIATION OF MICROBIAL CONTAMINANTS IN THE HEADWATERS OF AN AGRICULTURAL WATERSHED." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345550902.
Full text
23
Soto, Beltran Johana Marcela. "Assessing Efficacy of NanoCeram Filters For Virus Concentration From Water: Risk Assessment for Listeria and Salmonella in Food." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202530.
Full textAbstract:
Water quality, and therefore human health, may be significantly affected by the presence of pathogenic enteric microorganisms derived for improper disposal of wastewater to aquatic environments. Detection of waterborne viruses is complex due to the difficulties in concentrating the sample and then in detecting the virus by cell culture or molecular techniques. Methods used to concentrate enteric viruses from water have remained largely unchanged for nearly 30 years. The U.S. Environmental Protection Agency requires the use of 1MDS electropositive filters for concentrating enteric viruses from water; however, these filters are expensive for routine viral monitoring. The NanoCeram® filter, an electropositive cartridge filter, has been proposed as a new alternative for large volumes of water. The objective of the study was: to evaluate the effectiveness of NanoCeram® filters for the concentration of poliovirus-1 from wastewater samples and compare to 1MDS cartridge filters. This study suggested that NanoCeram® filters are a viable alternative to the use of 1MDS filters for viral monitoring in surface waters and wastewaters. L. monocytogenes outbreaks with Latin-style soft cheese have been well-documented; however, more information to characterize the human health risk associated with the consumption of queso fresco (QF) using unpasteurized milk is needed. The objectives of the study were: i) to evaluate the prevalence of Listeria, Escherichia coli, Salmonella and fecal coliforms in QF obtained from markets in the northwestern state of Sinaloa, Mexico, and ii) to address the human health impact associated with the consumption of QF contaminated with L. monocytogenes using quantitative microbial risk assessment (QMRA). The study suggested that QF produced in Culiacan, Sinaloa, Mexico have microbial loads above the maximum values recommended by the Official Mexican Regulations; and QMRA can be used to interpret microbial contamination data for impacts on public health.
24
Ozsoy, Gulcin. "An Investigation Of Agricultural Use Potential Of Wastewater Sludges In Turkey With Respect To Heavy Metals And Pathogens." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607739/index.pdf.
Full textAbstract:
Landfilling is the most common method that is used in the final disposal of sludge all around the world as well as in Turkey. However increasing sludge quantities and limited landfilling areas make this method invalid. Use of sludge in agriculture presents a possible alternative for disposal. However, it also poses some risks to be evaluated.
In this respect, it is important to identify heavy metal and pathogen content of sewage sludges because of their adverse health effects. This study aims to determine the heavy metal contents and pathogen levels of sludges from four different wastewater treatment plants of Turkey. The selection of plants was done according to the different treatment technologies applied to wastewater and sludge in those plants. Heavy metal analysis of sludges was conducted by using microwave assisted digestion procedure and pathogen levels were done by methods from Standard Methods (SM), ISO and USA EPA.
After sampling and analysis, the results show that all the related metal concentrations are below the values that are set in the Soil Pollution Control Regulation of Turkey. However in sludges from Ankara and Kayseri wastewater treatment plants, Zinc and Nickel concentrations should be tracked carefully. The results related with pathogen levels in sludges show that dewatered sewage samples taken from Ankara, Kayseri and Kemer wastewater treatment plants do not meet neither Class A nor Class B fecal coliform limits set by USA EPA however lime stabilized dewatered sludge from izmir wastewater treatment plant meet the requirement. In addition, Salmonella levels in Kayseri dewatered sludges exceed the limit value.
25
Rea, Christopher L. "Fate and Transport of Avian-Associated Pathogens in Western Lake Erie Beaches." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385999641.
Full text
26
Subasinghe, R. P. "Studies on the effects of environmental factors and selected pathogens on morbidity and mortality of hatchery reared Oreochromis mossambicus (Peters) eggs and fry." Thesis, University of Stirling, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375402.
Full text
27
Pongmala, Khemngeun. "Influence des propriétés physiques et chimiques du sol et de leur variation saisonnière sur l'occurrence et la distribution de Burkholderia pseudomallei dans une rizière au centre du Laos." Electronic Thesis or Diss., Toulouse 3, 2022. http://thesesups.ups-tlse.fr/5342/.
Full textAbstract:
Burkholderia pseudomallei (BP) bactérie commune des sols tropicaux, provoque une maladie grave, la mélioïdose. Cette thèse, basée sur un travail de terrain dans le centre de la RDP Lao où BP est endémique, vise à clarifier les déterminants de la distribution de BP dans le sol en fonction des conditions biogéochimiques du sol et climatiques, à des échelles emboîtées. PB a été identifiée dans le sol jusqu'à 300 cm de profondeur, à des concentrations variables (maximales en dessous de 100 cm), à la fois à l'échelle du millimètre, en lien avec l'état d'oxydation du fer, et à l'échelle du profil du sol. La variabilité saisonnière des concentrations de BP, plus marquée près de la surface qu'en profondeur, est cohérente avec sa persistance accrue dans les couches saturées d'eau tout au long de l'année. Cette thèse démontre l'importance de considérer la complexité du sol pour mieux comprendre l'écologie de BPBurkholderia pseudomallei (BP) a pathogenic bacterium found in tropical soils, causes a severe disease, melioidosis. This thesis, based on field work in the main region of BP endemicity in Lao PDR, aims to clarify the determinants of BP distribution in soil. We applied a multi-scale approach to characterize the distribution of BP in relation with soil physico-chemical variability and highlight seasonal variations in BP distribution. BP occurred at all soil depths down to 300 cm but its concentrations varied drastically, both at the millimetre scale, concomitantly with the oxidation state of iron, and at the soil profile scale, unexpectedly reaching peak values below 100 cm. Seasonal variability of BP concentrations was higher in shallow than deep soil horizons, consistent with increased BP persistence in layers saturated with water year round. This thesis demonstrate the importance of considering the complexity of soil to better understand the ecology of BP
28
Demitry, Mariana. "Evaluating Water Filtration and Disinfection for Household, Using Slow Sand Filters plus Solar Disinfection." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6911.
Full textAbstract:
In this research, a household water treatment system was built and evaluated as a trial for improving the drinking water quality of the Nile River for the low-income communities. The system consisted of household-scale slow sand filters, and transparent polyethylene terephthalate-bottles for solar disinfection. The evaluation of the system depended on the removal/inactivation of some surrogates for the reference pathogens, and turbidity. The reference pathogens are pathogens specified by the World Health Organization to evaluate the efficiency of the household water treatment options. They were chosen to represent the classes of pathogens in water (bacteria, viruses, protozoa). The surrogates used in the evaluation of the system are Escherichia coli (E.coli), Clostridium perfringens and Escherichia coli bacteriophage (MS2). The candidate surrogates are also specified by the World Health Organization.
The designed household-scale slow sand filter was very efficient in removing the different turbidity levels to ≤0.4NTU. The evaluated system is classified as highly protective because it was able to achieve higher than 4 log removal for E.coli and Clostridium perfringens, and higher than 5 log removal for MS2.
29
Marcantonio, Matteo [Verfasser], Birgit [Akademischer Betreuer] Kleinschmit, Birgit [Gutachter] Kleinschmit, and Chris [Gutachter] Barker. "Environmental modelling and spatial ecology with focus on invasive Aedes mosquitoes and emergent mosquito-borne pathogens / Matteo Marcantonio ; Gutachter: Birgit Kleinschmit, Chris Barker ; Betreuer: Birgit Kleinschmit." Berlin : Technische Universität Berlin, 2017. http://d-nb.info/115627107X/34.
Full text
30
Mraz, Alexis Layman. "Forecasting in the Unseeable: A Mixed Methods Model of Planktonic and Biofilm-Bound Legionella pneumophila in Building Water Systems." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu154350645678355.
Full text
31
Sassi, Hannah Pau. "Evaluation of Viral Inactivation and Survival in Three Unique Environments, through the Use of MS2 Coliphage as a Surrogate." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/613222.
Full textAbstract:
Surrogate organisms have been used to study highly pathogenic organisms, or organisms that cannot be cultured in the laboratory. Surrogates are selected based on multiple similarities to the pathogen, such as morphology, genome size and structure, and environmental characteristics. This dissertation utilized MS2 coliphage as a surrogate for norovirus and Ebola virus in three environments. MS2 is an icosahedral, single-stranded RNA bacteriophage. It is a male-specific coliphage that infects the bacteria Escherichia coli. Its properties, such as morphology and survival in the environment, have been likened to those of many enteric viruses. Because of this, it has been used as a surrogate for pathogenic enteric viruses for disinfection testing on surfaces, in water and in food; modeling the movement and survival of pathogens in different environments; and transfer properties from surfaces. This dissertation utilized MS2 as a surrogate in three different studies. In the first, MS2 is used as a surrogate for human enteric viruses in irrigation canals to predict the re-suspension of pathogenic viruses from bed sediment into overlying irrigation water using a flume to re-create field conditions in the laboratory. MS2 re-suspension into the overlying water was characterized at varying flow rates and velocities using two sediment types. Its overall re-suspension was not statistically significantly different (p > 0.05) between flow rates. The additional studies in this dissertation used MS2 as a surrogate for Ebola virus in human waste. Ebola virus is a BSL-4 organism that is spread through direct contact with bodily fluids. It is found in bodily fluids in concentrations between 10^5.5 and 10⁸ genome copies per milliliter. In the first study using MS2 as a surrogate for Ebola virus, efficacies of four disinfectants were tested using 10¹² PFU of MS2 in one liter containing 2.25% (w/v) organic matter at three contact times (1, 15 and 30 minutes). The purpose of this study was to assess the disinfectants on reducing virus in waste before toilet flushing. Peracetic acid and quaternary ammonium formulation were found to reduce the concentration of MS2 in the toilet bowl the fastest (within one minute) with the greatest reduction (2.26 and 1.99 log₁₀), when compared with the other disinfectants. Reductions observed from hydrogen peroxide were significantly less than those from peracetic acid and quaternary ammonium (p < 0.05). The contamination of restroom surfaces by MS2 was also evaluated after toilet flushing with and without disinfectant treatment. All four disinfectants were found to significantly reduce the viral concentrations on fomites after 15 minutes of contact (p < 0.05). Despite disinfectant use, three sites were contaminated in 100% of trials (N = 18). These were the toilet bowl rim, the toilet seat top and underside. The final study evaluated the inactivation of MS2 and several other viruses by thermophilic and mesophilic anaerobic digestion. Little information is available on the influence of the wastewater treatment process, specifically anaerobic digestion, on emerging viruses, such as Ebola virus. It is important to evaluate this process due to the environmental disposal and discharge of wastewater and solids into the environment. All viruses were recoverable after mesophilic digestion (reductions from 1.8-6.6 log₁₀ per mL), except the lipid-containing bacteriophage Φ6. Thermophilic digestion inactivated all viruses significantly (p = 0.0011) more than mesophilic digestion. The reductions by thermophilic digestion ranged from 2.8-7.1 log₁₀ per mL. The inactivation between the initial concentration and both digestion types was statistically significant (p = 0.007).
32
Benschop, Jacqueline. "Epidemiological investigations of surveillance strategies of zoonotic Salmonella : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University." Massey University, 2009. http://hdl.handle.net/10179/1025.
Full textAbstract:
This thesis is concerned with the application of recently developed epidemiological and statistical tools to inform the optimisation of a national surveillance strategy of considerable importance to human health. The results of a series of epidemiological investigations of surveillance strategies for zoonotic Salmonella are presented. Salmonella are one of the most common and serious zoonotic foodborne pathogenic bacteria globally. These studies were motivated by the increasing focus on the cost-effectiveness of surveillance while maintaining consumer confidence in food supply. Although data from the Danish Salmonella surveillance and control programme has been used in these investigations, the techniques may be readily applied to other surveillance data of similar quality. The first study describes the spatial epidemiological features of Danish Salmonella surveillance and control programme data from 1995 to 2004, using a novel method of spatially adaptive smoothing. The conditional probability of a farm being a case was consistently high in the the south-west of Sonderjylland on the Jutland peninsula, identifying this area for further investigation and targeted surveillance. The identification of clustering of case farms led into the next study, which closely examines one year of data, 2003, for patterns of spatial dependency. K-function analyses provided evidence for aggregation of Salmonella case farms over that of all farms at distances of up to six kilometres. Visual semivariogram analyses of random farm-level effects from a Bayesian logistic regression model (adjusted for herd size) of Salmonella seropositivity, revealed spatial dependency between pairs of farms up to a distance of four kilometres apart. The strength of the spatial dependency was positively associated with slaughter pig farm density. We describe how this might inform the surveillance programme by potentially targeting herds within a four kilometre radius of those with high levels of Salmonella infection. In the third study, farm location details, routinely recorded surveillance information, and industry survey data from 1995 were combined to build a logistic seroprevalence model. This identified wet-feeding and specific pathogen free herd health status as protective factors for Salmonella seropositivity, while purchasing feed was a risk factor. Once adjusting for these covariates, we identified pockets of unexplained risk for Salmonella seropositivity and found spatial dependency at distances of up to six km (95% CI: 2–35 km) between farms. A generalised linear spatial model was fitted to the Jutland data allowing formal estimation of the range of spatial correlation and a measure of the uncertainty about it. There was a large within-farm component to the variance, suggesting that gathering more farm level information would be advantageous if this approach was to be used to target surveillance strategy. The fourth study again considers data from the whole study period, 1995 to 2004. A detailed temporal analysis of the data revealed there was no consistent seasonal pattern and correspondingly no benefit in targeting sampling to particular times of the year. Spatiotemporal analyses suggested a local epidemic of increased seroprevalence occured in west Jutland in late 2000. Lorelogram analyses showed a defined period of statistically significant temporal dependency, suggesting that there is little value in sampling more frequently than every 10 weeks on the average farm. The final study uses findings from the preceding chapters to develop a zero-inflated binomial model which predicts which farms are most at risk of Salmonella, and then preferentially samples these high-risk farms. This type of modelling allows assessment of similarities and differences between factors that affect herd infection status (introduction) and those that affect the seroprevalence in infected herds (persistence and spread). The model suggested that many of the herds where Salmonella was not detected were infected but at a low prevalence. Using cost and sensitivity, we compared the results with those under the standard sampling scheme based on herd size, and the recently introduced risk-based approach. Model based results were less sensitive, but showed significant cost savings. Further model refinements, sampling schemes, and the methods to evaluate their performance are important areas for future work, and should continue to occur in direct consultation with Danish authorities.
33
Rajkumar, Yasmin. "The fate of microbial contaminants in the subsurface with a South African case study." Thesis, Online Access, 2009. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_2581_1277756469.pdf.
Full text
34
James, Adèle. "Ecology, evolution and virulence of environmental vibrios." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS477.pdf.
Full textAbstract:
Les changements globaux provoquent une augmentation des infections associées aux Vibrio. Les vibrioses affectent les humains, mais aussi des animaux marins. Un problème majeur est le manque de connaissances sur les vibrios présents dans l’environnement. Pour mieux comprendre et gérer ces maladies, nous nous sommes intéressés à l’écologie, l’évolution et la virulence de ces agents infectieux. Tout d’abord, nous avons montré que dans la nature, certains génotypes de Vibrio sont virulents pour les huîtres et que leurs mécanismes de virulence sont impliqués dans la différentiation écologique de ces souches. En France, les parcs ostréicoles font face à des évènements de mortalités massives associés à la présence d’un virus et de bactéries du genre Vibrio. Nous avons montré que le virus n’est ni essentiel, ni suffisant pour induire de fortes mortalités, contrairement aux vibrios qui jouent un rôle majeur. Les huîtres juvéniles malades sont toujours infectées par plusieurs populations, mais une seule, Vibrio crassostreae, est détectée en abondance. La virulence de cette population dépend d’un système de sécrétion de type IV codé par un plasmide conjugatif. Nos résultats suggèrent que V. crassostreae était un colonisateur peu virulent et que l’invasion du plasmide l’a rendu hautement pathogène. La distribution restreinte du plasmide de virulence suggère qu’il a été sélectionné par les hautes densités d’élevages. Enfin, nous avons montré que le transfert ou la sélection du plasmide était favorisé dans l’huître, suggérant que l’huître représente une niche propice aux transfert latéraux de gènes. Ce travail pourra permettre le développement d’outils de diagnostic et le suivi épidémiologique des vibrios pathogènesGlobal change, including anthropogenic activities, have resulted in an increase in the incidence of Vibrio-associated illnesses. These diseases not only affect humans but also marine animals. Despite strong ecological and economic consequences, little is known about population structure and virulence mechanisms of vibrios in the environment. To better understand and manage those diseases, we explored the ecology, the evolution and the virulence of these infectious agents. First, we found that some environmental strains were virulent towards oyster and we identified original virulence mechanisms related to their ecology and evolution. In France, oyster-farms are facing massive mortality events associated with the presence of a virus and bacteria of the genus Vibrio. We showed that the virus appears neither essential nor sufficient to cause high mortality rates contrary to the vibrios that play a major role. Juvenile diseased oysters were always co-infected by several populations, but only one, Vibrio crassostreae, was detected systematically and in abundance. Its virulence is dependent on a type VI secretion system that is carried by a conjugative plasmid. Our results suggest that V. crassostreae first differentiated into a low-virulent oyster colonizer and turned into a pathogen after acquisition of the virulence plasmid. The narrow distribution of the plasmid suggests that it has been selected by high density farming areas. Finally, we showed that the plasmid transfer or selection was enhanced in oysters, which suggests that oysters represent a niche for horizontal gene transfer. Overall, this work can lead to the development of diagnostic tools and epidemiological monitoring of pathogenic vibrios
35
Carlander, Anneli. "Assessment of microbial health hazards associated with wastewater application to willow coppice, coniferous forest and wetland systems /." Uppsala : Department of Crop Production Ecology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200629.pdf.
Full text
36
Rosenblum, James S. "The Relationships of Pathogenic Microbes, Chemical Parameters, and Biogas Production During Anaerobic Digestion of Manure-based Biosolids." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376929611.
Full text
37
Verbyla, Matthew Eric. "Pathogen Removal in Natural Wastewater Treatment and Resource Recovery Systems: Solutions for Small Cities in an Urbanizing World." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6044.
Full textAbstract:
Sanitation, renewable energy, and food security are among the most pressing global development needs of the century, especially for small cities with rapid population growth. Currently, 53% of the world’s population either lacks access to improved sanitation or discharges fecal waste to the environment without treatment. Furthermore, 80% of food consumed in developing regions is produced by 500 million small farms, and while many of them are still rain-fed, irrigated agriculture is increasing. The post-2015 Sustainable Development Goals, recently adopted by the United Nations, include targets to address the water-energy-food nexus. Wastewater reuse in agriculture can be an important solution for these goals, if it is done safely. Globally, 18 – 20 million hectares of agricultural land are irrigated with wastewater, but much is untreated, unregulated, or unsanctioned, causing concerns and uncertainty about health risks.
There is a need to better understand pathogen removal in natural and non-mechanized wastewater treatment systems, such as waste stabilization ponds (WSPs) and upflow anaerobic sludge blanket (UASB) reactors, which are commonly used in small cities and towns. Riverbank filtration (RBF) is also a natural technique used by farmers in developing countries to treat surface water polluted with untreated sewage, but pathogen removal in these systems has seldom been assessed in developing countries. The focus of this dissertation is on pathogen removal in natural and non-mechanized wastewater treatment and reuse systems, to evaluate the health implications of water reuse for irrigation, with the following three objectives: 1) assess the current understanding of virus removal in WSP systems through a systematic review of the literature; 2) measure the removal of viruses and their association with particles in systems with WSPs, UASB reactors, or both; and 3) assess the fate and transport of pathogens and fecal indicators in wastewater treatment systems with direct and indirect reuse for irrigation to estimate microbial risks.
To advance the understanding of virus removal in WSP systems, a comprehensive analysis of virus removal reported in the literature from 71 different WSP systems revealed only a weak to moderate correlation of virus removal with theoretical hydraulic retention time (HRT). For each log10 reduction of viruses a geometric mean of 14.5 days of retention was required, but the 95th percentile of the data analyzed was 54 days. Also, whereas virus-particle association and subsequent sedimentation has been assumed to be an important removal mechanism for viruses in WSPs, the literature review revealed a lack of evidence to confirm the validity of this assumption.
The association of human adenovirus (AdV) with wastewater particles was assessed in five full-scale wastewater treatment systems in Bolivia, Brazil, and the United States (two with only WSPs, two with a UASB reactor and WSPs, and one with only UASB reactors). A mesocosm study was also conducted with WSP water from one of the full-scale systems, and some samples were also analyzed for pepper mild mottle virus (PMMoV), F+ coliphage, culturable enterovirus (EV), norovirus (NoV), and rotavirus (RV). Results indicate that WSPs and UASB reactors affect virus-particle associations in different ways, which may differ for different viruses. In UASB reactor effluent, PMMoV was more associated with particles <180 >µm, showed no indication of settling in subsequent ponds, and appeared to degrade in pond sediments after 5 days. In contrast, AdV in UASB reactor effluent was associated with small and large particles, and in subsequent ponds, particle-associated AdV showed evidence of possible settling or more rapid decay at the water surface. AdV and culturable EV were also more volumetrically-concentrated in UASB reactor sludge than they were in untreated sewage, WSP water, UASB effluent, and WSP sediments, indicating that the reactors may cause these viruses to become entrapped and concentrated in granular sludge. Some viruses may be removed in the sludge, but others exit the reactors in solution and attached to particles. The resuspension of pellets from centrifuged UASB reactor sludge samples in an eluant buffer indicated reversible AdV association with granular sludge, but some associations with particles in solution may not be reversible.
The fate and transport of pathogens and fecal indicators was assessed in Bolivia for two WSP systems with direct reuse for irrigation, and one on-farm RBF system used to treat surface water polluted by untreated sewage. In the WSP systems, despite HRTs of 10 days, pathogen and fecal indicator removal was generally ≤1-log10, possibly due to overloading and short-circuiting from sludge accumulation. The RBF system provided removals on the order of 2-log10 for protozoan parasites, 3-log10 or more for viruses, and 4-log10 or more for bacteria. The use of RBF also reduced cumulative estimated health burdens associated with irrigated lettuce. Irrigation of lettuce with untreated river water caused an estimated disease burden that represents 37% of the existing burden from acute diarrhea in Bolivia; when RBF was used, this decreased to only 1.1%, which is not epidemiologically-significant, and complies with the World Health Organization guidelines. Ratios of concentrations of microorganisms in irrigation water to their respective concentrations in soil or crops were calculated, to assess transfer from irrigation water to soil or crops. These ratios (with units mL g-1) were generally < 0.1 mL g-1 for coliphage, between 1 and 100 mL g-1 for Giardia and Cryptosporidium, and generally between 100 and 1,000 mL g-1 for helminth eggs. Higher ratios could indicate more efficient transfer from water to soil or crops, longer persistence in soil or on crops, or slower leaching away from soil or crops.
The results from this research demonstrate that pathogen removal in full-scale natural wastewater treatment systems happens via complex mechanisms that vary with respect to pathogen type, treatment systems configuration, and other environmental and operational parameters. Future research and innovation efforts should focus on the use of a combination of natural and non-mechanized technologies, surface-flow systems (e.g., WSPs) and subsurface systems (e.g., RBF), applied at both semi-centralized (e.g., wastewater treatment plant) and decentralized levels (e.g., on farms), to evaluate how this affects the efficiency and resiliency of pathogen removal. Also, future research is needed to further elucidate reasons for the observed differences in virus-particle associations in natural wastewater treatment systems.
38
Moura, Alexandre Carvalho de. "Aspectos microbiológicos do sistema água residuária da suinocultura-solo." Universidade Estadual do Oeste do Parana, 2015. http://tede.unioeste.br:8080/tede/handle/tede/209.
Full textAbstract:
Made available in DSpace on 2017-05-12T14:47:09Z (GMT). No. of bitstreams: 1
Alexandre_ Carvalho de Moura.pdf: 1339346 bytes, checksum: c6c44c93413060ef90d9799424d1bb5d (MD5)
Previous issue date: 2015-02-24wastewater use in agricultural soils has been adapted as an important pratice for agriculture. Due to the reduction of the availability of the quality of water resources is becoming increasingly important to add value to the use of water. The swine wastewater is rich in organic matter, composed of various elements of chemical origin, physical and biological. Its addition in soil and water resources without previous studies and knowledge of its components, can cause changes in the soil, contamination of surface and groundwater, biology changes in these environments, as well as the contribution and accumulation of groups of microorganisms in the environment, including pathogens. Most studies on swine wastewater, mainly in Brazil, are restricted to its physical and chemical components, evaluating its impact directly on the ground, water bodies or in plant productivity. Few studies focus on the microbial composition of this type of waste and especially on the risk of environmental contamination by pathogenic microorganisms or even on the impact of this element in the soil microbial community. Thus these animal manure may have an important role as initiators of infectious diseases in animals and humans. Thus, this thesis consists of two papers. In the first article, a study was done to check the bacterial composition present in swine wastewater, and to verify the possibility of eliminating these microorganisms through the main anaerobic treatment systems used in Brazil. It was evaluated in particular pathogenic microorganisms of gastrointestinal origin of the pigs and microbial environmental markers. The wastewater samples were taken from pig farms that use bio-manure storage tanks and digesters as treatment methods for the waste. The results clearly showed the presence of biomarkers and pathogens in swine wastewater. Despite the possibility of decrease of certain microbial groups throughout the stages of the treatment process, no elimination of pathogens in either treatment systems. Thus, demonstrates the possibility of the spread of pathogens and microorganisms in the environment. In the second paper, the objective was to evaluate the effect of application of swine wastewater associated with mineral fertilizer in agriculture, after a long time of application of swine wastewater in the soil microbial community. Thus, samples were collected from soils after 18 production culture cycles, with the application of wastewater from pig farms and assessed the quantitative effects (basal respiration, microbial biomass and metabolic quotient) and qualitative (DGGE, biodiversity indices, correlation between the chemical conditions and soil microbial activity) in the soil microbial community. The results showed that the application of swine wastewater, especially after long time and in higher concentrations, can change the dynamics of soil microbial community, impacting the dump site. The results of these studies show the need for further studies to apply this type of waste in agricultural soils, in order to minimize the risk of environmental contamination and/ or spread of pathogens.
A utilização de água residuária em solos agrícolas vem sendo praticada como importante opção para agricultura. Devido à redução na disponibilidade de recursos hídricos, a reutilização de água residuária vem ganhando espaço na agricultura com a agregação de valor para o uso de água. A água residuária da suinocultura é rica em matéria orgânica, composta por diferentes elementos de origem química, física e biológica. Sua adição no solo e recursos hídricos, sem estudos prévios e conhecimento de seus componentes, pode provocar contaminação de águas superficiais e subterrâneas, alterações da biologia destes ambientes, bem como o aporte e acúmulo de grupos de microrganismos no ambiente, incluindo patógenos. A maior parte dos estudos sobre água residuária da suinocultura, principalmente no Brasil, se restringe aos seus componentes físicos e químicos, avaliando seu impacto diretamente sobre o solo, corpos d´agua ou na produtividade vegetal. Poucos estudos se concentram na composição microbiana deste tipo de resíduo e principalmente sobre o risco de contaminação ambiental por microrganismos patogênicos ou mesmo sobre o impacto deste elemento na comunidade microbiana do solo. Desta forma estes dejetos animais podem apresentar importante papel como iniciadores de doenças infecciosas em animais e seres humanos. Este trabalho de tese é constituído de dois artigos. No primeiro artigo, foi feito um estudo para verificar a composição bacteriana presente na água residuária da suinocultura, bem como verificar a possibilidade de eliminação destes microrganismos através dos principais sistemas de tratamento anaeróbicos utilizados no Brasil. Foram avaliados em especial os microrganismos patogênicos, de origem gastrointestinal dos suínos e bioindicadores microbianos. As amostras de água residuária utilizadas foram provenientes de granjas que utilizavam de sistemas anaeróbicos com esterqueiras e biodigestores no tratamento do resíduo. Os resultados obtidos mostraram claramente a presença de coliformes, mesofilos aeróbios, bolores e leveduras, enterococos e patógenos na água residuária da suinocultura. Apesar da possibilidade de decréscimo de determinados grupos microbianos ao longo das etapas dos processos de tratamento, não houve eliminação de patógenos em nenhum dos dois sistemas de tratamento, o que pode possibilitar a disseminação de microrganismos e patogenos no meio ambiente. No segundo artigo, o objetivo foi avaliar o efeito da aplicação da água residuária da suinocultura associada a adubação mineral, em área agrícola, após longo tempo de aplicação, na comunidade bacteriana do solo. Assim, foram coletadas amostras de solo com 18 ciclos de produção, com aplicação de água residuária de suinocultura e avaliados os efeitos quantitativos (respiração basal, biomassa microbiana e quociente metabólico) e qualitativos (DGGE) na comunidade bacteriana do solo. Os resultados mostraram que a aplicação de água residuária da suinocultura, principalmente após longo tempo e em concentrações maiores, pode alterar a dinâmica da comunidade bacteriana do solo, impactando no local de despejo. Os resultados dos artigos mostram a necessidade de maiores estudos para aplicação deste tipo de resíduo na agricultura, a fim de minimizar os riscos de contaminação ambiental e ou disseminação de patógenos.
39
Hsu, Tsung-Ta David. "Public Health Ecosystem Services and Potential Concerns of Freshwater Wetlands." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439487401.
Full text
40
Effendi, Irwan. "Survival of Aeromonas salmonicida in the marine environment." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1369.
Full text
41
Sarkar, Payal. "Occurrence and Inactivation of Emerging Pathogens in the Environment." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194623.
Full textAbstract:
Emerging pathogens are organisms whose incidence has increased within the past two decades. In the last 40 years, several pathogens have emerged to cause infectious waterborne and foodborne diseases, thus causing a significant public health concern. Enterobacter sakazakii and Naegleria fowleri are emerging pathogens that have been documented to cause fatal infections. E. sakazakii is an emerging foodborne pathogen that represents a significant health risk by causing infections resulting in septicemia, meningitis and necrotizing enterocolitis in neonates, premature infants and also elderly immunocompromised individuals. Naegleria fowleri is a water-based protozoan flagellate that is the cause of primary amoebic meningoencephalitis; a fatal disease that mostly infects children and young adults through water-related recreational activities. The focus of this dissertation is to identify environmental reservoirs of Enterobacter sakazakii and to determine inactivation strategies to control Naegleria fowleri by chlorine and ultraviolet disinfection. In Appendix A, samples from various household kitchens were collected to determine the presence of E.sakazakii. The highest percentage of E.sakazakii was isolated from kitchen sponges (8%; n=50) and dishrags (10%; n=50). This study provided information on the presence of E.sakazakii on environmental surfaces in the kitchen. In Appendix B, our recent research has determined that N. fowleri is present in 8% (n=143) of municipal drinking water wells in central and southern Arizona. Therefore, guidelines need to be established for treatment of water with various disinfectants to control the growth and proliferation of N.fowleri. In Appendix C, the Ct values (concentration (mg/l) × exposure time) for chlorine inactivation of N. fowleri trophozoites and cysts were determined using the Efficiency Hom Kinetic Model (EHM). The Ct values for 99% inactivation of trophozoites and cysts were estimated to be 9 and 31, respectively. The ultraviolet light dose required for the 99% inactivation of N.fowleri trophozoites and cysts was determined to be 63 mW.sec/cm² and 13 mW.sec/cm², respectively.
42
Boufleuer, édela Marisa dos Santos. "Diversidade e perfil de resistência a antimicrobianos de bactérias isoladas em pisciculturas com diferentes densidades de estocagem." Universidade Estadual do Oeste do Parana, 2015. http://tede.unioeste.br:8080/tede/handle/tede/1821.
Full textAbstract:
Made available in DSpace on 2017-07-10T18:01:57Z (GMT). No. of bitstreams: 1
Edela M dos Santos Boufleuer.pdf: 1243031 bytes, checksum: 7e08e3f33bb967a1e04093cb724e3762 (MD5)
Previous issue date: 2015-08-13Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The work aimed to characterize the bacterial diversity and profile of antimicrobial resistance in fish breeding with different densities. Water samples were collected in four points (amount, input, output, and downstream) of nurseries of three fish breeding, each composed of a different stocking density (4 fish by squared meter, 8 fish by squared meter, 10 fish by squared meter). The parameters analized to determine water quality were dissolved oxygen, temperature, water pH, electrical conductivity, phosphorus, ammonia, biochemical oxygen demand, chemical oxygen demand and organic matter. Heterotrophic mesophilic bacteria were isolated as well as their total amount was determined. Subsequently, the identification of isolated species was carried out and then subject ted to qualitative analysis of front resistance profile to seven commercial antibiotics. The set of physical and chemical variables were summarized in three main components by main component analysis. In the first main component (ammonia, phosphorus, organic matter, water temperature and dissolved oxygen), there was a greater amount in the breeding ground than what was expected, where as the dissolved oxygen was higher than downstream. The second main substance (nitrite) showed a difference if compared to the inside of the breeding grounds, being higher than downstream. The interaction between breeding sites and densities, as well as the main density effect were not significant in the first two components. The third component (electrical conductivity) varied significantly between the sites, making it possible to notice that the amount was lower, and it experienced a signify cant raise inside the breeding ground sand went on to an intermediate value downstream. Concerning the values of density, it was possible to realize that the electrical conductivity was higher in the tanks which had the highest concentration of fish. From the 407 that were isolated, 55 bacterial species were recognized and identified, being part of eleven different families. The Enterobacteriaceae family was the one that prevailed among the evaluated densities, followed by Alcaligenaceae. The stocking density of 4 fish by squared meter presented significant statistical differences, with lower frequence of families. A great amount of resistant bacteria was observed, and their resistance was mainly to ampicillin and erythromycin, while fewer than 15% of the isolated were resistant to chloramphenicol and gentamicin. Among the isolated that were analyzed, 96% showed multiple antimicrobial resistance index higher or equal 0,2. The intensification of systems promoted the increase of bacteria concentration, there wasn't relation to the physical and chemical variables was identified a variety of bacterial species and there was high rate of resistance and multidrug resistance to antimicrobials tested.
O trabalho teve o objetivo de caracterizar a diversidade bacteriana e o perfil de resistência a antimicrobianos em pisciculturas com diferentes densidades. Foram coletadas amostras de água em quatro pontos (montante, entrada, saída e jusante) de viveiros de três pisciculturas, cada uma composta por uma densidade de estocagem diferente (4 peixes/m2, 8 peixes/m2 e 10 peixes/m2). Os parâmetros analisados para qualidade da água foram oxigênio dissolvido, temperatura, pH, condutividade elétrica, pH, fósforo, amônia, demanda bioquímica de oxigênio (DBO), demanda química de oxigênio (DQO e matéria orgânica. Também foram isolados e feito a contagem total de bactérias mesófilas heterotróficas. Posteriormente, foi realizada a identificação das espécies isoladas, em seguida submetidas a análise qualitativa do perfil de resistência frente a sete antibióticos comercial. O conjunto de variáveis físicas e químicas foi sumarizado em 3 componentes principais pela análise de componentes principais (ACP). No primeiro componente principal (amônia, fósforo, matéria orgânica e temperatura da água e oxigênio dissolvido) foi identificado valores superiores dentro do viveiro, ao passo que o oxigênio dissolvido foi superior a jusante. O segundo componente principal (nitrito), apresentou diferença em relação ao interior dos viveiros, sendo superior a jusante. Interação entre locais e densidade, bem como efeito principal da densidade não foram significativos no dois primeiros componentes. Já o terceiro componente (condutividade elétrica) variou significativamente entre os locais, observando que foi inferior a montante, sofreu uma elevação significativa no interior dos viveiros e passou a um valor intermediário a jusante. Para as densidades, a condutividade elétrica foi superior nos tanques que apresentaram maiores concentrações de peixes. Dos 407 isolados, identificou-se 55 espécies bacterianas pertencentes a 11 famílias distintas. A família Enterobacteriaceae foi a que predominou dentre as densidades avaliadas, seguida da alcaligenaceae. A densidade de estocagem 4 peixes/m2 apresentou diferenças estatísticas significativa, com menor freqüência de famílias. Observou-se elevado número de bactérias resistentes principalmente à ampicilina e eritromicina, enquanto que menos de 15% dos isolados foram resistentes a gentamicina e cloranfenicol. Dentre os isolados analisados, 96% apresentaram índice de múltipla resistência a antimicrobianos (MAR) maior ou igual a 0,2. A intensificação dos sistemas promoveu o aumento da concentração bacterias, sem relação com as variáveis físicas e químicas, foi identificado uma diversidade de espécies bacterianas e houve alto índice de resistência e multirresistência aos antimicrobianos testados.
43
Millman, Caroline Elizabeth. "Perceptions and risks : food-borne pathogens in the domestic environment." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/perceptions-and-risks-foodborne-pathogens-in-the-domestic-environment(daae2641-ddf5-41d0-877c-1ba1533ad243).html.
Full textAbstract:
Food-borne illness is a significant burden both with regard to public health and financially. Efforts to reduce the level of food-borne illness continue to concentrate on the full food supply chain with particular regard given to Campylobacter, the most commonly reported zoonosis and the greatest burden to public health. The focus of this research is domestic food safety practises, where there is no regulation. Food safety is reliant on people’s knowledge or awareness, their ability to adopt safe food handling practises and for the correct behaviours to achieve this, to be routine. The elicitation of awareness and perceptions with regard to food safety are problematic due to the complexities of human nature, including the presence of several forms of bias, such as social desirability bias and optimistic bias. The research was designed in order to try to minimise such biases, whilst further understanding influences on food safety preparation behaviour. Food safety preparation behaviours and kitchen hygiene were investigated between people who had campylobacteriosis in comparison to people who had not had food poisoning. Whilst no difference was noted in the kitchen hygiene between the two groups, significant differences were noted in self-reported food preparation behaviours. Optimistic bias was exhibited by both groups but when tested again after six months had elapsed, the group who had not had food poisoning increased their optimism, introducing a significant difference in optimistic bias between the two groups. Awareness of a number of unsafe food behaviours was explored for individuals and groups of people using a method developed as part of the research. This method of hazard awareness uses video as a stimulus, creating an interactive survey, combined with attitudinal and demographic data. Changes were made to perceptions of knowledge and risk following the hazard perception challenge, with the number of hazards missed, influencing this movement in perception. The risk perception of unsafe food handling behaviours was examined using a novel technique Best-Worst Scaling, in order to identify relative risks. This technique, in conjunction with latent class modelling, demonstrated a difference in perceptions between food safety experts and members of the general public. However, these differences are nuanced and demonstrate that heterogeneity exists both within and across the groups. Taken together, these findings have extended the research on domestic food safety behaviour and risk perceptions. It has done so by developing and testing novel methods to elicit relative risk perceptions and hazard perception with regard to food safety behaviours. The results provide valuable evidence for stakeholders particularly with regard to the novel methods used in identifying the heterogeneity and influences of food safety behaviour between groups of people. It also provides important tools for stakeholders, risk managers and communicators to use in future research, communication and education.
44
Williams, David Lee. "Assessment of the Survival of Microbial Pathogens in the Environment." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/223315.
Full textAbstract:
The studies presented here evaluate the survival of different types of pathogens in a variety of environments. The study Appendix A focuses on the presence of enteric bacteria in reusable shopping bags. We demonstrated that ninety-seven percent of individuals surveyed never washed their reusable shopping bags and that this lack of washing can lead to the buildup of potentially harmful bacteria such as Salmonella spp. The hand-washing of the bags was shown to reduce seeded organisms to below detectable limits. Appendix B examines the survival of Bacillus altrophaeus endospores during household laundering. It was demonstrated that detergent alone didn't significantly reduce the number of viable endospores or their spread to other garments and that bleach is necessary to significantly reduce the number of viable endospores and their spread. Risks for infection were significantly lower when bleach was used during laundering. Appendix C details the survival of Ascaris ova in biosolid-amended Brazito sandy loam and clay loam. Survival of Ascaris ova was significantly higher in clay soil and ova inactivation increased with increasing temperature. The risk for Ascaris infection from consuming raw lettuce grown on such soils was calculated and it was found that annual risks for infection decreased significantly with time after harvest.
45
Leewattanapasuk, Worraanong. "Environmental sensing in the fungal pathogen of humans candida glabrata." Thesis, University of Kent, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534325.
Full text
46
Prattley, Deborah Jayne. "Risk-based suveillance in animal health : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1011.
Full textAbstract:
Animal health surveillance is an important part of animal health care, particularly in countries dependent on livestock for food production and international trade. There are two major issues related to the provision of e®ective surveillance activities. Firstly, for good information to become available, the design and conduct of data collection activ- ities should be carried out following sound statistical principles. In reality, constraints such as imperfect tests and unavoidably-biased sampling strategies hinder straightfor- ward analysis and interpretation of survey results. Risk-based surveillance is used to target high-risk sub-populations to increase e±ciency of disease detection; however, biased datasets are generated. This thesis develops methodologies to design risk-based surveillance systems and al- low statistically valid analysis of the inherently biased data they generate. The ¯rst example describes the development of a method to analyse surveillance data gathered for bovine spongiform encephalopathy (BSE). The data are collected from four dif- ferent surveillance streams of animals tested for BSE, with each stream containing unavoidable biases and limitations. In the BSurvE model, these data are combined with demographic information for each birth cohort to estimate the proportion of each birth cohort infected with BSE. The prevalence of BSE in a national herd can then be estimated using the method of moments, whereby the observed number of infected animals is equated with the expected number. The upper 95% con¯dence limit for the prevalence is estimated both for infected countries and for those where no BSE has previously been detected. A similar approach to that used in BSurvE is then applied to surveillance data for trichinellosis, for which risk-based post-mortem testing is also performed. Negative results from multiple species using di®erent, imperfect tests are combined to give an estimate of the upper 95% con¯dence limit of the national prevalence of trichinellosis in a reference population. This method is used to provide support for freedom from trichinellosis in Great Britain. A di®erent approach to risk-based surveillance is explored as the surveillance strategy for detection of exotic causes of abortion in sheep and goats in New Zealand is examined. Using a geographic information system (GIS) maps of disease risk factors were overlain to produce a risk landscape for the lower North Island. This was used to demonstrate how areas of high- and low-risk of disease occurrence can be identi¯ed and used to guide the design of a risk-based surveillance programme. Secondly, within one surveillance objective there may be many ways in which the available funds or human resources could be distributed. This thesis develops a method to assess BSE surveillance programmes, and provides tools to facilitate BSE detection on the basis of infection risk and to increase the e±ciency of surveillance strategies. A novel approach to allocation of resources is developed, where portfolio theory con- cepts from ¯nance are applied to animal health surveillance. The example of surveil- lance for exotic causes of sheep and goat abortion is expanded upon. Risk of disease occurrence is assessed for a population over di®erent time periods and geographical areas within a country, and portfolio theory used to allocate the number of tests to be carried out within each of these boundaries. This method is shown to be more likely to detect disease in a population when compared to proportional allocation of the available resources. The studies presented here show new approaches that allow better utilisation of imperfect data and more e±cient use of available resources. They allow development of surveillance programmes containing an appropriate balance of scanning and targeted surveillance activities. Application of these methods will enhance the implementation and value of surveillance in animal health.
47
Deere, Daniel Alun. "Survival and distribution of Aeromonas salmonicida in aquatic environments." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283475.
Full text
48
Ferguson, Yvonne. "Survival strategies of Aeromonas salmonicida in aquatic environments." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294445.
Full textAbstract:
A luminescence-based detection system was developed to study changes in the survival and activity of cells following release from moribund and dead fish. A.salmonicida was chromosomally marked with the genes encoding bacterial luciferase, originally isolated from Vibrio harveyi. Characterisation of the growth and luminescence of the lux-marked strain demonstrated that light was directly proportional to cell biomass concentration during logarithmic growth. The survival of lux-marked and wild type A.salmonicida strains was investigated in sterile sea water at 4°C. The number of culturable cells declined rapidly, but the total number of cells remained relatively constant, suggesting A. salmonicida entered a nonculturable state. The survival of lux-marked A. salmonicida did not significantly differ from that of the wild type strain. A small number of cells remained culturable throughout starvation experiments and luminometry confirmed that the lux-marked cells were metabolically active, possibly surviving by cryptic growth. The viability of putative dormant cells could not be established since these cells could not be reactivated following the addition of a range of substrates. The lux-marked A.salmonicida strain was pathogenic only when injected at high doses. This poor virulence was probably due to loss of the proteinaceous A-layer which is responsible for hydrophobic cell interactions and cell defence against lytic agents. This prevented further studies aimed at determining the virulence of nonculturable cells using this strain. Preliminary experiments indicated the potential of the lux-marked system for studying vertical transmission of A. salmonicida. The main sites for attachment of the lux-marked strain were the gill and skin/mucus regions. Identical results were obtained using a wild type virulent A. salmonicida strain, but significantly higher numbers of cells were recovered from fish tissue.
49
Blanford, William James. "Characterization and remediation of pathogen, solvent, and petroleum contaminated aquifers." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279841.
Full textAbstract:
This work contains the results of studies of three fluid projects that investigated aspects of groundwater contaminant transport and remediation. The first project performed at Hill Air Force Base in Utah evaluated the performance of a vertical water flushing system for the remediation of a multi-component non-aqueous phase liquid. This project also encompassed determining contaminant distribution through soil core analysis and partitioning tracer studies. The work determined that the limited aqueous solubility of the primary contaminants led to the lack of efficient removal by the vertical water flushing system. The second remediation test evaluated the performance of the solubility enhancing agent cyclodextrin in restoring the contaminated aquifer at Air Force Plant 44 in Tucson, Arizona. The results concluded that this advanced remediation technique was efficient in removing trichloroethene. Further, the project demonstrated the ability to separate TCE from the extracted solution through treatment with an air-stripping system and re-inject it for another multiple flushing of the aquifer. Additional site assessment including determination of lithological and contaminant distribution through well-bore sampling and system optimization by conducting a series of vertical tracer studies. To evaluate the impact of groundwater chemistry and travel distances on the transport behavior of enteric virus, experiments were conducted in the unconfined aquifer at the USGS Cape Cod Research Site. Separate experiments examined the transport behavior of bromide (Br-) and the bacteriophage PRD-1 in the effluent plume and the shallower uncontaminated groundwater. Results indicated the vast majority of the bacteriophages were lost from solution upon injection. The results further showed that this initial loss occurred within the first meter for the uncontaminated zone, whereas it occurred over a 4-meter distance in the contaminated zone. The greater distance required for the contaminated zone to defect similar mass loss is attributed to anion-exchange competition by organic matter, phosphate, and other anions present in higher concentrations in the contaminated zone. The results of this study indicate that a small, but infectious fraction of viable virus particles can persist and travel significant distances in sedimentary aquifers, despite variability in water chemistry.
50
Kassem, Issmat I. "Detection and Characterization of Staphylococcal Pathogens in the Environment: A Community Approach." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1241717899.
Full textAbstract:
Dissertation (Ph.D.)--University of Toledo, 2009.Typescript. "Submitted in partial fulfillment of the requirements for The Doctor of Philosophy in Biology (Ecology-Track)." Bibliography: leaves 108-126.