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Littérature scientifique sur le sujet « Environmental pathogens »

Auteur : Grafiati

Publié le 22 juin 2023

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Articles de revues sur le sujet "Environmental pathogens"

Quinlan, Robert J. « Human parental effort and environmental risk ». Proceedings of the Royal Society B : Biological Sciences 274, n^o 1606 (18 octobre 2006) : 121–25. http://dx.doi.org/10.1098/rspb.2006.3690.

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Parental investment decisions depend on multiple factors, including the extent that parental care benefits offspring. Humans should show reduced parental effort in environments where parenting cannot improve offspring survival. Data from the standard cross-cultural sample are used to test this prediction. The results show that maternal care was inversely associated with famine and warfare, and also showed a quadratic association with pathogen stress, increasing as pathogen stress increased to moderate levels, but decreasing at higher levels. Age at weaning showed a similar quadratic relation with pathogens. The curvilinear associations between parental effort and pathogen stress may reflect that the saturation point of parental care is a function of environmental hazards. Paternal involvement was also inversely related to pathogen stress. The association between pathogens and paternal involvement was partially mediated by polygyny. In sum, maternal and paternal care appears to have somewhat different relations with environmental hazards, presumably owing to sex-specific tradeoffs in reproductive effort.

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Lanzas, Cristina, Kale Davies, Samantha Erwin et Daniel Dawson. « On modelling environmentally transmitted pathogens ». Interface Focus 10, n^o 1 (13 décembre 2019) : 20190056. http://dx.doi.org/10.1098/rsfs.2019.0056.

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Many pathogens are able to replicate or survive in abiotic environments. Disease transmission models that include environmental reservoirs and environment-to-host transmission have used a variety of functional forms and modelling frameworks without a clear connection to pathogen ecology or space and time scales. We present a conceptual framework to organize microparasites based on the role that abiotic environments play in their lifecycle. Mean-field and individual-based models for environmental transmission are analysed and compared. We show considerable divergence between both modelling approaches when conditions do not facilitate well mixing and for pathogens with fast dynamics in the environment. We conclude with recommendations for modelling environmentally transmitted pathogens based on the pathogen lifecycle and time and spatial scales of the host–pathogen system under consideration.

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Anttila, Jani, Jouni Laakso, Veijo Kaitala et Lasse Ruokolainen. « Environmental variation enables invasions of environmental opportunist pathogens ». Oikos 125, n^o 8 (27 novembre 2015) : 1144–52. http://dx.doi.org/10.1111/oik.02913.

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Leach, Clinton B., Colleen T. Webb et Paul C. Cross. « When environmentally persistent pathogens transform good habitat into ecological traps ». Royal Society Open Science 3, n^o 3 (mars 2016) : 160051. http://dx.doi.org/10.1098/rsos.160051.

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Habitat quality plays an important role in the dynamics and stability of wildlife metapopulations. However, the benefits of high-quality habitat may be modulated by the presence of an environmentally persistent pathogen. In some cases, the presence of environmental pathogen reservoirs on high-quality habitat may lead to the creation of ecological traps, wherein host individuals preferentially colonize high-quality habitat, but are then exposed to increased infection risk and disease-induced mortality. We explored this possibility through the development of a stochastic patch occupancy model, where we varied the pathogen’s virulence, transmission rate and environmental persistence as well as the distribution of habitat quality in the host metapopulation. This model suggests that for pathogens with intermediate levels of spread, high-quality habitat can serve as an ecological trap, and can be detrimental to host persistence relative to low-quality habitat. This inversion of the relative roles of high- and low-quality habitat highlights the importance of considering the interaction between spatial structure and pathogen transmission when managing wildlife populations exposed to an environmentally persistent pathogen.

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Pedersen, Joel A., Katherine D. McMahon et Craig H. Benson. « Prions : Novel Pathogens of Environmental Concern ? » Journal of Environmental Engineering 132, n^o 9 (septembre 2006) : 967–69. http://dx.doi.org/10.1061/(asce)0733-9372(2006)132:9(967).

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Rysanek, Dusan, Monika Zouharova et Vladimir Babak. « Monitoring major mastitis pathogens at the population level based on examination of bulk tank milk samples ». Journal of Dairy Research 76, n^o 1 (5 janvier 2009) : 117–23. http://dx.doi.org/10.1017/s0022029908003816.

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The objective was to determine the proportions and bacterial counts of major mastitis pathogens in samples of bulk tank milk (BTM), as well as to clarify the relationship between these bacteria counts and bulk tank somatic cell count (BTSCC). The purpose was to judge the importance of the counts of mammary pathogens for BTSCC at the population level. Samples of BTM were collected from 268 randomly selected anonymous dairy herds (with approximately 29 000 dairy cows). Staphylococcus aureus, other coagulase-positive staphylococci, Streptococcus agalactiae and Streptococcus dysgalactiae were grouped as contagious pathogens, and Streptococcus uberis, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Enterococcus faecium as environmental pathogens. Based on assessment of the dominant pathogen in each herd, environmental pathogens were found to dominate. Counts of specific mammary pathogens in BTM samples did not exceed a geometric mean of 1000 cfu/ml. Significant differences were documented in BTSCC between BTM samples containing Str. agalactiae, Staph. aureus, and Str. dysgalactiae and BTM samples that were pathogen-free. Geometric means of BTSCC associated with these pathogens were noticeably higher than the overall BTSCC (Str. agalactiae 243 628; Staph. aureus 205 610; Str. dysgalactiae 203 978; overall 173 000 cells/ml). It follows that the somatic cell count (SCC) associated with these pathogens contributed substantially to the overall BTSCC. Environmental pathogens predominated in samples of BTM with SCC <300×103/ml and contagious mastitis pathogens predominated in BTM samples with SCC >300×103/ml. No correlation was detected between bacterial counts of specific pathogens and BTSCC. This study revealed that the assessment of bacterial counts of mammary pathogens in samples of BTM in relation to BTSCC is applicable for the monitoring of changes in the occurrence of major mastitis pathogens in dairy herds at a national level.

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Shea, Dylan, Andrew Bateman, Shaorong Li, Amy Tabata, Angela Schulze, Gideon Mordecai, Lindsey Ogston et al. « Environmental DNA from multiple pathogens is elevated near active Atlantic salmon farms ». Proceedings of the Royal Society B : Biological Sciences 287, n^o 1937 (21 octobre 2020) : 20202010. http://dx.doi.org/10.1098/rspb.2020.2010.

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The spread of infection from reservoir host populations is a key mechanism for disease emergence and extinction risk and is a management concern for salmon aquaculture and fisheries. Using a quantitative environmental DNA methodology, we assessed pathogen environmental DNA in relation to salmon farms in coastal British Columbia, Canada, by testing for 39 species of salmon pathogens (viral, bacterial, and eukaryotic) in 134 marine environmental samples at 58 salmon farm sites (both active and inactive) over 3 years. Environmental DNA from 22 pathogen species was detected 496 times and species varied in their occurrence among years and sites, likely reflecting variation in environmental factors, other native host species, and strength of association with domesticated Atlantic salmon. Overall, we found that the probability of detecting pathogen environmental DNA (eDNA) was 2.72 (95% CI: 1.48, 5.02) times higher at active versus inactive salmon farm sites and 1.76 (95% CI: 1.28, 2.42) times higher per standard deviation increase in domesticated Atlantic salmon eDNA concentration at a site. If the distribution of pathogen eDNA accurately reflects the distribution of viable pathogens, our findings suggest that salmon farms serve as a potential reservoir for a number of infectious agents; thereby elevating the risk of exposure for wild salmon and other fish species that share the marine environment.

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Ao, Dong, Yue Huang, Tao Xue, Nan Wang et Rong Chen. « Implication of environmental factors on the occurrence of pathogens in urban landscape ponds with reclaimed wastewater replenishment ». Blue-Green Systems 1, n^o 1 (1 janvier 2019) : 119–33. http://dx.doi.org/10.2166/bgs.2019.916.

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Abstract One year of continuous observation of bacterial and viral pathogen concentrations in overlying water and sediment of three urban landscape ponds replenished with reclaimed wastewater (RW) ponds was carried out to establish the distribution of pathogens and investigate the effects of environmental factors on that in RW ponds. The pathogens were represented by Escherichia coli and three common viral pathogens (enterovirus, norovirus, and rotavirus). Results indicated that the peak concentrations of pathogens occur from August to October. Pathogens present in sediment should be paid much more attention than those in overlying water, as they mainly contribute to the favorable conditions for survival and regrowth of pathogens in sediments. Cluster and redundancy analyses revealed that the environmental factors of chlorophyll a (Chl-a), organic matter, and water transparency have key impacts on the occurrence of pathogens. This infers that the practical way to reduce pathogenic risks in RW ponds is to control the algae bloom and improve the transparency of water bodies. Furthermore, based on breakpoint regression analyses, the appropriate ranges of Chl-a and transparency are suggested to be less than 57 mg/m3 and greater than 68 cm, respectively, to reduce the concentration of pathogens in urban landscape ponds replenished with RW.

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Hua, Megan, William Huang, Albert Chen, Michael Rehmet, Cade Jin et Zuyi Huang. « Comparison of Antimicrobial Resistance Detected in Environmental and Clinical Isolates from Historical Data for the US ». BioMed Research International 2020 (13 avril 2020) : 1–11. http://dx.doi.org/10.1155/2020/4254530.

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Antimicrobial resistance (AMR) has become an urgent public health issue, as pathogens are becoming increasingly resistant to commonly used antimicrobials. While AMR isolate data are available in the NCBI Pathogen Detection Isolates Browser (NPDIB) database, few researches have been performed to compare antimicrobial resistance detected in environmental and clinical isolates. To address this, this work conducted the first multivariate statistical analysis of antimicrobial-resistance pathogens detected in NPDIB clinical and environmental isolates for the US from 2013 to 2018. The highly occurring AMR genes and pathogens were identified for both clinical and environmental settings, and the historical profiles of those genes and pathogens were then compared for the two settings. It was found that Salmonella enterica and E. coli and Shigella were the highly occurring AMR pathogens for both settings. Additionally, the genes fosA, oqxB, ble, floR, fosA7, mcr-9.1, aadA1, aadA2, ant(2”)-Ia, aph(3”)-Ib, aph(3’)-Ia, aph(6)-Id, blaTEM-1, qacEdelta1, sul1, sul2, tet(A), and tet(B) were mostly detected for both clinical and environmental settings. Ampicillin, ceftriaxone, gentamicin, tetracycline, and cefoxitin were the antimicrobials which got the most resistance in both settings. The historical profiles of these genes, pathogens, and antimicrobials indicated that higher occurrence frequencies generally took place earlier in the environmental setting than in the clinical setting.

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Miller, S. E., et D. N. Howell. « Extreme Pathogens ». Microscopy and Microanalysis 6, S2 (août 2000) : 638–39. http://dx.doi.org/10.1017/s1431927600035686.

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Organisms are generally designated as “extreme” when they possess adaptations that allow them to flourish when one or more environmental parameters (e.g., temperature, ionizing radiation, oxygen, water, nutrients, inorganic ions) are at unusually high or low levels. A trade-off for this extraordinary resilience is that such organisms often grow poorly (if at all) in more conventional milieus. As a result, few of them are mammalian pathogens. (Anaerobic bacteria, which frequently thrive in the hypoxic conditions afforded by devitalized tissue, are an exception to this rule.)A broader definition of “extremity” encompasses all organisms that occupy narrow or unusual environmental niches. In this more inclusive scheme, a wealth of viruses, bacteria, fungi, and parasites with pathogenic potential in humans can be considered extreme. These organisms often pose formidable diagnostic challenges. Many have extremely narrow host ranges, rendering passage in animals and development of model systems for infection difficult or impossible.

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Thèses sur le sujet "Environmental pathogens"

Karim, Mohammad Rezaul. « Survival of indicator microorganisms and enteric pathogens in wetlands ». Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284066.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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)

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Sexton, Jonathan D. « The Occurrence and Control of Pathogens on Fomites ». Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/312769.

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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.

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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.

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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.

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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.

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Dulaney, D. R., Kurt J. Maier et Phillip R. Scheuerman. « Data Requirements for Developing Effective Pathogen TMDLs ». Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etsu-works/2938.

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Manning, C. A., Kimberlee K. Hall, Brian G. Evanshen, Kurt J. Maier et 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.

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Livres sur le sujet "Environmental pathogens"

Bowman, Dwight D. Manure pathogens : Manure management, regulations, and water quality protection. Alexandria, Va : WEF Press, 2009.

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Bowman, Dwight D. Manure pathogens : Manure management, regulations, and water quality protection. Alexandria, Va : WEF Press, 2009.

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Schaible, Ulrich E., et Haas Albert. Intracellular niches of microbes : A pathogens guide through the host cell. Weinheim : Wiley-VCH, 2009.

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United States. Environmental Protection Agency. Office of Research and Development. et United States. Environmental Protection Agency. Office of Water., dir. EPA action plan for beaches and recreational waters : Reducing exposures to waterborne pathogens. Washington, DC : Office of Research and Development and Office of Water, U.S. Environmental Protection Agency, 1999.

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B, Rose Joan, et Dreelin Erin A, dir. Effective cross-border monitoring systems for waterborne microbial pathogens : A plan for action. London : IWA Pub., 2008.

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M, Lund Barbara, et Society for Applied Bacteriology, dir. Enterobacteriaceae in the environment and as pathogens : Proceedings of a symposium held at the University of Nottingham 7-9 July 1987. Oxford [England] : Blackwell Scientific, 1988.

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United States. Environmental Protection Agency. Office of Research and Development., dir. Environmental regulations and technology : Control of pathogens and vector attraction in sewage sludge (including domestic septage) under 40 CFR part 503. Washington, DC : U.S. Environmental Protection Agency, Office of Research and Development, 1992.

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1951-, Austin B., dir. Pathogens in the environment. Oxford : Blackwell Scientific Publications, 1991.

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M, Lund Barbara, dir. Enterobacteriaceae in the environment and as pathogens. Oxford : Blackwell Scientific, 1988.

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D, Sartory, et Society for Applied Microbiology, dir. Pathogens in the environment and changing ecosystems. Oxford, UK : Published for the Society for Applied Microbiology by Blackwell Science, 2003.

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Chapitres de livres sur le sujet "Environmental pathogens"

Siegl, Alexander, et Matthias Horn. « Lessons from Environmental Chlamydiae ». Dans Intracellular Pathogens I, 51–73. Washington, DC, USA : ASM Press, 2014. http://dx.doi.org/10.1128/9781555817329.ch3.

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Burkholder, Kristin M., et Mary X. D. O’Riordan. « Opportunisitic Pathogens of Humans ». Dans Advances in Environmental Microbiology, 301–57. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-28170-4_11.

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Levetin, Estelle. « Aerobiology of Agricultural Pathogens ». Dans Manual of Environmental Microbiology, 3.2.8–1–3.2.8–20. Washington, DC, USA : ASM Press, 2015. http://dx.doi.org/10.1128/9781555818821.ch3.2.8.

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Blanch, Anicet R., et Juan Jofre. « Emerging Pathogens in Wastewaters ». Dans The Handbook of Environmental Chemistry, 141–63. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b97178.

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Hackney, Cameron R., et Morris E. Potter. « Human-Associated Bacterial Pathogens ». Dans Environmental Indicators and Shellfish Safety, 154–71. Boston, MA : Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2035-1_4.

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Venkitanarayanan, Kumar, Abhinav Upadhyay, Meera Surendran Nair et Indu Upadhyaya. « The Effects of Environmental Conditions and External Treatments on Virulence of Foodborne Pathogens ». Dans Foodborne Pathogens, 305–32. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56836-2_10.

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Ford, Tim, et Steve Hamner. « Control of Waterborne Pathogens in Developing Countries ». Dans Environmental Microbiology, 33–56. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2010. http://dx.doi.org/10.1002/9780470495117.ch2.

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Medema, Gertjan. « Microbial Risk Assessment of Pathogens in Water ». Dans Environmental Toxicology, 361–401. New York, NY : Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-5764-0_14.

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Boehm, Alexandria B., et Jeffrey A. Soller. « Recreational Water Risk : Pathogens and Fecal Indicators ». Dans Environmental Toxicology, 441–59. New York, NY : Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-5764-0_16.

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Derome, Nicolas, Jeff Gauthier, Sébastien Boutin et Martin Llewellyn. « Bacterial Opportunistic Pathogens of Fish ». Dans Advances in Environmental Microbiology, 81–108. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-28170-4_4.

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Actes de conférences sur le sujet "Environmental pathogens"

Juneja, Vijay K. « Intervention strategies for control of foodborne pathogens ». Dans Optical Technologies for Industrial, Environmental, and Biological Sensing, sous la direction de Bent S. Bennedsen, Yud-Ren Chen, George E. Meyer, Andre G. Senecal et Shu-I. Tu. SPIE, 2004. http://dx.doi.org/10.1117/12.530119.

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Singh, Ashutosh, Rakesh K. Singh et Arun K. Bhunia. « Light-emission-based biosensor for detection of food pathogens : a review ». Dans Environmental and Industrial Sensing, sous la direction de Yud-Ren Chen et Shu-I. Tu. SPIE, 2001. http://dx.doi.org/10.1117/12.418723.

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Andreotti, Peter E., Richard Meyer, Thomas Campbell, Michael T. Goode, Deborah L. Menking, Emily D. Myers, Tom Palenius et Larry H. Stanker. « Detection and identification of animal and food pathogens using time-resolved fluorescence ». Dans Environmental and Industrial Sensing, sous la direction de Yud-Ren Chen et Shu-I. Tu. SPIE, 2001. http://dx.doi.org/10.1117/12.418741.

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Kuwahara, S., J. Cuello, K. Reynolds et C. Gerba. « Synergistic UV-Ozone Effects on the Treatment of Pathogens in Secondary Effluent ». Dans International Conference On Environmental Systems. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2003. http://dx.doi.org/10.4271/2003-01-2563.

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Kobayashi, Takako, Wataru Miyazaki, Kazukiyo Yamamoto, Yuji Miura et Takeo Kondo. « A Conceptual Design on the BSL-4 Location and Management ». Dans ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49512.

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In the event of an outbreak of an infectious disease, the pathogen of which is highly contagious, or when there are patients suspected to be infected with such a pathogen, it is essential to start treating the patients and controlling infection immediately. As the transportation system has been well developed, there are more worries about terrorist attacks using biological agents now than ever before. It is a real possibility that even the most dangerous pathogens that are the causes of Class 1 infectious diseases specified in the Infectious Diseases Act, such as hemorrhagic fever or smallpox, be brought into Japan. Those most dangerous pathogens can be dealt with only by special laboratories that satisfy BSL-4 (Bio-Safety Level 4) specified by WHO (BSL-4 laboratories)(1). As there are no BSL-4 laboratories in operation in Japan at present, it is an immediate requirement to develop a suitable environment for the operation of laboratories of this kind, in order to maintain effective health risk management for the Japanese people. In this research, in order to put BSL-4 laboratories in operation in Japan, we will clarify what relevant environmental factors are in different types of possible locations. Based on that, we will propose to utilize those laboratories not only in emergencies, but also in normal times. We will also discuss the necessary conditions in the social environment of contemporary Japan for BSL-4 laboratories’ operation.

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Smith, Jr., James E., et Robert B. Brobst. « Changing Approaches to Controlling Pathogens in Biosolids and Their Vector Attractiveness ». Dans World Water and Environmental Resources Congress 2001. Reston, VA : American Society of Civil Engineers, 2001. http://dx.doi.org/10.1061/40569(2001)290.

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Patterson, Craig, Rajib Sinha, John Heckman, Richa Pugalia, Alpana Divekar, Prakhar Gupta et Skand Saksena. « Evaluation of Household Drinking Water Treatment Systems for Removal of Pathogens ». Dans World Environmental and Water Resources Congress 2022. Reston, VA : American Society of Civil Engineers, 2022. http://dx.doi.org/10.1061/9780784484258.003.

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Ozen, Aysu, Kacey Montgomery, Pat Jegier, Stacey Patterson, Kathleen A. Daumer, Steven A. Ripp, Jay L. Garland et Gary S. Sayler. « Development of bacteriophage-based bioluminescent bioreporters for monitoring of microbial pathogens ». Dans Optical Technologies for Industrial, Environmental, and Biological Sensing, sous la direction de Tuan Vo-Dinh, Guenter Gauglitz, Robert A. Lieberman, Klaus P. Schaefer et Dennis K. Killinger. SPIE, 2004. http://dx.doi.org/10.1117/12.516181.

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Struck, Scott D., Michael Borst et Ariamalar Selvakumar. « The Role of Stormwater Research in BMP Design — Pathogens and Regulatory Demands ». Dans World Water and Environmental Resources Congress 2005. Reston, VA : American Society of Civil Engineers, 2005. http://dx.doi.org/10.1061/40792(173)220.

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Luster-Teasley, Stephanie, Christopher Jackson et Chanel Rogers. « Inactivation of Pathogens in Agricultural Wastewater Using Controlled Release Chemical Oxidation Polymer System ». Dans World Environmental and Water Resources Congress 2011. Reston, VA : American Society of Civil Engineers, 2011. http://dx.doi.org/10.1061/41173(414)163.

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Rapports d'organisations sur le sujet "Environmental pathogens"

Prusky, Dov, et Jeffrey Rollins. Modulation of pathogenicity of postharvest pathogens by environmental pH. United States Department of Agriculture, décembre 2006. http://dx.doi.org/10.32747/2006.7587237.bard.

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Until recently, environmental pH was not considered a factor in determining pathogen compatibility. Our hypothesis was that the environmental pH at the infection site, which is dynamically controlled by activities of both the host and the pathogen, regulates the expression of genes necessary for disease development in Colletotrichum gloeosporioides and Sclerotinia sclerotiorum. This form of regulation ensures that genes are expressed at optimal conditions for their encoded activities.Pectate lyase encoded by pelB, has been demonstrated to play a key role in virulence of C. gloeosporioides in avocado fruit. Polyglacturonase synergism with oxalic acid production is considered to be an essential pathogenicity determinant in the interactions of S. sclerotiorum with its numerous hosts. A common regulatory feature of these virulence and pathogenicity factors is their dependence upon environmental pH conditions within the host niche to create optimal conditions for expression and secretion. In this proposal we have examined, 1) the mechanisms employed by these fungi to establish a suitable pH environment, 2) the molecular levels at which genes and gene products are regulated in response to environmental pH, and 3) the molecular basis and functional importance of pH-responsive gene regulation during pathogenicity. The specific objectives of the proposal were: 1. Characterize the mechanism of local pH modulation and the effect of ambient pH on the expression and secretion of virulence factors. 2. Provide evidence that a conserved molecular pathway for pH-responsive gene expression exists in C. gloeosporioides by cloning a pacC gene homologue. 3. Determine the role of pacC in pathogenicity by gene disruption and activating mutations. Major conclusions 1. We determined the importance of nitrogen source and external pH in the secretion of the virulence factor pectate lyase with respect to the ambient pH transcriptional regulator pacC. It was concluded that nitrogen source availability and ambient pH are two independent signals for the transcriptional regulation of genes required for the disease process of C. gloeosporioides and possibly of other pathogens. 2. We also determined that availability of ammonia regulate independently the alkalinization process and pelB expression, pecate lyase secretion and virulence of C. gloeosporioides. 3. Gene disruption of pacC reduced virulence of C. gloeosporioides however did not reduced fully pelB expression. It was concluded that pelB expression is regulated by several factors including pH, nitrogen and carbon sources. 4. Gene disruption of pacC reduced virulence of S. slcerotiourum Creation of a dominant activating

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Prusky, Dov, Lisa Vaillancourt et Robert Fluhr. Host Ammonification by Postharvest Pathogens and its Contribution to Fungal Colonization and Symptom Development. United States Department of Agriculture, décembre 2006. http://dx.doi.org/10.32747/2006.7592640.bard.

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Postharvest decay of fruits and vegetables caused by pathogenic and saprophytic fungi significantly impairs the quality and quantity of fresh produce brought to market. Consequently, there is considerable interest in identifying factors that determine the susceptibility of these commodities to pathogen infection. Insidious postharvest decays remain quiescent during fruit growth and harvest, but activate during the postharvest period. A key response to the physiological changes occurring during fruit ripening is the initiation of ammonium secretion by the pathogen. Ammonium ions at the infection site (ammonification) have subsequent effects on both the pathogen and the host. An accompanying alkalinization process resulting from ammonia accumulation contributes to pathogenicity, since some important fungal virulence factors, (such as pectate lyase in Colletotrichum sp.), are significantly expressed only under alkaline conditions. In this proposal, investigated the mechanisms by which ammonification and alkalinization of infected tissues by the pathogen affect the host’s defense response to fungal attack, and instead increase compatibility during postharvest pathogen-host interactions. Our hypotheses were:1) that host signals, including ripening-related changes, induce secretion of ammonia by the pathogen; 2) that ammonia accumulation, and the resultant environmental alkalinization regulate the expression of fungal virulence genes that are essential for postharvest rot development; 3) that ammonification enhanced fungal colonization, by “suppression of host responses”, including production of reactive oxygen species, activation of superoxide, and polyphenol oxidase production. Our objectives were: to analyze: 1) factor(s) which activate the production and secretion of ammonia by the fungus; 2) fungal gene(s) that play role(s) in the ammonification process; 3) the relationship between ammonification and the activation of host defense response(s) during pathogen colonization; and 4) analyze hostgene expression in alkalinized regions of fruits attacked by hemibiotrophic fungi.

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Oron, Gideon, Raphi Mandelbaum, Carlos E. Enriquez, Robert Armon, Yoseph Manor, L. Gillerman, A. Alum et Charles P. Gerba. Optimization of Secondary Wastewater Reuse to Minimize Environmental Risks. United States Department of Agriculture, décembre 1999. http://dx.doi.org/10.32747/1999.7573077.bard.

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The main purpose of the research was to examine approaches and to evaluate methods for minimizing the risks during applying treated domestic wastewater for agricultural irrigation. This general purpose consisted of examining under field conditions the possibilities when implementing different application technologies for minimizing health and environmental risks. It was assumed that Subsurface Drip Irrigation (SDI) will provide adequate conditions for safe effluent reuse. Controlled field experiments where conducted in commercial fields to evaluate the alternatives. Main efforts where conducted in Israel in the grape vineyard in Arad heights, in the field crops in Kibbutz Chafets Chaim and in Arizona in fields adjacent to the University campus. The complementary part was to examine the behavior of the various pathogens in the effluent-soil-plant system. The analysis is based on controlled experiments, primarily in greenhouse along with field experiments. Molecular biology methods were used to identify the behavior of the pathogens in the components of the system. The project included as well examining the effluent quality in various sites, primarily those in which treated wastewater is reused for agricultural irrigation. The monitoring included conventional parameters however, also parasites such as Giardia and Cryptosporidium. The results obtained indicate the prominent advantages of using Subsurface Drip Irrigation (SDI) method for minimizing health and environmental risks during application of secondary effluent. A theoretical model for assessing the risks while applying treated wastewater was completed as well. The management model shows the risks during various scenarios of wastewater quality, application technology and related human exposure.

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Freeman, Stanley, Russell Rodriguez, Adel Al-Abed, Roni Cohen, David Ezra et Regina Redman. Use of fungal endophytes to increase cucurbit plant performance by conferring abiotic and biotic stress tolerance. United States Department of Agriculture, janvier 2014. http://dx.doi.org/10.32747/2014.7613893.bard.

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Major threats to agricultural sustainability in the 21st century are drought, increasing temperatures, soil salinity and soilborne pathogens, all of which are being exacerbated by climate change and pesticide abolition and are burning issues related to agriculture in the Middle East. We have found that Class 2 fungal endophytes adapt native plants to environmental stresses (drought, heat and salt) in a habitat-specific manner, and that these endophytes can confer stress tolerance to genetically distant monocot and eudicot hosts. In the past, we generated a uv non-pathogenic endophytic mutant of Colletotrichum magna (path-1) that colonized cucurbits, induced drought tolerance and enhanced growth, and protected 85% - 100% against disease caused by certain pathogenic fungi. We propose: 1) utilizing path-1 and additional endophtyic microorganisms to be isolated from stress-tolerant local, wild cucurbit watermelon, Citrulluscolocynthis, growing in the Dead Sea and Arava desert areas, 2) generate abiotic and biotic tolerant melon crop plants, colonized by the isolated endophytes, to increase crop yields under extreme environmental conditions such as salinity, heat and drought stress, 3) manage soilborne fungal pathogens affecting curubit crop species growing in the desert areas. This is a unique and novel "systems" approach that has the potential to utilize natural plant adaptation for agricultural development. We envisage that endophyte-colonized melons will eventually be used to overcome damages caused by soilborne diseases and also for cultivation of this crop, under stress conditions, utilizing treated waste water, thus dealing with the limited resource of fresh water.

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Hasan, Jafrul A., Anwarul Huq et Rita R. Colwell. Evidence for Environmental Factors, Including Presence of Heavy Metals, Involved in Converting Potential Pathogens to a Viable But Nonculturable State in River and Estuarine Water. Fort Belvoir, VA : Defense Technical Information Center, mai 1991. http://dx.doi.org/10.21236/ada237512.

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Shpigel, Nahum Y., Ynte Schukken et Ilan Rosenshine. Identification of genes involved in virulence of Escherichia coli mastitis by signature tagged mutagenesis. United States Department of Agriculture, janvier 2014. http://dx.doi.org/10.32747/2014.7699853.bard.

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Mastitis, an inflammatory response of the mammary tissue to invading pathogenic bacteria, is the largest health problem in the dairy industry and is responsible for multibillion dollar economic losses. E. coli are a leading cause of acute mastitis in dairy animals worldwide and certainly in Israel and North America. The species E. coli comprises a highly heterogeneous group of pathogens, some of which are commensal residents of the gut, infecting the mammary gland after contamination of the teat skin from the environment. As compared to other gut microflora, mammary pathogenic E. coli (MPEC) may have undergone evolutionary adaptations that improve their fitness for colonization of the unique and varied environmental niches found within the mammary gland. These niches include competing microbes already present or accompanying the new colonizer, soluble and cellular antimicrobials in milk, and the innate immune response elicited by mammary cells and recruited immune cells. However, to date, no specific virulence factors have been identified in E. coli isolates associated with mastitis. The original overall research objective of this application was to develop a genome-wide, transposon-tagged mutant collection of MPEC strain P4 and to use this technology to identify E. coli genes that are specifically involved in mammary virulence and pathogenicity. In the course of the project we decided to take an alternative genome-wide approach and to use whole genomes bioinformatics analysis. Using genome sequencing and analysis of six MPEC strains, our studies have shown that type VI secretion system (T6SS) gene clusters were present in all these strains. Furthermore, using unbiased screening of MPEC strains for reduced colonization, fitness and virulence in the murine mastitis model, we have identified in MPEC P4-NR a new pathogenicity island (PAI-1) encoding the core components of T6SS and its hallmark effectors Hcp, VgrG and Rhs. Next, we have shown that specific deletions of T6SS genes reduced colonization, fitness and virulence in lactating mouse mammary glands. Our long-term goal is to understand the molecular mechanisms of host-pathogen interactions in the mammary gland and to relate these mechanisms to disease processes and pathogenesis. We have been able to achieve our research objectives to identify E. coli genes that are specifically involved in mammary virulence and pathogenicity. The project elucidated a new basic concept in host pathogen interaction of MPEC, which for the best of our knowledge was never described or investigated before. This research will help us to shed new light on principles behind the infection strategy of MPEC. The new targets now enable prevalence and epidemiology studies of T6SS in field strains of MPEC which might unveil new geographic, management and ecological risk factors. These will contribute to development of new approaches to treat and prevent mastitis by MPEC and perhaps other mammary pathogens. The use of antibiotics in farm animals and specifically to treat mastitis is gradually precluded and thus new treatment and prevention strategies are needed. Effective mastitis vaccines are currently not available, structural components and effectors of T6SS might be new targets for the development of novel vaccines and therapeutics.

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Rahimipour, Shai, et David Donovan. Renewable, long-term, antimicrobial surface treatments through dopamine-mediated binding of peptidoglycan hydrolases. United States Department of Agriculture, janvier 2012. http://dx.doi.org/10.32747/2012.7597930.bard.

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There is a need for renewable antimicrobial surface treatments that are semi- permanent, can eradicate both biofilms and planktonic pathogens over long periods of time and that do not select for resistant strains. This proposal describes a dopamine binding technology that is inexpensive, bio-friendly, non-toxic, and uses straight-forward commercially available products. The antimicrobial agents are peptidoglycanhydrolase enzymes that are non-toxic and highly refractory to resistance development. The goal of this project is to create a treatment that will be applicable to a wide variety of surfaces and will convey long-lasting antimicrobial activity. Although the immediate goal is to create staphylolytic surfaces, the technology should be applicable to any pathogen and will thus contribute to no less than 3 BARD priorities: 1) increased animal production by protecting animals from invasive and emerging diseases, 2) Antimicrobial food packaging will improve food safety and security and 3) sustainable bio- energy systems will be supported by coating fermentation vats with antimicrobials that could protect ethanolic fermentations from Lactobacillus contamination that reduces ethanol yields. The dopamine-based modification of surfaces is inspired by the strong adhesion of mussel adhesion proteins to virtually all types of surfaces, including metals, polymers, and inorganic materials. Peptidoglycanhydrolases (PGHs) meet the criteria of a surface bound antimicrobial with their site of action being extracellular peptidoglycan (the structural basis of the bacterial cell wall) that when breached causes osmotic lysis. As a proof of principle, we will develop technology using peptidoglycanhydrolase enzymes that target Staphylococcus aureus, a notoriously contagious and antimicrobial-resistant pathogen. We will test for susceptibility of the coating to a variety of environmental stresses including UV light, abrasive cleaning and dessication. In order to avoid resistance development, we intend to use three unique, synergistic, simultaneous staphylococcal enzyme activities. The hydrolases are modular such that we have created fusion proteins with three lytic activities that are highly refractory to resistance development. It is essential to use multiple simultaneous activities to avoid selecting for antimicrobial resistant strains. This strategy is applicable to both Gram positive and negative pathogens. We anticipate that upon completion of this award the technology will be available for commercialization within the time required to achieve a suitable high volume production scheme for the required enzymes (~1-2 years). We expect the modified surface will remain antimicrobial for several days, and when necessary, the protocol for renewal of the surface will be easily applied in a diverse array of environments, from food processing plants to barnyards.

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Harms, Nathan, Judy Shearer, James Cronin et John Gaskin. Geographic and genetic variation in susceptibility of Butomus umbellatus to foliar fungal pathogens. Engineer Research and Development Center (U.S.), août 2021. http://dx.doi.org/10.21079/11681/41662.

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Large-scale patterns of plant invasions may reflect regional heterogeneity in biotic and abiotic factors and genetic variation within and between invading populations. Having information on how effects of biotic resistance vary spatially can be especially important when implementing biological control because introduced agents may have different Impacts through interactions with host-plant genotype, local environment, or other novel enemies. We conducted a series of field surveys and laboratory studies to determine whether there was evidence of biotic resistance, as foliar fungal pathogens, in two introduced genotypes (triploid G1, diploid G4) of the Eurasian wetland weed, Butomus umbellatus L. in the USA. We tested whether genotypes differed in disease attack and whether spatial patterns in disease incidence were related to geographic location or climate for either genotype. After accounting for location (latitude, climate), G1 plants had lower disease incidence than G4 plants in the field (38% vs. 70%) but similar pathogen richness. In contrast, bioassays revealed G1 plants consistently received a higher damage score and had larger leaf lesions regardless of pathogen. These results demonstrate that two widespread B. umbellatus genotypes exhibit different susceptibility to pathogens and effectiveness of pathogen biological controls may depend on local conditions.

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Dickman, Martin B., et Oded Yarden. Modulation of the Redox Climate and Phosphatase Signaling in a Necrotroph : an Axis for Inter- and Intra-cellular Communication that Regulates Development and Pathogenicity. United States Department of Agriculture, août 2011. http://dx.doi.org/10.32747/2011.7697112.bard.

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The long-term goals of our research are to understand the regulation of sclerotial development and pathogenicity in S. sclerotiorum. The focus in this project is on the elucidation of the signaling events and environmental cues that contribute to broad pathogenic success of S. sclerotiorum. In this proposal, we have taken advantage of the recent conceptual (ROS/PPs signaling) and technical (genome sequence availability and gene inactivation possibilities) developments to address the following questions, as appear in our research goals stated below, specifically concerning the involvement of REDOX signaling and protein dephosphorylation in the regulation of hyphal/sclerotial development and pathogenicity of S. sclerotiorum. Our stated specific objectives were to progress our understanding of the following questions: (i) Which ROS species affect S. sclerotiorum development and pathogenicity? (ii) In what manner do PPs affect S. sclerotiorum development and pathogenicity? (iii) Are PPs affected by ROS production and does PP activity affect ROS production and SMK1? (iv) How does Sclerotinia modulate the redox environment in both host and pathogen? While addressing these questions, our main findings include the identification and characterization the NADPH oxidase (NOX) family in S. sclerotiorum. Silencing of Ssnox1 indicated a central role for this enzyme in both virulence and pathogenic (sclerotial) development, while inactivation of Ssnox2 resulted in limited sclerotial development but remained fully pathogenic. Interestingly, we found a consistent correlation with Ssnox1(involved with pathogenicity) and oxalate levels. This same observation was also noted with Sssod1. Thus, fungal enzymes involved in oxidative stress tolerance,when inactivated, also exhibit reduced OA levels. We have also shown that protein phosphatases (specifically PP2A and PTP1) are involved in morphogenesis and pathogenesis of S. sclerotiorum, demonstrating the regulatory role of these key proteins in the mentioned processes. While probing the redox environment and host-pathogen interactions we determined that oxalic acid is an elicitor of plant programmed cell death during S. sclerotiorum disease development and that oxalic acid suppresses host defense via manipulation of the host redox environment. During the course of this project we also contributed to the progress of understanding S. sclerotiorum function and the manipulation of this fungus by establishing an efficient gene replacement and direct hyphal transformation protocols in S. sclerotiorum. Lastly, both PIs were involved in thegenomic analysis of this necrotrophic fungal pathogen (along with Botrytis cinerea). Our results have been published in 11 papers (including joint papers and refereed reviews) and have set the basis for a continuum towards a better understanding and eventual control of this important pathogen (with implications to other fungal-host systems as well).

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Splitter, Gary A., Menachem Banai et Jerome S. Harms. Brucella second messenger coordinates stages of infection. United States Department of Agriculture, janvier 2011. http://dx.doi.org/10.32747/2011.7699864.bard.

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Aim 1: To determine levels of this second messenger in: a) B. melitensiscyclic-dimericguanosinemonophosphate-regulating mutants (BMEI1448, BMEI1453, and BMEI1520), and b) B. melitensis16M (wild type) and mutant infections of macrophages and immune competent mice. (US lab primary) Aim 2: To determine proteomic differences between Brucelladeletion mutants BMEI1453 (high cyclic-dimericguanosinemonophosphate, chronic persistent state) and BMEI1520 (low cyclicdimericguanosinemonophosphate, acute virulent state) compared to wild type B. melitensisto identify the role of this second messenger in establishing the two polar states of brucellosis. (US lab primary with synergistic assistance from the Israel lab Aim 3: Determine the level of Brucellacyclic-dimericguanosinemonophosphate and transcriptional expression from naturally infected placenta. (Israel lab primary with synergistic assistance from the US lab). B. Background Brucellaspecies are Gram-negative, facultative intracellular bacterial pathogens that cause brucellosis, the most prevalent zoonosis worldwide. Brucellosis is characterized by increased abortion, weak offspring, and decreased milk production in animals. Humans are infected with Brucellaby consuming contaminated milk products or via inhalation of aerosolized bacteria from occupational hazards. Chronic human infections can result in complications such as liver damage, orchitis, endocarditis, and arthritis. Brucellaspp. have the ability to infect both professional and non-professional phagocytes. Because of this, Brucellaencounter varied environments both throughout the body and within a cell and must adapt accordingly. To date, few virulence factors have been identified in B. melitensisand even less is known about how these virulence factors are regulated. Subsequently, little is known about how Brucellaadapt to its rapidly changing environments, and how it alternates between acute and chronic virulence. Our studies suggest that decreased concentrations of cyclic dimericguanosinemonophosphate (c-di-GMP) lead to an acute virulent state and increased concentrations of c-di-GMP lead to persistent, chronic state of B. melitensisin a mouse model of infection. We hypothesize that B. melitensisuses c-di-GMP to transition from the chronic state of an infected host to the acute, virulent stage of infection in the placenta where the bacteria prepare to infect a new host. Studies on environmental pathogens such as Vibrio choleraeand Pseudomonas aeruginosasupport a mechanism where changes in c-di-GMP levels cause the bacterium to alternate between virulent and chronic states. Little work exists on understanding the role of c-di-GMP in dangerous intracellular pathogens, like Brucellathat is a frequent pathogen in Israeli domestic animals and U.S. elk and bison. Brucellamust carefully regulate virulence factors during infection of a host to ensure proper expression at appropriate times in response to host cues. Recently, the novel secondary signaling molecule c-di-GMP has been identified as a major component of bacterial regulation and we have identified c-di-GMP as an important signaling factor in B. melitensishost adaptation. C. Major conclusions, solutions, achievements 1. The B. melitensis1453 deletion mutant has increased c-di-GMP, while the 1520 deletion mutant has decreased c-di-GMP. 2. Both mutants grow similarly in in vitro cultures; however, the 1453 mutant has a microcolony phenotype both in vitro and in vivo 3. The 1453 mutant has increased crystal violet staining suggesting biofilm formation. 4. Scanning electron microscopy revealed an abnormal coccus appearance with in increased cell area. 5. Proteomic analysis revealed the 1453 mutant possessed increased production of proteins involved in cell wall processes, cell division, and the Type IV secretion system, and a decrease in proteins involved in amino acid transport/metabolism, carbohydrate metabolism, fatty acid production, and iron acquisition suggesting less preparedness for intracellular survival. 6. RNAseq analysis of bone marrow derived macrophages infected with the mutants revealed the host immune response is greatly reduced with the 1453 mutant infection. These findings support that microlocalization of proteins involved in c-di-GMP homeostasis serve a second messenger to B. melitensisregulating functions of the bacteria during infection of the host.

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