Browsing by Subject "Pathogen"

Now showing 1 - 7 of 7
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    Atmospheric Pressure Non-Thermal Plasma: A Tool for Inactivating Airborne Pathogens
    (2019-12) Schiappacasse, Charles
    Pathogens spread by airborne transmission represent a persistent threat to economic stability and human/animal health. These pathogens are particularly prevalent in the agricultural sector, especially in animal rearing facilities. However, the agricultural industry currently lacks an efficient and cost effective means of controlling airborne pathogens. The present study explored the possibility of developing a new type of antimicrobial air treatment system based on non-thermal plasma technology. The study consisted of an initial laboratory testing stage followed by a pilot scale study performed in a local poultry rearing facility. During the laboratory testing stage two prototype non-thermal plasma reactors were developed and challenged in a closed air circulation system with artificially aerosolized Newcastle Disease Virus and avian influenza virus. The results indicated that both viruses could be rapidly inactivated below the limit of detection after sub second exposure to non-thermal plasma. Specifically, Newcastle Disease Virus was completely inactivated after 7.7x10-3 seconds of direct plasma treatment with a specific energy input of 171 J/L of air. Although the high virus inactivation effects are believed to predominately be attributable to direct non-thermal plasma exposure, preliminary experiments revealed that liquid-based virus collection strategies (e.g. use of an SKC BioSampler) were susceptible to liquid-based inactivation of collected viruses via indirect non-thermal plasma exposure. Attempts were made to circumvent the issue of liquid-based inactivation by employing a gelatin-filter based virus collection strategy. However, due to the high ozone emissions (80ppm) of the non-thermal plasma reactors, surface-based inactivation effects of viruses collected on the filters could not be ruled out as a contributing mechanism to the high virus inactivation rates. Due to biosafety concerns, flow rates >28LPM were not tested and the upper limit of non-thermal plasma’s virus inactivation efficiency was not determined. Additionally, virus samples taken from the 6-jet collision nebulizer, used to aerosolize viruses in this study, revealed that nebulization stress did not contribute to virus inactivation. Finally, the effects of relative humidity on virus losses within the closed air circulation system were explored. Findings showed a strong correlation (R2>0.99) between increasing relative humidity and decreasing airborne virus concentrations. This relationship is thought to predominately be due to humid aerosols experiencing greater condensation losses within the closed air circulation system when compared with less humid aerosols. However, the small volume of condensed solution visualized within the system was not sufficient to account for all of the viruses lost between the nebulizer and sampling port (gelatin filters). Correcting for adhesion losses and possible low gelatin filter sampling efficiencies did not completely account for non-plasma treated viral losses. Therefore, it is possible that the viruses used in the present study experience a decrease in infectivity with increasing humidity levels. The second stage of this study involved the design and fabrication of a pilot scale non-thermal plasma air treatment system and challenging it with ambient aerobic bacteria at a local turkey barn. Technical complications with a commercial high voltage power supply resulted in the pilot scale system operating at approximately 10% of its specified input power resulting in a specific energy input of only ~19.4 J/L. As a result, the pilot system was not able to reduce airborne bacteria concentrations relative to air samples that did not receive plasma treatment. Overall, the findings from the present study indicate that non-thermal plasma based air treatment technologies can be an effective tool for controlling airborne pathogens. However, the successful industrial implementation of this technology will require appropriate power supplies and methods to mitigate ozone emissions.
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    Database of publications on swine diseases, 1966-2016
    (2018-01-04) VanderWaal, Kimberly; kvw@umn.edu; VanderWaal, Kimberly
    A database of publications generated from literature searches for 40 priority swine pathogens using ISI's Web of Science, Scopus, and PubMed.
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    Evaluating the antimicrobial mechanism of neutral electrochemically activated water on foodborne pathogens and their biofilms
    (2012-12) Yang, Hongshun
    Sanitizing is a key step in ensuring food safety. Neutral electrochemically activated water (NECAW) not only has antimicrobial effects but also is relatively friendly to handlers and foods, and it complies with organic food practices. However, its antimicrobial effects on different pathogens and strains have not been examined and its antimicrobial mechanisms are not fully understood. The goal of this project was to investigate the use of NECAW as a sanitizer in inactivating foodborne pathogens. The first objective of this study was to determine the effectiveness and broadspectrum activity of NECAW against foodborne pathogens. The sanitizing efficacy of NECAW against 40 different strains of E. coli O157:H7, L. monocytogenes, and Salmonella as liquid cultures, dried cells on stainless steel (SS) surfaces, and biofilms on SS was examined. It was found that NECAW with 100 mg/l free available chlorine (FAC) caused more than 5 log CFU/ml reductions for all strains in liquid culture, more than 3 log CFU/coupon reductions for 92.5% of the strains dried on stainless steel (SS) surfaces and for 27.5% of biofilms. Among all the strains, S. Newport B4442CDC was the most resistant strain to NECAW on surfaces while E. coli O157:H7 ATCC 43895 was the most resistant strain in biofilms and liquid pure cultures. Overall, NECAW was effective and had a broad-spectrum activity against foodborne pathogens. The second objective was to evaluate the sanitizing effect of NECAW and other commercial ‘active water’ technologies on foodborne pathogens. Five individual strains of each foodborne pathogen including E. coli O157:H7, L. monocytogenes, and Salmonella as liquid cultures and dried cells on stainless steel surfaces were studied by iv comparing the sanitizing effect of NECAW and available commercial technologies on these pathogens. The results showed that 100 mg/l ECAW had sanitizing effects of at least 5 log CFU/ml reductions on liquid culture and more than 4 log CFU/coupon reductions for pathogens dried on SS surfaces. In contrast, the other commercial technologies tested were not effective in sanitizing. They, however, washed the bacteria off the surface into rinse water, which would lead to a significant safety concern of cross contamination. The third objective of this study was to examine the three dimensional morphology of foodborne pathogen biofilms using atomic force microscopy (AFM). AFM experiments were conducted by directly imaging the three-dimensional morphology of the foodborne pathogens biofilms (five strains for each pathogen), and imaging the biofilms pre- and post-NECAW treatment. Images of AFM showed tree-like structures as well as individual cells. L. monocytogenes biofilms had a higher percentage of tree-like structures than E. coli O157:H7 and Salmonella. The biofilm structures and microbial cells on SS were destroyed by the treatment with NECAW according to the AFM study, providing morphological evidence that NECAW was effective in controlling surface contamination of pathogenic bacteria and biofilm growth. The fourth objective of this study was to assess the role of sigB and inlA genes in L. monocytogenes biofilm formation and the antimicrobial efficacy of NECAW treatment on L. monocytogenes. The expression levels of sigB and inlA genes were investigated by using qPCR, and sanitizing effects of NECAW on wild-type (WT) and sigB/inlA mutant L. monocytogenes strains were determined by the direct plating method. After NECAW v treatment, expression of both genes increased for the WT. While sigB gene expression of the ΔinlA strain increased to a level comparable to that of the WT, inlA gene expression of the ΔsigB strain did not significantly increase. Both genes were expressed more in biofilms than in liquid cultures. The level of inlA gene expression in WT increased by 4.28 and 5.51-fold by treatment with 4 mg/l NECAW for 10 min in liquid cultures and biofilms, respectively, while the corresponding values were 5.91 and 10.05-fold for the sigB gene. Mutant strains were more sensitive to NECAW treatment than the WT strain. The sigB gene was more important than inlA for the pathogen’s survival under NECAW treatment. Surviving L. monocytogenes cells post-sublethal NECAW treatment might become resistant to further sanitizer treatment.
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    Pathogen Quantification and Risk Assessment of Water Reuse Systems in the State of Minnesota
    (2019-12) Dooling, Valerie
    There is a growing interest in reusing or reclaiming water for non-potable use; however, one of the largest barriers to implementation is unknown source water quality and what risks are present. This work was conducted to determine the number of pathogens and their concentration present in currently operational water reuse systems in Minnesota, and to collect design treatment information from each reuse site and compare to pathogen and indicator quantity. Eighty-three samples were collected from 25 sites and were simultaneously analyzed for 27 bacterial and viral genes through microfluidic qPCR. Findings are that indicators and chemical tests did not correlate with type of source water. Type of treatment does not consistently correlate to log10 reduction, and only wastewater disinfection consistently removed all pathogens from treatment. Ten different pathogens were detected in water reuse systems. Quantitative Microbial Risk Assessment was performed on six pathogens in four exposure scenarios. Findings are that annual risk of infection of non-treated water is greater than recreational water benchmarks, however, the extent of risks depend on the exposure. When only considering samples from distribution or post-treatment sites, the risks are considerably lower, and often within guidelines.
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    A Source to Tap Investigation of Minnesota's Groundwater Supplies Used for Drinking Water
    (2018-11) Galt, John
    Groundwater is often a desirable drinking water source because it is generally free of suspended solids and microbial pathogens and thus requires minimal, if any, treatment prior to distribution. Epidemiological studies have shown, however, that consumption of untreated groundwater increases risk of gastrointestinal illness. Previous work in Wisconsin, USA reported the occurrence of pathogenic viruses in groundwater supplies and resulting health impacts but bacterial pathogens were not investigated. In this study, a high-volume (300 – 1500 L) dead-end ultrafiltration sampling method was used to capture and recover microbes from 16 public groundwater systems throughout the State of Minnesota. The systems were sampled at the wellhead or source, after treatment if any (i.e., two systems did not treat or disinfect before distribution), and from one location in the distribution system. DNA was extracted from the microbes recovered in these samples and used as template for quantitative PCR analyses targeting 14 genes corresponding to pathogenic bacteria, one gene for a DNA virus, and the 16S rRNA gene as a marker for total bacteria. All samples were negative for the targeted genes from Campylobacter jejuni, Shigella spp., and Adenovirus; Escherichia coli-specific genes were only detected in water from a non-potable well with a documented history of contamination. Genes markers for two genera, Legionella and Mycobacteria, that include species that are opportunistic pathogens, were detected in four of the 16 public groundwater supplies, with Legionella levels decreasing in disinfected systems while Mycobacteria levels tended to increase. Raw water 16S rRNA gene concentrations ranged from 10^5 – 10^8 gene copies/L, decreased to background levels after disinfection, then rebounded at the tap in the majority of cities. There was no significant difference in 16S rRNA gene concentrations from source-to-tap in the two non-disinfecting cities. Raw water samples contained diverse and previously uncharacterized organisms as revealed by DNA sequencing analyses, and beta diversity analyses suggest that community composition is driven by source water and/or disinfection. The results from this study suggest that groundwaters supplying public water systems in Minnesota are largely free of enteric pathogens but may contain opportunistic pathogens.
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    Streptococcus cristatus modulates epithelial innate immune response through regulating nuclear factor-kappa B pathway.
    (2009-12) Zhang, Guizhen
    Streptococci are the dominant oral commensal organisms. They, along with putative periodontal pathogens, normally colonize multiple oral tissue sites. An emerging paradigm indicates that the host can distinguish between pathogenic and nonpathogenic stimuli, and commensal bacteria could modulate expression of host genes to contribute to mucosal tolerance. Here, I hypothesized that an oral commensal Streptococcus cristatus can attenuate epithelial proinflammatory response to Fusobacterium nucleatum via regulation of Toll-Like Receptor (TLR) signaling, as a mechanism for oral mucosal tolerance to polymicrobial infection. I first demonstrated that S. cristatus itself did not provoke IL-8 production in epithelial cells, and it was able to inhibit IL-8 responses to several putative oral pathogens including F. nucleatum. The inhibitory effect of S. cristatus on IL-8 was independent of its viability and its coaggregation with F. nucleatum, was not related to soluble bacterial products, and appeared to require bacterial contact with epithelial cells. Similar effects were seen with several other species of oral streptococci. Next, I performed pathway-specific microarray analysis to specifically monitor host gene modulation by S. cristatus on a broad scale. I found that S. cristatus altered the F. nucleatum–induced expression of a number of proinflammatory cytokine genes. Profiling of TLR signaling related genes revealed that S. cristatus most significantly impacted the downstream pathways, especially NF-κB, rather than altering TLRs and their adaptors and interacting proteins. Lastly, I examined the underlying mechanism(s) involved in the modulating effect of S. cristatus by looking specifically at its impact on the nuclear factor kappaB (NF-κB) pathway under the Toll-like receptor signaling background. I found that the IL-8 suppression by S. cristatus was coincident with the inhibition of NF-κB activation and IκB-α degradation. Pre-incubation with TLR2 and TLR4 antibodies, however, did not affect the epithelial response to either species alone or in combination. I thus conclude that the oral commensal S. cristatus is not only tolerated by the host, but also able to modulate host inflammatory response to pathogenic species through inhibiting IκB-NF-κB signaling module. The anti-inflammatory effect of S. cristatus might represent a regulatory mechanism present at the epithelial surface to tolerate polymicrobial colonization.
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    Will climate change influence disease susceptibility? a study of natural polyploids with manipulated flowering time exposed to contrasting water-availability conditions
    (2013-05) Toldo, Jessalyn R.
    Climate change is already influencing the prevalence and distribution of plant disease, posing a potential threat to native species. For plant populations that include mixed ploidy levels, diploids and polyploids may differ in their response to changing abiotic and biotic factors because of divergence in morphology, phenology, or plasticity in these traits. To examine how these factors influence the incidence of powdery mildew, I used diploid and tetraploid Solidago altissima lineages that had been artificially selected to expand the breadth of flowering time and subjected them to contrasting water availability treatments. I also tracked the maternal effects of both water availability and mildew infection on offspring. In general, powdery mildew infection was more widespread in wetter sites and treatments. I also found that ploidy level influenced the amount of powdery mildew cover on the plants, and this may be caused by innate differences in morphology and phenology between diploid and tetraploid cytotypes. Within each ploidy level, the extent of disease damage was higher among earlier flowering genotypes suggesting that advanced flowering phenology may result in increased duration of exposure to pathogens. Finally, maternal infection and water availability has consequences for offspring fitness and robustness. This work indicates that the genetic composition of plants may influence their disease susceptibility in a changing climate, and phenological changes influence plant fitness in response to disease.