Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item Development of a Multilocus Sequence Typing Scheme for Avibacterium paragallinarum(2023) Harris, Alyssa Meihua; Ghanem, Mostafa; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Avibacterium paragallinarum (A. paragallinarum), the causative agent of the respiratory disease Infectious Coryza (IC) in chickens, has seen a rising incidence in the United States. Current strain differentiation is inadequate for detailed epidemiological analysis. The objective of this study was to develop a Multilocus sequence typing (MLST) scheme for A. paragallinarum for outbreak investigations and to offer a better tool for strain differentiation. By evaluating whole genome sequences and clinical samples, we designed PCR amplicons for eighteen gene segments, selected six genes for their nucleotide diversity and discrimination potential. The MLST was used to differentiate seventy-five samples. Our MLST showed greater discriminatory power than existing HPG2-based methods, aligning closely with adhoc core genome MLST in 75 tested sample. Our newly developed MLST scheme enables more accurate strain differentiation, allowing for better understanding of A. paragallinarum epidemiology and population structure to help prevention and control efforts worldwide.Item CAUSATIVE AGENTS FOR FOWL TYPHOID AND PULLORUM DISEASE IN POULTRY AND APPROACH TO CONTROL(2023) Julianingsih, Dita; Biswas, Debabrata; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In response to escalating consumer demand, a significant number of conventional US poultry farms have transitioned to antibiotic-free and chemical-free practices, particularly those adopting pasture/organic methods. However, recent reports highlight a resurgence of bacterial diseases in both conventional and pasture poultry farms, resulting in elevated bird mortality rates and reduced profitability. This comprehensive study investigates the prevalence of S. Gallinarum and S. Pullorum, causative agents of fowl typhoid and pullorum disease, in integrated crop-livestock/pasture farm environments and meat products. A total of 1,286 samples from 7 farms and 13 retail markets were examined, revealing that S. Pullorum and S. Gallinarum are common in both farm poultry environments and market products. Antibiotic resistance patterns, determined through an antibiogram assay, indicated high resistance to multiple antibiotics. S. Pullorum and S. Gallinarum were discovered in 2.7% and 1.5% of samples, respectively, at the pre-harvest stage. Only 1.6% of the meat samples recovered from retail markets had S. Gallinarum detected in them at the post-harvest level. Concurrently, a different study investigates the possibility of Orange Cold-press Valencia Terpeneless, a citrus oil variety, acting as a natural antimicrobial in poultry farming. This study tackles the problems caused by a decline in the usage of antibiotics, which has resulted in an increase in bacterial infections. Citrus oil exhibits potential as an antimicrobial agent, inhibiting the growth of S. Pullorum and S. Gallinarum, with consistent MIC and MBC values. Time-dependent experiments with 0.4% citrus oil show total suppression of bacterial growth, which is confirmed by environmental simulations. Furthermore, the study reveals that both Salmonella strains have downregulated their virulence genes, which may indicate a change in the pathogenicity of the bacteria. Overall, the findings highlight the crucial importance of surveillance programs and preventive measures. Citrus oil is presented as a promising natural alternative for antibiotics in the treatment of Salmonella-related infections in the poultry farming industry.Item The study of hyperketonemia in the dairy cow.(2023) Barrientos-Blanco, Mario Alberto; Rico, Eduardo; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The metabolic phenomenon of ketosis in dairy cows has remained ambiguous, casting uncertainty over our understanding and its real implications. Ketosis, commonly defined as blood β-hydroxy-butyrate (BHB) ≥ 1.2 mM (i.e., hyperketonemia), has been observationally connected to the onset of peripartal metabolic disorders (e.g., infectious diseases, fatty liver), and reduced milk yield in dairy cows. Although BHB is currently used as standard biomarker for the prediction of negative health and performance outcomes during the peripartum, the nature of this relationship is ambiguous. In contraposition, recent discoveries in mammalian biology indicate BHB as therapeutic metabolite (e.g., alleviation of inflammation and oxidative stress). Our overreaching goal was to study the effects of BHB on dairy cow metabolism and health. In our first study, 6 multiparous (parity = 2.8 ± 0.9) Holstein mid-lactation dairy cows (128 ± 52 days in milk; DIM), were enrolled in a study to evaluate a ketogenic diet using calcium butyrate (—CaBu—; a ruminal ketone precursor) against an un-supplemented control (Control) in a crossover arrangement of treatments. The CaBu resulted in nutritional ketosis (P < 0.05) with blood BHB levels of 0.2 mM higher relative to Control. Although CaBu resulted in reduced dry matter intake (DMI; P < 0.05), milk production was not affected (P > 0.40), and feed efficiencies were improved (P < 0.05) relative to Control. No differences in glucose, NEFA, respiration rates, pain scores, or rectal temperatures were observed between treatments. In the second experiment, 8 multiparous Holstein (2.75 ± 0.89) mid-lactation dairy cows (140 ± 48 DIM), feed ad libitum, were enrolled in a in a crossover arrangement of treatments. The aim of the study was to evaluate the effect of ketones by intravenous infusion of either Na-BHB solution (2.5mM; EK) to sustain hyperketonemia —BHB > 1.2 mM and < 3.0 mM—, or NaCl as a control (2.5mM; Control) over a 72h period. A systemic lipopolysaccharide (LPS) challenge (E. coli 055:B5; 0,085 g/kg BW,) was intravenously administered at h 60 from infusion start. Cows sustained hyperketonemia throughout the 72h experimental period (1.4 BHB mM vs. 0.7 BHB mM in EK vs. Control, respectively). While DMI and milk production were not affected by the BHB infusion, the combination with the LPS challenge resulted in reductions of 20.8% (P < 0.05) and 40.1%, (P = 0.14) for both measurements in EK vs. Control, respectively. No differences were detected in the glucose and NEFA concentrations, but insulin was higher 46.6% (P < 0.05) in EK group. Among the immune markers, IL-1 was 30.8% higher (P < 0.05) in the EK group, and not differences were detected in TNF, IL-10, CRP, and caspase-1. As expected, the LPS challenge induced increased respiration rates, temperature, and pain scores over the time course of the evaluation (P < 0.001); however, respiration rates tended to be reduced in 8.4% (P < 0.1) and rectal temperature increased in 0.3% (P < 0.05) by the BHB treatment (P < 0.05). Our results are indicative that, in the absence of an immune challenge, hyperketonemia results in no negative impact on cow productivity and health. These data add support to our hypothesis that cofactors other than ketones may be necessary for the development of negative trajectories of health and performance of lactating dairy cows. Future studies will be required to confirm that BHB hyperketonemia metabolic effects could differ from ketosis disorder in dairy cows.Item HEPATITIS E VIRUS MODULATES HOST FACTORS TO GENERATE A CONDUCIVE ENVIRONMENT FOR REPLICATION(2020) lin, shaoli; Zhang, Yanjin; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hepatitis E virus (HEV) is one of the causative agents for liver inflammation across the world. HEV infection mainly presents as acute and self-limiting hepatitis in young adults. However, it can be exacerbated to fulminant hepatitis in HEV-infected pregnant women, resulting in up to 30% case fatality. Besides, chronic HEV infection with rapid progression in immunocompromised patients has been a challenge in many countries since it was reported years ago. HEV infection is zoonotic, and human HEV strains are grouped into four major genotypes in the genus Orthohepevirus A, the family Hepeviridae. Among the four genotypes, genotype 1 and 2 are obligate human pathogens, and genotype 3 and 4 cause zoonotic infections. Due to the lack of an effective cell culture system and a proper animal model, HEV biology, virus-cell interactions, and pathogenesis are understudied. HEV is known to inhibit the innate immune response by targeting type I interferon (IFN) signaling pathway via its ORF1 products. Nevertheless, it remains largely unknown how the virus manipulates host factors to facilitate its replication. The objective of these studies was to elucidate the mechanism of HEV manipulation of host factors to generate a conducive environment for replication. Our results show that the capsid protein of HEV inhibits the IFN production to dampen the antiviral response through its N-terminal arginine-rich motif. In addition to the impairment of innate immunity, HEV proliferation requires the presence of other host factors: DDX3, an RNA helicase, and oxysterol-binding protein (OSBP), a lipid transporter. The knockdown of these two factors led to a significant reduction of HEV replication, whereas the reconstitution of these two genes restores the HEV proliferation level. The capsid protein was found to interact with the C-terminal domain of DDX3. The HEV helicase was shown to interact with OSBP and block its translocation to the Golgi apparatus. These results indicate that HEV employs multiple strategies including blocking antiviral response and recruiting host factors for its invasion and proliferation. Our data provide insights into the HEV-cell interactions and may facilitate the development of novel antiviral strategies.Item Studies on gizzard ulceration in chickens(1941) Tepper, Albert Edward; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item Bacteria as secondary invaders in blackhead livers of turkeys(1952) Harrison, Arthur Pennoyer; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item Diagnostic tests including hemotology in swine brucellosis and capsule formation in Brucella(1943) Cotton, Cornelia Marie; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item In Vitro Study of an Orange Oil Derived Alternative to Antibiotics in the Treatment of Bovine Mastitis(2015) Federman, Cassandra Skye; Biswas, Debabrata; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bovine mastitis is a costly disease in the U.S. dairy industry. Its major causative agent Staphylococcus aureus is often unresponsive to antibiotic therapy. Our first study examined terpeneless, cold-pressed Valencia (CPV) orange oil as a possible alternative to antibiotic therapy in the treatment of S. aureus associated bovine mastitis. Orange oil showed significant inhibition of S. aureus growth and invasion of bovine epithelial mammary cells, but only modest reductions in pre-formed biofilms, which contribute to persistence of S. aureus infections. Our second study examined major components of terpeneless, CPV orange oil. Of four major compounds tested, only citral and linalool had significant inhibitory effects on S. aureus growth. In addition, they were capable of reducing pre-formed biofilms as well as association and invasion to bovine epithelial mammary cells. Part of this inhibition was due to downregulation of virulence and biofilm genes.Item Lineage reprogramming of tumor-infiltrating cytotoxic T lymphocytes using protein stem cell transcription factors(2015) BhaduriHauck, Anjuli Lucija; Xiao, Zhengguo; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Adoptive cell transfer therapy (ACT) is one of the most promising immunotherapies against cancer. However, this treatment regimen requires the expansion of a small population of effector cells, known as tumor infiltrating lymphocytes, into the billions in order to overcome the immunosuppressive tumor microenvironment. The cytotoxic T lymphocytes (CTLs) within this invading immune cell population are the most critical components to kill the growing cancer cells. Nonetheless, the rapid expansion of already exhausted tumor-infiltrating cytotoxic T lymphocytes (TICTLs) may further push them to a terminally differentiated state that reduces their proliferative response upon antigen stimulation. Recently, induced pluripotent stem cells (iPSCs) generated from TICTLs have been suggested as a way to create a renewable source of rejuvenated tumor-specific CTLs, but retroviral reprogramming is inefficient, and can lead to an increased chance of tumorigenesis. To improve the expansion of TICTLs, we used transient protein exposure to SOX2, OCT4, and NANOG (SON) in order to push these exhausted TICTLs to a less differentiated stage, preferably stem cell-like memory CTLs (Tscm). These three transcription factors were transiently delivered using a nuclear protein delivery system. We found only the TICTLs treated with SON (STICTLs) exhibited an increased proliferation rate and extended survivability, independent of additional cytokines and antigen stimulation both in vitro and in vivo; effector CTLs did not respond to the SON regimen. These highly proliferative STICTLs could be associated with up regulation of certain genes related in cell cycle control, such as cyclin D1. Though these STICTLs still express a T cell receptor (TCR), as well as many critical downstream components, they were unable to elicit a reaction against antigen exposure. Though clearly not iPSCs, it is possible that the SON treatment had pushed the TICTLs into a state similar to an early double negative thymocyte. Our findings indicate that TICTLs are uniquely responsive to protein SON compared to naïve and effector CTLs; suggesting TICTLs may also be sensitive to regulation by other more lineage specific transcription factors, thus present new avenue for cancer immune therapy.Item Development of methods to test drug sensitivity of fish pathogenic Flavobacterium columnare and drug sensitivity thresholds for F. columnare to the antimicrobial florfenicol.(2015) Gieseker, Charles Michael; Woods III, Lewis C.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Antimicrobial drugs play a key role in managing the health of fish in aquaculture. However, public health concerns about antimicrobial resistance--the ability of microorganisms to resist standard antimicrobial treatments--include the potential for antimicrobial use in aquaculture to select for resistant bacteria in and around fish farms. Recent approval of two antimicrobial drugs to treat farmed freshwater fish with infections caused by the aquatic bacteria Flavobacterium columnare and F. psychrophilum created an important need for research to monitor these bacteria for changes in antimicrobial susceptibility and to decide when the antimicrobials should be used. Therefore three studies were conducted. The initial study optimized methods for broth microdilution testing F. columnare and F. psychrophilum and conducted a multi-laboratory standardization trial that set quality control parameters for nine antimicrobials commonly used in aquaculture, thus creating the first standardized testing method. In the second study, we constructed frequency distributions using minimal inhibitory concentrations determined from testing 134 F. columnare with the standardized method. Analysis of the distributions determined the drug concentration--called an epidemiological cutoff value (ECV)--which separated the wild type isolates with no acquired or selected resistance from the non-wild type isolates. The ECV indicated 22 of 134 isolates had decreased their susceptibility to at least 1 antimicrobial. In addition, we developed a laboratory disease model with juvenile channel catfish, Ictalurus punctatus. We compared the virulence of three F. columnare isolates with wild type or three isolates with non-wild type florfenicol susceptibility using the model. We found that five isolates had similar high level virulence and were not affected by differences in florfenicol susceptibility. Finally, we studied if decreased non-wild type florfenicol susceptibility affected the ability of the approved florfenicol treatment to control F. columnare infections. The approved treatment significantly reduced catfish mortality following exposure to an isolate with typical wild type florfenicol susceptibility but mortality was not reduced following exposure to an isolate with non-wild type susceptibility. Taken together, these studies provide methods and research needed to monitor F. columnare for changes in antimicrobial susceptibility and to rationally use florfenicol to control F. columnare infections.