Biology Commons^™

Characterization Of Staphylococcus Aureus Lipase, Vithooshan Vijayakumaran

Electronic Thesis and Dissertation Repository

USA300, a strain of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA), has become prevalent in the community. Colonization of human skin requires mechanisms that allow this bacterium to overcome the innate immune defenses on the skin, including secretion of antimicrobial lipids. Antimicrobial lipids inhibit S. aureus growth and induce the staphylococcal proteolytic cascade, producing aureolysin (Aur) which processes the lipase glycerol ester hydrolase (Geh). Nearly all S. aureus strains secrete Geh, yet little information exists concerning its function. Using purified Aur and Geh we confirm that aureolysin processes proGeh to Geh. We then confirmed that geh was required for lipase activity …

Role Of Branched-Chain Amino Acid Transporters In Staphylococcus Aureus Virulence, Sameha Omer

Electronic Thesis and Dissertation Repository

Branched-chain amino acids (BCAAs) act as effector molecules that signal a global transcriptional regulator, CodY, to regulate virulence factors in nutrient depleted environments. Staphylococcus aureus contains three putative BCAA transporters (BrnQ1, BrnQ2, BrnQ3) whose role in BCAA uptake is unknown. We hypothesize that BrnQ transporters are involved in BCAA uptake and contribute to virulence in S. aureus by modulating CodY activity. Results from radioactive uptake assays indicate that BrnQ1 is the predominant BrnQ transporter of isoleucine, valine and leucine. Meanwhile, BrnQ2 is more specific for isoleucine. Furthermore, only the lack of BrnQ1 hinders growth of S. aureus in chemically-defined media …

Modeling Leafhopper Populations And Their Role In Transmitting Plant Diseases., Ji Ruan

Electronic Thesis and Dissertation Repository

This M.Sc. thesis focuses on the interactions between crops and leafhoppers.

Firstly, a general delay differential equations system is proposed, based on the infection age structure, to investigate disease dynamics when disease latencies are considered. To further the understanding on the subject, a specific model is then introduced. The basic reproduction numbers $\cR_0$ and $\cR_1$ are identified and their threshold properties are discussed. When $\cR_0 < 1$, the insect-free equilibrium is globally asymptotically stable. When $\cR_0 > 1$ and $\cR_1 < 1$, the disease-free equilibrium exists and is locally asymptotically stable. When $\cR_1>1$, the disease will persist.

Secondly, we derive another general delay differential equations system to examine how different life stages of leafhoppers affect crops. The basic reproduction numbers $\cR_0$ is determined: when …

Mechanisms Contributing To The Emergence Of Ranavirus In Ectothermic Vertebrate Communities, Roberto M. Brenes

Doctoral Dissertations

Ranaviruses have been linked to amphibian die-off events in ectothermic vertebrates worldwide. Differences in susceptibility and capacity of transmission among and within classes are poorly understood. My goal was to determine possible mechanisms influencing susceptibility to ranavirus infection in amphibian species and other aquatic vertebrate taxa, as well as the capacity of transmission between classes and the effects of amphibian community composition on ranavirus transmission. I tested 16 amphibian species from USA, Europe, and the pet trade, expanding an existing database developed by the Center for Wildlife Health to 35 amphibian species from 9 families. I also tested the susceptibility …

Role Of Msa In Immune Evasion, Persistence, And Protease Regulation In The Human Pathogenic Strains Of Staphylococcus Aureus, Maria Deepa Basco

Dissertations

Opportunistic pathogens like Staphylococcus aureus on entering the host can stay colonized at the foci of infection or evade the immune system to disseminate to other sites. In this study we investigated the regulatory influence of the modulator of sarA (msa) on immune evasion and host persistence, employing the hospital-acquired strain S. aureus UAMS-1 and community-acquired strain S. aureus USA300 LAC. In the murine sepsis model, mutation of the msa gene in LAC showed no change in dissemination of infection; however, in UAMS-1 a decrease in microbial load was observed in the lungs. Differential regulation by the msa gene was …

Trends In Borrelia Spp. Prevalence In Ixodes Spp. Ticks From The Southeastern Coastal United States, Lauren Paul Maestas

Masters Theses

The Lyme borreliosis (LB) cycle, involving Ixodes scapularis and Borrelia burgdorferi sensu stricto (Bbss), is well documented in the northeastern US, where LB is becoming increasingly prevalent. In coastal North Carolina, I. affinis has been shown to have a higher incidence of Bbss than I. scapularis. My objectives were, to assess changes in prevalence of Bbss in Ixodes spp. along a transect from Virginia to Florida, and to assess the value of dogs and mesomammals as sentinels for spread of Borrelia burgdorferi sensu lato.

Ixodes spp. were collected at sites from 37.4^o N to 30.0^{o …}

Prevalence And Transmission Potential Of Borrelia Burgdorferi In Three Species Of Wildcaught Plestiodon Spp. Skinks Of The Southeastern United States, Teresa Dianne Moody

Masters Theses

In the southeastern United States, blue-tailed skinks (Plestiodon spp.) are important hosts for Ixodes scapularis ticks, the principal vector of Lyme disease (LD) in this region. Skinks and other southeastern lizards are not thought to be reservoir competent for Borrelia burgdorferi sensu stricto (Bbss), the etiological agent of LD in the United States. . Lizard-feeding by southeastern I. scapularis may tend to suppress sylvatic cycles of B. burgdorferi, and thus may be an important reason why LD case rates in the Southeast are much lower than in the Northeast and upper Midwest. Nevertheless, some skinks …

Identification Of Chemotherapeutic Agents Against Leishmaniasis And Chagas' Disease, Miguel Abran Vasquez

Open Access Theses & Dissertations

Patients with clinical manifestations of leishmaniasis and Chagas' disease rely on few drugs that have limited efficacy and considerable side effects. Expanding the diversity of available chemotherapeutic drugs for these diseases is of extreme medical importance. Enones or á,í¢-unsaturated ketones, initially developed as anti-cancer agents, are a worthy of class of compounds to test for activity against Leishmania major and Trypanosoma cruzi as these eukaryotic parasites share many of the characteristics exhibited by cancer cells. The anti-parasitic activity of a library of á,í¢-unsaturated ketones (136 derivatives) was screened against L. major as well as in mammalian cells. Three compounds (NC901, …

Ruthenium-Azole Complexes As Chemotherapeutic Agents Against Leishmaniasis, Eva Iniguez

Open Access Theses & Dissertations

Leishmaniasis is a neglected disease that affects millions of people worldwide. Poor efficacy and high toxicity of the limited treatment options demonstrate the need for the development of new chemotherapeutic agents to treat this disease. In order to respond this concern, the development of novel Ru-azole complexes as chemotherapeutic agents by inhibiting the cytochrome P-450 dependent C14-α-demethylation of lanosterol to ergosterol which is essential for the parasite survival. In addition, Ruthenium would enhance the activity of the parental drug, by helping ketoconazole/clotrimazole to cross the parasite membrane, together presenting low toxicity. The viability and citotoxicity of the Ru-azole compunds was …

The Effect Of Exogenous Leptin On Dendritic Cell Migration And Interactions With T Cells, Amanda L. Gonzales

Open Access Theses & Dissertations

Obesity is a complex, chronic disease that has reached epidemic proportions in the United States and shows no indication of receding. It is a state of chronic low-grade inflammation that is initiated by morphological changes in large accumulations of adipose tissue. Leptin is a pleiotropic hormone secreted by adipose tissue, presenting a possible link between obesity and inflammation. In this study, we assessed the effect of leptin on bone marrow-derived (BM) dendritic cells (DC) (BM-DC) function, antigen presenting cells vital for the activation of naí¯ve T cells. Previous data produced in our laboratory established that the addition of leptin to …

Equine Serum Antibody Responses To Streptococcus Equi And Streptococcus Zooepidemicus, Rafaela De Negri

Theses and Dissertations--Veterinary Science

Streptococcus zooepidemicus (Sz) and Streptococcus equi (Se) share 98% DNA sequence homology, but display different pathogenic properties. Infection by one organism does not cross-protect against the other. To better understand pathogenic differences between these organisms and gain information about which proteins are expressed in horses infected experimentally with Se, intrauterine Sz or naturally with respiratory Sz we compared antibody specificities of convalescent sera using ELISA. These comparisons were based on sets of 8 and 14 immunoreactive recombinant proteins of Se strain CF32 and Sz strain NC78, respectively. Sera from donkeys that were previously naturally affected with strangles and later developed …

Understanding Amphibian Decline: The Role Of Pesticides And The Pathogenic Chytrid Fungus On Amphibians And Aquatic Communities, Taegan A. Mcmahon

USF Tampa Graduate Theses and Dissertations

Amphibians are the most threatened taxon on the planet. Declines have been associated with over-exploitation, habitat loss, pollution, and pathogenic diseases, but of these factors, pollution and disease have been relatively under-studied. Here, I investigated: 1) the impacts of commonly used pesticides on aquatic communities, 2) the effect of these pesticides on amphibian susceptibility to the pathogenic chytrid fungus, Batrachochytrium dendrobatidis (Bd), and 3) whether there are non-amphibian hosts of Bd and 4) how to best quantify the survival of Bd through ontogeny of the host.

In my first research chapter, I quantified the effects of environmentally relevant concentrations of …

Innate Immune Responses To Respiratory Syncytial Virus: Age-Associated Changes, Terianne Maiko Wong

USF Tampa Graduate Theses and Dissertations

Respiratory syncytial virus (RSV) infection causes ~64 million cases of respiratory disease and 200,000 deaths annually worldwide, yet there is no broadly effective prophylactic or treatment regimen. RSV can produce acute respiratory illness in patients of all ages but strikes the age extremes, infants and the elderly, with highest frequency presumably due to innate immune deficiencies. A higher morbidity and mortality has been reported for the elderly above 65 years of age, which has been attributed to immune senescence. Efforts to generate an effective vaccine have thus far been unsuccessful.

The innate immune system provides the first line of defense …

Neutralizing Antibodies Against The Ricin Toxin Binding Subunit (Rtb), Anastasiya Yermakova

Legacy Theses & Dissertations (2009 - 2024)

Ricin is a toxin that is naturally produced by the seeds of the castor bean plant Ricinus communis, and is part of a family of A-B toxins that includes Shiga, cholera, and anthrax toxins. The toxin consists of two subunits, RTA and RTB, which are linked by a disulfide bond. RTA is an RNA N-glycosidase that selectively targets and inactivates 28S ribosomal RNA, thereby arresting protein synthesis and leading to cell death. RTB is a galactose/ N-acetylgalactosamine-specific lectin that mediates attachment, entry, and intracellular trafficking of ricin in host cells. Currently, there is no approved vaccine or therapeutics available against …