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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Genotyping of multidrug-resistant strains of mycobacterium tuberculosis in the Limpopo Province

Kgasha, Matete Olga 2013 (has links)
Genotyping of TB is essential to investigate and confirm transmission of the multi-drug resistant tuberculosis and of great value in optimizing strategies for the determination of strains causing the increased mortality rates of TB outbreaks. Sputum samples (207) were collected from National Health Laboratory Services in Polokwane laboratory for determining mutations and genotypes of the Mycobacterium tuberculosis strains using GenoType®MTBDRplus (Hain LifeScience, Germany) and Real-Time PCR (Roche, South Africa) techniques. Of the 207 samples, 28 (13.5%) exhibited drug resistance. Thirteen of the 28 (46%) MDR-TB strains belonged to the non-Beijing family, with mutations at codons rpoB 516 and rpoB 526 for RIF and katG 315 and inhA 15 for INH resistance. The Non-Beijing strains 75% (21/28) were monoresistant to RIF 14% (3/21) at codons 516, 526, 531 of rpoB gene and INH 19% (4/21) at codon 315 of katG and codon 15 of inhA 5% (1/21). Of the eight Beijing strains, 3(8%) were INH- resistant at codon 315 for katG and codon 15 for inhA and 3(8%) were RIF-resistant with mutations at codons 516 and 526. Two samples were typed as MDR for the Beijing strains with codon 315 for INH and codons 526 and 531 for RIF. The sample with a co-infection for Beijing and non-Beijing was an MDR-TB strain with mutations in rpoB codons 526, 531, katG 315 and inhA 8, 15 and16. The study showed a high rate of drug resistance with the non-Beijing compared to Beijing strains and mutations in specific codons for RIF and INH are variable for the TB families. Thesis (M.Sc. (Medical Microbiology)) --University Limpopo, 2013
2

Factors affecting treatment outcomes in tuberculosis (TB) patients in the Limpopo Province, South Africa

Gafar, Mohammed Mergni 2013 (has links)
Tuberculosis (TB) threatens the public health all over the world. South Africa is ranked fifth on the list of 22 high burden countries. SA has not achieved the international targets for cure rate and default rate yet. This is attributed to high HIV/AIDS prevalence and emergence of multi- drug resistant TB. Limpopo Province experiences poor TB treatment outcome, in spite of the adoption of strategies that proved globally that they can improve the outcome. The factors affecting treatment outcome in Limpopo Province are as yet undocumented. The specific objectives of this study were to determine the demographic profile of TB patients in the Limpopo Province; to investigate the treatment outcomes and to establish the relationship between age, gender, HIV status, treatment regimen and health facility level and the treatment outcomes in patients diagnosed with pulmonaryTB for period between 2006- 2010, inclusive, in Limpopo Province. Method Retrospective data for the period between 2006 and 2010 (inclusive) were reviewed, and 1200 records of cases of confirmed TB patients were sampled from the ETR.net provincial database. All these patients were diagnosed and treated according to guidelines adopted by the national TB control programme. Standard WHO definitions were used to classify the TB treatment outcome. Chi squire test was used to investigate the association between age, gender, diagnostic category and treatment regimen and treatment outcome. Results Of the 1200 TB cases sampled, 656 (54%) were male. Most of them fell within the age group 22- 55 years (n=871; 72.5%)). According to diagnostic category, 1035 (86.2%) were new cases; 962 (80.1%) cases received regimen I (two months of rifampicin [R], isoniazid [H], pyrazinamide [Z} and ethambutol [E] followed by four months of rifampicin and isoniazid, 2RHZE+ 4RH); 893 (74.4%) cases had successful treatment; 118 (9.8%) defaulted on treatment; 26 (2.2%) had treatment failure, and 163 (13.6%) died. There was a strong association between age (P <0.001), diagnostic category (P < 0.001), treatment regimen (P < 0.001), and health facility level (P< 0.001) and treatment outcome. The success treatment was highly significant (P <0.001) for the cases that fell within the age group 3- 6 years, those that were diagnosed as new cases, those that received treatment at mine health facilities or were treated with regimen III (2RHZ + 4RH). While the default rate was highly significant (P< 0.05) for the cases aged 7- 12 or 22- 55 years, patients that had history of defaulting, and those that received treatment at a community health centre or village health facilities – treatment failure was highly significant (P< .05) for Those fell within age group 22-55 or 56- 74 years, those had initial treatment failure, those that received treatment at hospital or mobile health facilities or treated with regimen II (3RHZES + 5RH) while the death rate was highly significant (P< 0.05) for the cases either fall within age group 0-2, 22- 55 or 56- 74 years, had initial failure, received treatment at hospital or village health facilities or treated with regimen). The un success rate was very highly significant (P< 0.001) for those either characterized by; fall within age group 22- 55 years, had initial failure, received treatment at hospital or village health facilities or treated with regimen II. Conclusion TB treatment outcome are poor in the Limpopo Province, particularly among patients with previous history of TB treatment, those receiving treatment in hospitals, or those being treated with first line regimen II. This situation requires that the TB control programme and other relevant programmes be strengthened, for instance through integration at facility level, towards more effective response to the challenges which hamper progress towards international targets on TB. Further studies are needed to address the effect of HIV status and AIDS, CD4+ cell counts, anti-retroviral therapy (ART), cotrimoxazole preventive therapy (CPT) and radiological presentation, and their effect on TB treatment outcome in Limpopo Province. Those data are not routinely captured on ETR.net, hence were not included in the present study. Thesis (M.Pharm.) --University of Limpopo, 2013
3

SYNTHESIS OF NOVEL AZIRIDINE DERIVATIVES OF PODOCARPIC ACID

Rhoden, Stephen 1 January 2007 (has links)
Podocarpic acid (a diterpenoid resin acid extracted from the Podocarpacea specie of plants) has shown cytotoxicity against carcinoma of the nasopharynx. Since this discovery has been made, research has been performed in order to alter the structure of the resin acid so as to increase the anticancer activity. The carboxylic acid and phenol functional groups, which are present in podocarpic acid, make it possible to synthesize new derivatives selectively at the C-15, C-13, and C-7 positions as well as by substitution of the phenol hydroxyl group. Thus numerous derivatives can be prepared, in high yield, for the purpose of investigating their potential, as new drug leads for the treatment of cancer. In this study, Doyle's catalyst (Dirhodium tetrakis caprolactamate) was used to form a novel derivative in high yield (85%) which contained a 3-membered aziridine ring at the C-6 and C-7 position. The main thrust of this research involved the formation a series of novel derivatives of the aziridine compound by utilizing phenol and m-chlorophenol as nucleophiles to open the aziridine ring. These novel compounds will now be sent to the National Institute of Health (NIH) for bioassay against 60 human cancer cell lines. M.S. Department of Chemistry Sciences Industrial Chemistry MS
4

The occurrence and molecular characterization of non-tuberculous mycobacteria in cattle, African buffalo (syncerus caffer) and their environments in South Africa and genomic characterization and proteomic comparison with mycobacterium bovis

Gcebe, Nomakorinte 2015 (has links)
The aim of this study was to investigate the diversity and prevalence of non-tuberculous mycobacteria (NTM) in cattle, African buffaloes and their environments in South Africa and the potential of these NTM to elicit cross- reactive immune responses in these animal species which may in turn lead to false diagnosis of bovine tuberculosis. A total of 40 NTM species were identified during a countrywide survey. Mycobacterium terrae, Mycobacterium nonchromogenicum, Mycobacterium vaccae/ Mycobacterium vanbaalenii and a group of isolates closely related to Mycobacterium moriokaense (M. moriokaense-like isolates) were the four most frequently isolated species. Further characterization of M. moriokaense- like isolates revealed two novel NTM species which were named Mycobacterium malmesburii sp.nov. and Mycobacterium komanii sp.nov. respectively. Genomes of M. nonchromogenicum, M. malmesburii sp. nov., M. komanii sp. nov., and M. fortuitum ATCC 6841 were elucidated and investigated for genes encoding homologues of M. bovis predominant immunogenic proteins. These included genes encoding for the Esx family proteins (esx genes), mpb70, mpb63, mpb64, hspX, tpx, Rv1120c, canA and dnaK. The esx gene orthologs encoded in ESX-1 (esxA and esxB), ESX-3 (esxH and esxG), esxR, and ESX-4 (esxT and esxU) loci were identified in the NTM genomes while those encoded in ESX-2 locus were absent in all the four NTM genomes and only esxN (encoded in the ESX-5 locus) and its homologue, esxK were present in M. nonchromogenicum. Gene orthologs encoding for MPB70 (M. malmesburii sp.nov. and M. komanii sp.nov.), DnaK (all four NTM species), CanA (all four NTM species), MPB64 (all four NTM species), Rv1120c (in all four NTM species), TpX, MBP63 and HspX (all in M. nonchromogenicum and M. fortuitum), were found in the NTM genomes. In contrast orthologs of mpb83 and espC were not detected in any of the four NTM. We could not judge just based on the overall protein sequence homologies of the antigens whether the NTM homologues will give rise to cross-reactive immune responses. We consequently checked the existence in NTM of epitopes shown to be immunogenic in M. bovis and M. tuberculosis. Amino acid sequence alignment of the EsxA and EsxB of the NTM sequenced in this study as well as M. smegmatis, M. bovis and M. tuberculosis respectively was done to investigate their similarities at “immunogenic” epitope level. In this analysis, we found that the six bovine T-cell recognized epitopes of M. bovis ESAT-6 described by Vordermeier et al., 2003 and 2007 had similarities to those of M. fortuitum and M. nonchromogenicum (showing sequence similarity of as high as 81.28% and as low as 52.9% ). Likewise a certain degree of sequence similarity between the six M. bovis CFP 10 immunogenic epitopes and those of the NTM species (highest similarity of 75% observed between all NTM and M. bovis and lowest similarity of 50% between M. komanii sp.nov, M. malmesburii sp.nov and M. bovis.) was observed. Still, with sequence homologies of less than 100% between the M. bovis immunogenic epitopes and those of the NTM, it was difficult to unambiguously predict T-cell cross-recognition. Comparison of the EsxR and EsxH amino acid sequences at immunogenic epitope level, revealed higher sequence similarities in the epitopes of NTM and those of M. bovis than the predicted protein sequences of EsxA and EsxB. A sequence similarity of 100% was observed between two of the five M. bovis immunogenic epitopes of EsxR and those of M. fortuitum, M. malmesburii sp. nov. and M. komanii sp.nov. Full cross- recognition of these NTM EsxR epitopes is therefore highly likely, and may lead to misdiagnosis of bovine Tuberculosis (BTB). The other three EsxR/EsxH epitopes shown to be immunogenic in M. bovis also exist in the three NTM showing similarity of as low as 77.7%. Thesis (PhD)--University of Pretoria, 2015. WOTRO Science for Global Development Genomics Research Institute (GRI) Veterinary Tropical Diseases PhD Unrestricted
5

A enfermeira ananéri no país do futuro

Barreira, Ieda de Alencar. 1996 (has links)
Thesis (Doutorado em Enfermagem)--Universidade Federal do Rio de Janeiro. Escola de Enfermagem Anna Nery, 1992. Includes bibliographical references (p. 356-363).
6

A enfermeira ananéri no país do futuro

Barreira, Ieda de Alencar. 1996 (has links)
Thesis (Doutorado em Enfermagem)--Universidade Federal do Rio de Janeiro. Escola de Enfermagem Anna Nery, 1992. Includes bibliographical references (p. 356-363).
7

A Multiscale Modeling Study of Iron Homeostasis in Mycrobacterium Tuberculosis

Ghosh, Soma 2014 (has links) (PDF)
Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis (TB), has remained the largest killer among infectious diseases for over a century. The increasing emergence of drug resistant varieties such as the multidrug resistant (MDR) and extremely drug resistant (XDR) strains are only increasing the global burden of the disease. Available statistics indicate that nearly one-third of the world’s population is infected, where the bacteria remains in the latent state but can reactivate into an actively growing stage to cause disease when the individual is immunocompromised. It is thus immensely important to rethink newer strategies for containing and combating the spread of this disease. Extraction of iron from the host cell is one of the many factors that enable the bacterium to survive in the harsh environments of the host macrophages and promote tuberculosis. Host–pathogen interactions can be interpreted as the battle of two systems, each aiming to overcome the other. From the host’s perspective, iron is essential for diverse processes such as oxygen transport, repression, detoxification and DNA synthesis. Infact, during infection, both the host and the pathogen are known to fight for the available iron, thereby influencing the outcome of the infection. It is of no surprise therefore, that many studies have investigated several components of the iron regulatory machinery of M.tb and the host. However, very few attempts have been made to study the interactions between these components and how such interactions lead to a better adapted phenotype. Such studies require exploration at multiple levels of structural and functional complexity, thereby necessitating the use of a multiscale approach. Systems biology adopts an integrated approach to study and understand the function of biological systems. It involves building large scale models based on individual biochemical interactions, followed by model validation and predictions of the system’s response to perturbations, such as a gene knock-out or exposure to drug. In multiscale modeling, an approach employed in this thesis, a particular biological phenomenon is studied at different spatiotemporal levels. Studying responses at multiple scales provides a broader picture of the communications that occur between a host and pathogen. Moreover, such an analysis also provides valuable insights into how perturbation at a particular level can elicit responses at another level and help in the identification of crucial inter-level communications that can possibly be hindered or activated for a desired physiological outcome. The broad objectives of this thesis was to obtain a comprehensive in silico understanding of mycobacterial iron homeostasis and metabolism, the influence of iron on host-pathogen interactions, identification of key players that mediate such interactions, determination of the molecular consequences of inhibiting the key players and finally the global response of M.tb to altered iron concentration. Perturbation of iron homeostasis holds a strong therapeutic potential, given its essentiality in both the host and the pathogen. Understanding the workings of iron metabolism and regulation in M.tb has been a main objective, so as to ultimately obtain insights about specific therapeutic strategies that capitalize on the criticality of iron concentration. An in-depth study of iron metabolism and regulation is performed at different levels of temporal and spatial scales using diverse methods, each appropriate to investigate biological events associated with the different scales. The specific investigations carried out in the thesis are as follows, a) Reconstruction of a host-pathogen interaction (HPI) model, with focus on iron homeostasis. This study represented the inter-cellular level analysis and was crucial for the identification of key players that mediate communication between the host and pathogen. Additionally, the model also provided a mathematical framework to study the effect of perturbations and gene knock-outs. b) Understanding the influence of iron on IdeR, an iron-responsive transcription factor, also identified as a key player in the HPI model. The study was carried out at the molecular level to identify atomistic details of how IdeR senses iron and the resulting structural modifications, which finally enables IdeR-DNA interaction. The study enabled identification of residues for the functioning of IdeR. c) Genome scale identification of genes that are regulated by IdeR to obtain an overview of the various biological processes affected by changing iron concentrations and IdeR mutation in M.tb. d) To understand the direct and indirect influences of iron and IdeR on the M.tb proteome using large scale protein-protein interaction network. The study enabled identification of highest differentially regulated genes and altered activity of the different biological processes under differing iron concentrations and regulation. e) Systems level analysis of the M.tb metabolome to investigate the metabolic re-adjustments undertaken by M.tb to adapt to altered iron concentration and regulation. The conceptual details and the background of each of the methods used to study the specific aims are provided in the Methodology chapter (Chapter 2). Construction of the host-pathogen interaction (HPI) model and the insights obtained from this study are presented in Chapter 3. A rule based HPI model was built with a focus on the iron regulatory mechanisms in both the host and pathogen. The model consisted of 194 rules, of which 4 rules represented interactions between the host and pathogen. The model not only represented an overview of iron metabolism but also allowed prediction of critical interaction that had the potential to form bottleneck in the system so as to control bacterial proliferation. Infact, model simulation led to the identification of 5 bottlenecks or chokepoints in the system, which if perturbed, could successfully interfere with the host-pathogen dynamics in favour of the host. The model also provided a framework to test perturbation strategies based on the bottlenecks. The study also established the importance of an iron responsive transcription factor, IdeR for regulating iron concentration in the pathogen and mediating host-pathogen interactions. Additionally, the importance of mycobactin and transferrin as key molecular players, involved in host-pathogen dynamics was also determined. The model provided a mathematical framework to test TB pathogenesis and provided significant insights about key molecular players and perturbation strategies that can be used to enhance therapeutic strategies. Given the importance of IdeR in HPI, its molecular mechanism of activation and dimerization was explored in Chapter 4. The main objective of the study was to explore the structural details of IdeR and its iron sensing capacity at the molecular level. A combination of molecular dynamics and protein structure network (PSN) were used to analyse IdeR monomers and dimers in the presence and absence of iron. PSNs used in this thesis are based on non-covalent interactions between sidechain atoms and are quite efficient in identifying iron induced subtle conformational variations. The study distinctly indicated the role of iron in IdeR stability. Further, it was observed that IdeR monomers can take up two major conformations, the ‘open’ and ‘close’ conformation with the iron bound structure preferring the ‘close’ conformation. Major structural changes, such as the N-terminal folding and increased propensity for dimerization were observed upon iron binding. Interestingly, careful analysis of structure suggests a role of these structural modifications towards DNA binding and has been tested in the next chapter. Overall, the results clearly highlight the influence of iron on IdeR activation and dimerization. The predisposition of IdeR to bind to DNA in the presence of metal is clearly visible even when the simulations are performed solely on protein molecules. However, to confirm the conjectures proposed in this chapter and to obtain the atomistic details of IdeR-DNA interactions, the IdeR-DNA complex was investigated. Chapter 5 focuses on the mechanistic details of IdeR-DNA interactions and the influence of iron on the same. IdeR is known to bind to a specific stretch of DNA, known as the ‘iron-box’ motif to form a dimer-of-dimer complex. Molecular dynamics followed by protein-DNA bipartite network analysis was performed on a set of four IdeR-DNA complexes to obtain a molecular level understanding of IdeR-DNA interactions. A striking observation was the dissociation of IdeR-DNA complex in the absence of iron, undoubtedly establishing the importance of iron for IdeR-DNA binding. At the residue level, hydrogen bond and non-covalent interactions clearly established the importance of N-terminal residues for DNA binding, thereby confirming the conjecture put forth in the previous chapter. An important aspect studied in this chapter is the allosteric nature of IdeR-DNA binding. Recent years have witnessed a paradigm shift in the understanding of allostery. Unlike the classical definition of allostery that was based on static structures, the newer definition is based on the conformational ensemble as represented by the shift in the energy landscape of the protein. The allosteric nature of IdeR-DNA complex was probed using simulated trajectories and indeed they suggest iron to be an allosteric regulator of the protein. Finally, based on the known experimental data and observations presented in Chapters 4 and 5, a multi-step model of IdeR activation and DNA binding has been proposed. In chapter 6, a global perspective of IdeR regulation in M.tb was obtained. This was important to gain insights about the influences of iron and its regulation at the M.tb cellular level. A genome scale identification of all possible IdeR targets based on the presence of ‘iron-box’ motif in the promoter region of the genes was carried out. An interesting aspect of this study was the use of energetic information from previous molecular dynamics study as an input for generation of the motif. A total of 255 such IdeR targets were identified and converted into an IdeR target network (IdeRnet). Along with IdeRnet, an unbiased systems level protein-protein interaction network was also generated. To study the response of the pathogen to external perturbations, iron-specific gene expression data was integrated into the network as node weights and edge weights. Analysis of IdeRnet provides interesting associations between fatty acid metabolism and IdeR regulations. Specific genes such as fadD32, DesA3 or lppW have been found to be affected by IdeR mutation. While IdeRnet discusses the direct associations, the global level responses are monitored by analysing pathways for the flow of information in the protein-protein interaction network (PPInet). Comparisons of the PPInets under conditions such as altering iron concentrations and lack of iron homeostasis led to the identification of the ‘top-most’ active paths under the different conditions. The study clearly suggests a halt in the protein synthesis machinery and decreased energy consumption under iron scarcity and an uninhibited consumption of energy when iron homeostasis is perturbed. In the final chapter (Chapter 7), flux balance analyses has been used to investigate the influence of iron on M.tb metabolism. The importance of iron for metabolic enzymes has already been established in the previous chapter. Additionally, M.tb is known to produce siderophores, an important metabolite that requires amino acids as its precursors, for iron extraction. All this, together highlighted the importance of iron and its regulation of M.tb metabolism. Flux balance analysis has been used previously to study the metabolic alterations that occur in an organism under different conditions. For this study, iron specific gene expression data was also incorporated into the model as reaction bounds and the flux values so obtained were compared in different environmental conditions. The study provided valuable insights into the metabolic adjustments taken up by M.tb under iron stress conditions and correlates well with the responses observed from the interactome as well as experimental observations. Most significantly, changes were observed in the energy preferences of the cell. For instance, it was noted that while the wild type strain of M.tb prefers synthesis of ATP via glycolysis, the IdeR mutant strain preferred oxidative phosphorylation. The picture becomes clearer when one accounts for the uncontrolled utilization of energy and rapid activation of protein synthesis machinery in the IdeR mutant strain. Biological systems are inherently multiscale in nature and therefore for a successful drug target regime, analysis of the genome to the phenome, which captures interactions at multiple levels, is essential. In this thesis, a detailed understanding of iron homeostasis and regulation in M.tb at multiple levels has been attempted. More importantly, insights obtained from one level, formed questions in the next level. The study was initiated at the inter-cellular level, where the influence of iron on HPI was modeled and analysed. From this study, IdeR, an iron-responsive transcription factor was identified as a key player that had the potential to alter host-pathogen interactions in the favour of the host. For a complete understanding of how IdeR regulates iron homeostasis, it was imperative to obtain a molecular level insight of its mechanism of action. Finally, the various aspects of IdeR regulation were investigated at the cellular level by analysing direct and indirect influences of IdeR on M.tb proteome and metabolome. The study suggests certain therapeutic interventions, such as 1) reduction in the concentration of free transferrin various, 2) mutations at the N-terminal sites of IdeR, 3) regulation of proteins involved in production of mycolic acids by iron and 4) perturbation of altering energy sources, which capitalize on iron and should be investigated in detail. In summary, the consequences of iron on TB infection were studied by threading different levels. This is based on the belief that most biological functions involve multiple spatio-temporal levels with frequent cross talks between the different levels, thereby making such multiscale approaches very useful.

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