Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

Magister Public Health - MPH / Tuberculosis (TB) is a major health problem worldwide, with an estimated 9 million new cases accounting for an estimated 1.5 million deaths in 2012. Non-compliance with TB treatment has become a major barrier to achieving global TB control targets. Namibia is one of the worst affected countries in Africa with a high case notification rate (CNR) of all forms of TB and relatively low treatment success rate compared to the WHO targets. The study aimed at investigating TB treatment compliance and measuring its association to patient characteristics and treatment outcomes, in determining the effects of compliance on treatment outcomes in Windhoek District. This information is crucial for TB programme management and development of targeted strategies. A quantitative observational analytic study using a retrospective cohort design was adopted. New adult Pulmonary Tuberculosis (PTB) patients treated under DOTS in Windhoek District between 1st January 2013 and 31st December 2013 were included in the study based on specified criteria. Data was collected from the patients TB treatment cards using an extraction tool. Selection and information bias was eliminated by using clearly defined inclusion and exclusion criteria using a pre-tested standardised tool. Statistical analysis using descriptive and analytic statistics was done using Epi Info 7 to determine compliance, treatment outcomes and to measure the associations. Overall treatment compliance (89%), initial phase compliance (97.2%) and continuation phase compliance (88.1%) were reported in the study. Age (OR=4.3 95% CI (1.72 – 9.90), p-value=<0.01) and type of area (OR=0.02 95% CI (1.00 – 1.13), p-value=0.05) were associated with compliance in the continuation phase. Overall, type of area (OR=0.03 95% CI (0.00 – 0.91), p-value=0.04) remains associated with treatment compliance. Treatment success is reported among 86.1% of patients. Poor treatment outcomes are associated with non-compliance in the initial phase ( =49.98, p-value=<0.01), continuation phase ( =98.81, p-value=<0.01) and overall ( =110.02, p-value=<0.01). Overall treatment compliance (89%) although higher than expected was lower than the WHO recommended 90% compliance. Very high compliance (97.2%) were reported in the initial phase of treatment whilst compliance was also lower than desired (88.1%) in the continuation phase. Non-compliance recorded in the continuation phase is in agreement with the literature. Age and type of area are associated with compliance as reported in the continuation phase and overall in this study is new contribution of knowledge. The findings suggest that treatment compliance is associated with treatment success in both phases of treatment and overall. Low compliance especially in the continuation phase could lead to poor treatment outcomes such as prolonged infections, relapse, high TB mortality and drug resistance leading to increased programme costs. The study concludes that non-compliance results in poor treatment outcomes highlighting the need for interventions that address compliance in all phases but specifically within the continuation phase and amongst those at risk of having reduced compliance such as those in rural areas and young adult patients aged (15 – 34 years). Recommendations to the District Management Team and TB Programme Managers include: identification of measures that promote treatment compliance; support and monitoring of TB patients’ compliance continuously; strengthening CB-DOT by increasing CB-DOT points and enhancing CB-DOT supporters’ capacity as well as strengthening record keeping as a monitoring tool to increase compliance and improve treatment outcomes.

Background: A post-exposure regrowth model utilizing the well-tried Bactec radiometric system, which would simulate in vivo situations at the site of invasive disease, was developed to measure drug activity against multiplying Mycobacterium tuberculosis. Aims: The aims of this dissertation were to (a) construct a radiometric model simulating drug efficacy relating to the combined bactericidal activity and delays in regrowth due to the action of anti¬tuberculosis (TB) agents, (b) compare the killing kinetics of drugs singly and in combinations by the time-kill curve method, with the radiometrically-determined regrowth model, and (c) assess whether the Bactec radiometric regrowth model could predict likely bactericidal activities of drugs. Design and methods: Drug concentrations in the time-kill curve method were in a range of achievable drug concentrations at the site of infection and in multiples of the minimal inhibitory concentration (MIC), (1x, 2x or 3x, and 8x). Exposure times of 6h, 24h, 48h and 72h were used and these were based on pharmacokinetic data reflecting likely periods of in vivo exposure in TB lesions. Standardized inocula of approximately 106CFU/mi of actively multiplying M. tuberculosis strains were used. The same concentrations, exposure times and bacterial concentrations were used for the assessment of radiometrically-determined post-exposure regrowth times of M. tuberculosis. Growth times were recorded as the number of days required to reach a predetermined growth index (GI) level in the Bactec system, and were expressed as T400 readings in days. Simple linear regression and a mathematical logistic model were used to assess whether the radiometric post-exposure regrowth model could predict the bactericidal activity of the drugs. For drug combination studies, 1MIC of isoniazid (INH) and rifampicin (RMP) were used singly and in combination while 2MIC of ethambutol (EMB), streptomycin (SM), ofloxacin (OFL) and amikacin (AMK) were used in combinations studies. Colony counts at Oh and following 24h exposures were performed and regrowth patterns were determined using the T400 method. M. tuberculosis H37Rv was tested and subsequently resistant strains. Results: INH and RMP were highly bactericidal while EMS showed moderate activity in the time-kill curve method. The three drugs produced the best curves, showing longer regrowth times and markedly depressed rates of regrowth in the Sactec post-exposure regrowth model. Using simple linear regression, a linear relationship between bacterial survivors and the radiometric regrowth times, T400, was achieved for all drugs tested. Even better agreement was found when control-related regrowth times, (T-C) 400, were used in the analysis. Conditions compromising the linear relationsbip in the radiometric regrowth model, for OFL and less markedly EMS and AMK, were likely postantibiotic effects (PAEs) brought on by the short exposure time (6h), and drug carry-over effects due to concentrations ≥ 8 MIC for INH, RMP and 8M (10x and 20x MICs). The mathematical logistic model showed good correlation between bactericidal activity and regrowth for INH and RMP but not for EMB, SM, OFL and AMK. Drug combination effects in the two techniques depended on the criteria used to describe synergy. Generally, it was found in drug combination experiments that the drugs did not influence each other to a meaningful extent. Discussion and conclusions: For prediction of bactericidal activity, interpretation of the radiometrically-determined regrowth model needs to accommodate PAEs and the effect of subinhibitory concentrations. The validity of the mathematical logistic model is not clear. Technical aspects of future studies such as better organism dispersal, need to be improved to achieve a more reliable evaluation based on the logistic model. For drug combination studies, the radiometric regrowth model yielded findings that were difficult to interpret in relation to published data, reinforcing the need for the use of internationally standardized techniques which would give statistically reliable data. The radiometrically-determined regrowth model showed good discrimination between the standard activities of anti- TB agents, correlating with clinical efficacy. It is simple to perform and could prove to be useful for the screening of candidate anti- TB drugs. Improved technical stringency and the evaluation of poorly active control drugs, are however needed before proof of validity of the model can be established. / Dissertation (MSc (Medical Microbiology))--University of Pretoria, 2007. / Medical Microbiology / unrestricted

Using a mechanism-based approach to drug discovery, efforts have been directed towards developing novel ATP mimics that can act as GS inhibitors. The purine-based systems, adenosine, adenine and allopurinol, were identified as possible scaffolds for potential ATP mimics, while various meta-disubstituted benzenoid compounds, 3-aminobenzonitrile, 3-aminophenol, resorcinol, 3-aminobenzyl alcohol, 3-hydroxybenzoic acid and 3-aminobenzoic acid have been explored as adenine analogues. These compounds were treated with different alkylating and acylating agents. Allylation of all the substrates was achieved using allyl bromide and N-9 alkylation of protected allopurinol was effected using a number of specially prepared Baylis-Hillman adducts. Acylation of the benzenoid precursors with chloroacetyl chloride, acetoxyacetyl chloride, acryloyl chloride and specially prepared 2,3,4,5,6-pentaacetylgluconoyl chloride afforded the corresponding mono- and /or diacylated products in varying yields (4-96%). Elaboration of the alkylated and acylated products has involved the reaction of hydroxy systems with diethyl chloro phosphate and chloro derivatives with triethyl phosphite in Arbuzov-type reactions to afford phosphorylated products. In all cases, products were fully characterized using 1- and 2-D NMR analysis and, where appropriate, high-resolution mass spectrometry. The application of Modgraph and ChemWindow NMR prediction programmes has been explored and the resulting data have been compared with experimental chemical shift assignments to confirm chemical structures and, in some cases, to establish the position of allylation or acylation. Experimental assignments were found to be generally comparable with the Modgraph data, but not always with the ChemWindow values. The docking of selected products in the 'active-site' of GS and their structural homology with ATP, both in their free and bound conformations have been studied using the ACCELERYS Cerius² platform. All the selected ATP mimics exhibit some form of interaction with the 'active-site' residues, and a number of them appear to be promising GS ligands.

Tuberculosis (TB) still remains a health problem globally with over a million new infections and a mortality rate of 1.5 million individuals annually (Hawn et al., 2014). The emerging multi-drug resistant (MDR) strains that accompany human immune deficiency virus (HIV) infection in high-incidence populations contribute significantly to the health burden of TB (Areeshi et al., 2014). The standard treatment that is advocated by the World Health Organization (WHO) for active tuberculosis includes long-term therapy that incorporates the use of isoniazid, rifampicin, pyrazinimide and ethambutol as front line drugs (WHO, 2013). Drug resistance against established treatment options for TB makes research into new forms of therapy an imperative in health care (Ntulela et al., 2009). South Africa is currently witnessing a high number of cases of drug-resistant TB. In some parts of the country, one in ten cases of TB is resistant to treatment. It is therefore essential to have new anti-tuberculosis agents, which can be readily and simply produced from some local source (Warner et al., 2014). A logical starting point for this research of new agents would be the herbal medicines which have been used for centuries in rural areas by local healers. Western developed countries have harvested ethno botanical knowledge and have produced drug therapies for conventional medicines for other ailments. The activity of extracts of the active plants and their properties still require study in animal models in order to assess their future as new anti-tuberculosis agents (Lall and Meyer, 1999). This study focuses on qualitative and quantitative experimental findings after the administration of a medicinal plant extract to animals. This will include daily observation of animals, recording of feed consumption, recording of animal weights, macroscopic examination of animals at necropsy, tissue harvesting, histological procedures and microscopy.

This dissertation consists of three essays, each covering very distinct topics under the broad umbrella of Development Economics, each set in a different region of the developing world (Latin America, Sub-Saharan Africa, and South Asia). The one element that loosely ties them together is that they each seek to add, in a small way, to our understanding of factors that contribute to, and in some cases may entrap people in, poverty: factors such as (lack of) geographic mobility, hunger, and disease. In the first chapter, I use the natural experiment of military conscription in Argentina, which randomly assigned not only military service, but also the location of service, to study the effect of this temporary displacement on long-run migration rates. I then use a rich source of administrative earnings and employment data to investigate the labor-market implications of conscription and, in particular, displacement. I find that conscription on the whole caused a small increase in the likelihood of appearing in the formal labor force, and a small increase in earnings particularly for those who were assigned to serve in the Navy. Assignment to military service outside of one's province of origin increased the likelihood of living outside the province of origin by 2.5 percent, and while the net effects of this displacement on earnings and employment are imprecisely estimated, the evidence suggests that there are modest long-term benefits of conscription in Argentina that are not fully attributable to displacement. In the second chapter, I investigate the effects of Ramadan on calorie consumption and labor supply among Muslim households in rural Malawi. Across four rounds of household survey data, I find no evidence of a decrease in calorie consumption during Ramadan on average. I do, however, find evidence that working-age people reduce their weekly work by about three hours, or nearly 20 percent, on average. This finding on calories shows substantial variation across the different rounds of data. The evidence presented calls into question the hypothesis that consumption during Ramadan should fall more dramatically when the holiday overlaps with the harvest (when baseline consumption levels are relatively high compared to the rest of the year), compared to when Ramadan falls near the annual hunger season (when baseline consumption levels tend to be much lower). I discuss potential implications of this variation for our understanding of seasonal consumption patterns. The third and final chapter, which is authored jointly with Kaivan Munshi and Nancy Luke, discusses a randomized intervention conducted in rural South India aimed at improving rates of treatment completion for tuberculosis. Tuberculosis (TB), despite being a highly treatable disease, kills well over 1 million people every year, with 95 percent of cases and deaths appearing in developing countries. India bears the largest TB burden of any country, with more than 25 percent of the world's total yearly cases. A key factor for successful management of TB is ensuring that patients complete the full six-month (or more) treatment regimen: missing even a few doses of the prescribed medications increases the likelihood of relapse and development of a drug-resistant strain of TB, which is much more difficult and costly to treat effectively. We conduct an intervention allowing patients to select a community member to serve as a Directly Observed Treatment (DOT) provider to help ensure compliance with the full treatment regimen. Although patients assigned a Community DOT provider report significantly more frequent visits and higher rates of satisfaction compared to our control group, we do not find any significant improvement in treatment outcomes among those assigned this intervention. We explore several potential explanations for this finding and suggest potential avenues for future research.

Microbiome research in the past decade has revealed an astounding prevalence of bacteria in various tissues in the human body. Concurrent progress in synthetic biology has generated a converging interest in the genetic programming of bacteria to locally produce therapeutic payloads and supplant physiological niches. This dissertation presents the development of bioengineering tools that address several key challenges for the clinical translation of therapeutic bacteria. In particular, we focus on the engineering of bacteria for tumor and granuloma applications. Bacteria have been demonstrated to selectively grow within solid tumors, primarily due to the reduced immune surveillance in the necrotic and hypoxic cores. This natural tropism to tumors presents a unique opportunity to engineer bacteria as drug delivery vehicles for cancer therapy. While the recent advancement in microbial engineering has constructed ranges of therapeutic bacteria, a universal bottleneck for clinical development is the lack of tools to rapidly characterize therapeutic candidates in a complex physiological environment. To recapitulate bacterial tumor colonization in vitro, we developed a method that selectively grows bacteria within the necrotic core of tumor spheroids. This platform enabled high-throughput cocultures and predicted in vivo therapeutic outcomes, identifying potent anticancer proteins deliverable by tumor-homing Salmonella typhimurium. To ensure safety when using bacteria that produce cytotoxic payloads, we prevented bacterial spread to unintended locations by confining bacterial growth in a tumor-specific environment. We constructed hypoxia, pH, and lactate sensors and regulated bacterial growth based on sensor activation. To improve tumor specificity, we engineered gene circuits to sense hypoxia and lactate in an AND-logic gate manner. Leveraging the coculture platform, we characterized sensor activities and circuit functionalities in tumor spheroids. This engineered strain showed improved tumor specificity in an animal tumor model. Moving towards clinical applications, a key challenge is to ensure bacterial delivery to tumors without activating adverse immune responses. Approaches such as surface decoration can evade immune systems, but static modification may result in bacterial overgrowth. We developed a genetically-encoded microbial encapsulation system with a tunable, dynamic expression of capsular polysaccharides. We constructed an inducible gene circuit to regulate encapsulation, which exhibited tunable protection of the probiotic Escherichia coli Nissle 1917 (EcN) from host immune factors. By dynamically balancing low immunogenicity and protection, transient encapsulation increased the maximum tolerated dose of bacteria by approximately 10-fold when systemically injected in vivo. This strategy enhanced antitumor efficacy in multiple tumor models. Building on our work of therapeutic bacteria for cancer, we explored the use of engineered bacteria to infiltrate other pathogenic regions in the body. Specifically, we discovered that probiotic EcN colonizes granulomas, pathological features that develop at infection sites including tuberculosis. Granulomas share key similarities with solid tumors, including hypoxia and necrosis, and pose significant challenges for delivering therapeutic agents to eradicate the pathogen Mycobacterium tuberculosis within. We engineered the probiotics to locally produce antimicrobial proteins against Mycobacterium within granulomas. We developed a novel dual lysis mechanism to simultaneously enhance therapeutic protein release and limit bacterial overgrowth. To improve specificity, we constructed hypoxia-dependent bacterial growth coupled with quorum-mediated gene activation. Finally, we showed that our engineered probiotics reduced levels of Mycobacterium strains. Altogether, the presented technologies utilize a multiscale framework from circuit design to in vitro and in vivo models and advance bacteria as next-generation drug delivery vehicles capable of sensing and responding to diseases in the body.

This quantitative, descriptive study investigated factors that contributed to TB patients registered in four Tembisa clinics in 2001, defaulting treatment. An interview schedule with closed and open-ended questions was used for 30 patients who could be traced who had interrupted treatment. The reasons for treatment interruption were related to socio-economic, TB policy-related and health care worker-related factors. The findings illustrate that TB management requires a multi-sectoral approach and joint efforts to tackle the disease that continues to kill people even though it is curable. / Health Studies / M.A. (Health Studies)

The study investigated the knowledge levels of clients on long-term tuberculosis (TB) treatment at Kwekwe General Hospital, Zimbabwe. A quantitative, descriptive research design was chosen and data was collected using a structured questionnaire with a convenience sample of 60 clients on TB treatment and 10 professional nurses. The major findings of the study were that although clients had some knowledge about their condition, there was a lack of knowledge regarding critical aspects such as information on drug-resistant TB and the Directly Observed Therapy Short Course. The professional nurses experienced constraints such as insufficient time for appropriate health education and home visits. Based on the study findings and conclusions, several recommendations were made. / Health Studies / Thesis(M.A(Health Studies))

no abstract available / Health Studies / M.A. (Health Studies)