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La capacidad de Mycobacterium tuberculosis para sobrevivir dentro del macrófago contribuye grandemente a su patogenicidad, latencia y persistencia durante la infección. Este bacilo induce alteraciones en el ambiente intrafagosomal e inhibe la maduración del fagosoma, favoreciendo su supervivencia intracelular. M. tuberculosis PknG secuestra al macrófago precisamente al evitar la fusión fagosoma-lisosoma. En este sentido, PknG representa una familia de dianas novedosas para enfrentar la necesidad de nuevos antimicrobianos para la tuberculosis latente. Aquí, apuntamos a: (i) elucidar la base estructural-molecular del ATP y Mg2+ como cofactores de PknG; (ii) caracterizar los parámetros cinéticos que gobiernan la formación del complejo PknG:ATP; e, (iii) identificar péptidos capaces de unirse a PknG para investigar experimentalmente su interactoma usando enfoques combinatorios como “Phage Display”. Nuestros resultados confirman que PknG se une exclusivamente al ATP con una constante de disociación (KD) de 108.8  22.9 µM. El Mg2+ estabiliza térmicamente a PknG de forma ATP-dependiente. Análisis de estado pre-estacionario muestran que la unión y disociación del ATP es rápida en el complejo PknG:ATP. Usando PknGN-Ext, TPR resolvimos la estructura cristalina en el estado unido al ADP mientras que demostramos que el ATP imposibilita la cristalización. Los análisis bioinformáticos de las librerías enriquecidas por Phage Display identificaron 57 potenciales peptidos que interactuarían con PknG. Una comparación cercana con el proteoma de M. tuberculosis proporcionó un subconjunto de 20 proteínas que podrían interactuar con PknG. Nuestros resultados confirmaron cinco proteínas asociadas a PknG previamente reportadas: PknG, DnaK chaperona, transportador ABC Rv1747, Proteína Ribosomal L23 y Factor de Elongación Tu, resaltando la validez de nuestra plataforma para descubrir el interactoma de PknG. Así, nuestros resultados revelan interacciones proteína-proteína putativas que podrían participar en la supervivencia micobacteriana, mientras que también proporcionan bases sólidas para desarrollar drogas antituberculosas al interrumpir estas interacciones o explotar estos peptidos tipo compuesto líder. / The ability of Mycobacterium tuberculosis to survive inside the macrophage greatly contributes to its pathogenicity, latency and persistence during infection. This bacillus induces alterations in the intraphagosomal environment and inhibits phagosome maturation, thus promoting mycobacterial survival. M. tuberculosis PknG hijacks the macrophage precisely by avoiding phagosome-lysosome fusion. In this sense, PknG represents a family of novel targets to cope with the need for new antimicrobials for latent tuberculosis. Here, we aimed to: (i) elucidate the structural-molecular basis of ATP and Mg2+ as PknG cofactors; (ii) characterize the kinetic parameters governing PknG:ATP complex formation; and, (iii) identify PknG-binding peptides to experimentally query PknG’s interactome using combinatorial approach such as Phage Display. Our results confirm that PknG exclusively binds to ATP with a dissociation constant (KD) of 108.8  22.9 µM. Mg2+ thermally stabilizes PknG in an ATP-dependent manner. Pre-steady-state analyses show that ATP binding and dissociation are rapid in the PknG:ATP complex. Using PknGN-Ext, TPR we solved the ADP-state crystal structure while showing that ATP precludes crystallization. Phage Display and bioinformatic analyses identified 57 potential PknG binders. A close comparison to the M. tuberculosis proteome provided a subset of 20 proteins that may interact with PknG. Our results confirmed five previously reported PknG-associated proteins: PknG, DnaK chaperone, ABC transporter Rv1747, Ribosomal Protein L23 and Elongation Factor Tu, highlighting our platform’s validity to uncover the PknG interactome. Altogether, our results reveal putative protein-protein interactions that may play a role in mycobacterial survival, while also providing solid bases for the development of anti-tuberculosis drugs by disrupting these interactions or exploiting these lead-like peptide molecules. / Tesis

Bovine tuberculosis (BTB) is a zoonotic disease that affects domestic and wild animals, and humans. It is caused by Mycobacterium bovis (M. bovis) and has a wide host range. The effective control of BTB is of paramount importance and this can be achieved through the use of accurate and comprehensive diagnostic tests. The most widely used methods to detect BTB are the skin test and in vitro gamma interferon assay which do not detect anergic animals, but serological tests such as ELISA and fluorescence polarization assay (FPA) have been found promising in ancilliary tuberculosis diagnosis. The overall aim was to study M. tuberculosis complex (MTBC) protein, mycobacterial protein bovis 70 (MPB70) as a target for serological assays in the detection of antibodies to bovine tuberculosis. The MPB70 protein was expressed, purified and labeled with fluorescein (FITC). The mpb70 gene was fragmented into three regions without disrupting predicted epitopes. The resulting protein Fragments were expressed as fusion proteins with the monster green fluorescent protein (MGFP). The recombinant MPB70 (rMPB70) and the expressed gene fragments 2&3 were tested in immunoblots and ELISAs. The rMPB70 and fragment 2-MGFP reacted with chicken antibodies raised against rMPB70 and immune sera from BTB infected buffaloes. MPB70 peptides were synthesized as an approach to identify even smaller antigenic regions. The peptides BT1G (residues 31-45) and BT51L (residues 81-95) were recognised by anti-MPB70 chicken antibodies in the ELISA and fall within fragment 1 and 2, respectively. The tracers (rMPB70-FITC, fragment 2-MGFP fusion and peptides BT1G&BT51L) were tested in the FPA, but the results failed to distinguish between immune sera from chickens immunized with rMPB70 and negative control sera. Even though the FPA was not successful, the MPB70 fragment 2-MGFP fusion protein, which was recognized by sera from BTB infected buffaloes, was tested in an ELISA using panels of sera from uninfected and naturally M. bovis infected buffaloes and cattle. The diagnostic performance of the ELISA was, however, overall unsatisfactory and hence of very limited use as a serological test to detect antibody responses to BTB as a stand-alone assay. Sera from some of the animals gave false positive reactions indicating that MPB70 was not sufficiently specific for serodiagnosis of M. tuberculosis complex infections. / Dissertation (MSc)--University of Pretoria, 2012. / Veterinary Tropical Diseases / unrestricted

Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2021 / Tuberculosis is one of the top 10 leading causes of death in the world. The development of drug resistant strains of Mycobacterium tuberculosis such as Multidrug resistant (MDR) and Extensively drug resistant (XDR) strains further complicate the TB control. Medicinal plants present a possible source for new potential antitubercular drugs. They have played an important role in drug discovery, with many pharmaceutical products originating from them. Isolation and characterisation of new antitubercular compounds from plant extracts is relevant today because of the development of resistant strains. The aim of the study was to evaluate the antimycobacterial activity of the leave extracts of Croton gratissimus and Leonotis leonorus. The first step was to extract fine powder leaves of the two plant species using four (dichloromethane, acetone, hexane and ethanol/water) different solvent systems. Isolation of the fractions was done using column chromatography and preparative thin layer chromatography. Minimum inhibitory concentrations were determined using the broth dilution method and the values were recorded in μg/mL. All the isolated fractions from both plant species were evaluated for preliminary in-vitro antimycobacterial activity. Some of the isolated fractions showed an increased activity against the pathogen as compared to the crude extracts. All the crude extracts of the two plants had activity with MIC90 values greater than 125 μg/mL. Seven fractions obtained from Croton gratissimus showed potential activity against the pathogen with MIC90 values ranging from 30.61 to 64.88 μg/mL. Leonotis leonurus had three fractions with promising activity with MICs ranging from 1.963 to 62.51 μg/mL. The crude extracts of the two plant species showed that the two plant species have antioxidant properties. The qualitative antioxidant assay showed that DCM crude extracts had more antioxidants than all other extracts because of more clear zones against the purple background colour on the TLC plates. These was confirmed by the qualitative antioxidant assay where DCM crude extracts was able to inhibit the highest percentage of DPPH at different concentrations than all other solvent extracts. The DCM crude extracts of L. leonurus and Croton gratissimus inhibited 87 and 93 % of DPPH respectively at 250 μg/mL. The structures of the compounds within the isolated fractions were elucidated using NMR and confirmed by MS and FTIR spectroscopies. The NMR data showed that the isolated fractions were not pure compounds but mixtures of closely related compounds. The compounds whose structures were elucidated included two labdane diterpenoids (Croton A and Croton B) and a Cembranolide ((5E,10E,13R)-4-isopropyl-7,11-dimethyl-15-oxo-14-oxa-bicyclo [11.2.1] hexadeca-5,10-dien-7-yl acetate) from Croton gratissimus and a phenol (4-(3,3,4,4-tetramethylheptyl) benzene-1,2-diol)) from Leonotis leonurus. / National Research Foundation (NRF) and Sasol Foundation

No description available.

No / The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of airborne microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of airborne microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations.

No description available.

No description available.

The problem of this study was to review within Dallas and Tarrant Counties the relationship between an "influenza-like" illness within six months prior to contracting Mycobacterium kansasii disease. An interview instrument was developed and used during personal interviews to collect data. Additional data of case rates and reported cases was compiled from local and national governmental public health agencies. Analysis of the data indicated no significant difference between an individual contracting an "influenzalike" illness within six months prior to the acquiring of Mycobacterium kansasii disease. Therefore, there is no relationship between having had influenza-like symptoms within six months of contracting Mycobacteria kansasii.

Tuberculosis remains one of the oldest diseases known to mankind but still persists as a very major risk. Discovery of several antimycobacterials was marked by a steady decline in the active cases of pulmonary tuberculosis. However, in the recent past there has been a surge in its clinical incidence. The reasons for this failure are the emergence of multi drug resistance and the ability of the organism to survive under extreme condition or for a very long period of time known as ‘persistence’. The latter one established itself as a major hindrance in the effective control of tuberculosis. The latent bacilli are confined for a very long period after the infection in caseous cavities, called granulomma, inside the host and gets reactivated any time when the host becomes immuno-compromised. Latency has been successfully simulated in vitro by various models which mimic the in vivo condition by depleting O2 (Wayne, 1977), nutrients (Nyka, 1974) or the carbon source (Ojha et al., 2000). Stationary phase is exemplary of a stage in bacterial growth where the organism is exposed to various stresses like nutrient starvation, accumulation of toxic metabolites, low temperature, high osmolarity and acidity to name a few. Some evidences suggest that cells survive in nutrient deprived stationary phase. The present investigation was pursued with an objective to further our understanding on the mechanism of adaptation that the persistent mycobacterium may undertake to survive during the stationary phase of growth. The fast growing M.smegmatis, a nonpathogenic member in the non-tuberculous genera, however, with a genetic and metabolic similarity to M.tuberculosis has been used as a model for this study. Chapter 1 introduces the challenges in tuberculosis therapy and discusses the reason for drug tolerance and persistence of M.tuberculosis and M.avium complexes that were uncovered recently. It focuses on the intricate lipid rich cell wall which forms the first barrier for drug delivery with an emphasis on the cell surface antigenic glycolipids, the glycopeptidolipids. A detail account of their structure, biosynthetic pathway, intracellular function and their implications on biofilm formation has been provided. The evolution of the genetic approaches currently used in mycobacterial research is highlighted. The transcription apparatus and the regulation of gene expression in mycobacteria at different environmental condition and stages of growth are also discussed. The need for a detail investigation of the stationary phase RNAP in mycobacteria is stressed. Chapter 2 observes the changes in the cell surface of M.smegmatis at different ambience of growth. It focuses on the composition of glycopeptidolipid, one of the non-covalently attached free lipids and the mycolic-acids which are covalently attached to the inner layer of the cell wall. Composition of the mycobacterial cell wall with respect to the glycopeptidolipids and mycolic acids during biofilm mode of growth is also addressed. This chapter examines the conditional synthesis of a novel class of polar glycopeptidolipid in carbon starved cultures of M.smegmatis and determines their molecular structure. Chapter 3 revisits the biosynthetic pathway of the glycopeptidolipids and justifies a need for a fresh perspective. It identifies a glycosyltransferase responsible for the transfer of an extra rhamnose to the existing rhamnose linked to the terminal alaninol in the new polar glycopeptidolipid. This chapter also identifies a conserved Polyketide synthase in the glycopeptidolipid biosynthetic cluster. Characterization of the domains present in its two distinct modules with a correlation to the structure of the fatty acylchain together with the formation of a hydroxy fatty acyl chain is delineated. Chapter 4 deals with the construction of a suicide vector which when recombines to the mc2155 genome, incorporates a hexa-histidine tag at the C’ of the β΄ subunit of the RNAP. It details the strategy for the construction of the strain and established the genetic exchange event both genotypically and phenotypically. A single step procedure for purification of the holo-RNAP is also described in this chapter. In chapter 5 the role of the mycobacterial principal likes sigma factor, SigB, at the stationary phase of growth is highlighted. An approach of expression proteomics involving differential display of the total protein was undertaken to investigate the genes that are under the SigB regular during the stationary phase of growth. This chapter also examines the stationary phase induced changes in the RNAP. Various proteins that interact with the assembly are identified and their role in conferring rifampicin resistance to the RNAP is described. Appendix 1 details the preparation of the partially methylated deoxy monosaccharide using the esoteric reactions of organic synthesis. They were used extensively for glycosyl linkage analysis of the glycopeptidolipids by mass spectrometry, where they acted as standards.