Characterization and gene expression of transmissible Mycobacterium Tuberculosis strains in South Africa

Muller, Odelia (2008-03)

Thesis (MSc) -- Stellenbosch University, 2008

Thesis

ENGLISH ABSTRACT: The Mycobacterium tuberculosis Beijing strain family is a dominant strain family in most countries world wide, including South Africa. It has been suggested that this strain family has unique properties. These include the ability to evade the protective effect of Bacillus Calmette-Guérin vaccination, spread more readily and the more frequent acquisition of drug resistance. These properties might be the reasons for the Beijing strain’s successful transmission. Comparative genomics have suggested that strains from the Beijing family can be broadly grouped into typical and atypical strains according to the presence or absence of an IS6110 insertion in the NTF region in the genome of Mycobacterium tuberculosis. Phylogenetic analysis showed that these two groups originated from a common progenitor. However, the atypical Beijing strain has only rarely been identified. The atypical Beijing strains are also not frequently associated with drug resistance, is attenuated and therefore do not spread readily. In contrast, by applying molecular epidemiological techniques, this study showed that an atypical Beijing strain acquired drug resistance and was spreading amongst tuberculosis re-treatment patients in the Eastern Cape province of South Africa. Further molecular analysis showed that this strain had a high fitness cost mutation in the rpoB gene, conferring rifampicin resistance. This correlates with in vitro generated rpoB mutants. The human immune deficiency virus/tuberculosis co-infection was found to be a significant co-factor, which allowed the atypical Beijing strain to be transmitted. Therefore, the attenuated atypical Beijing strain can overcome its fitness cost in high human immune deficiency virus burdened communities and may cause ongoing transmission. This raises concern for the spread of all drug-resistant strains in vulnerable populations. By analysing a longitudinal reference database at the University of Stellenbosch, it has been observed that the strain dynamics within a strain family differs. There are large and small clusters in the Beijing strain family which is suggestive of more and less transmissible strains. Comparative proteomic analysis by 2-D gel electrophoresis identified 64 protein spots which were different between a large and small cluster in the Beijing strain family. Similarly, 59 protein spots were found different between the attenuated atypical Beijing strain and the typical large Beijing cluster. By comparing the atypical Beijing strain to the small Beijing cluster it was found that 132 protein spots were different between the two strains. These results strongly suggest that differential expression of certain genes is associated with differential transmission of different Beijing sub-lineages. The same may be true for other Mycobacterium tuberculosis strain families. It is likely that the bacterial genomic background play a more dominant role in the differential transmission of certain Mycobacterium tuberculosis strains, than host or programmatic related factors. A more comprehensive study, which involves the bacterium, host, and the tuberculosis control program, is needed to prove this assumption.

AFRIKAANSE OPSOMMING: Die Mycobacterium tuberculosis Beijing familie is ‘n prominent in meeste lande wêreld wyd, insluitende Suid-Afrika. Bevindings toon dat hierdie familie unieke eienskappe besit. Dit sluit in die vermoëe om die uitwerking van die Bacillus Calmette-Guérin vaksien te ontduik, maklik te versprei, en die vermoeë om meer gereeld middel weerstandigheid te verkry, en daarom so suksesvol is. Vergelykbare genomika het getoon dat stamme wat aan die Beijing familie behoort, in twee sub-groepe verdeel kan word naamlik, tipies en atipies as gevolg van die aanwesigheid of afwesigheid van ‘n spesifieke IS6110 invoeging in die NTF area van die Mycobacterium tuberculosis genoom. Filogenetiese analises het verder getoon dat die twee groepe ‘n gemeenskaplike oorsprong het maar die atipiese Beijing sub-groep is meer skaars en word nie dikwels met middel weerstandigheid geassosieer nie, en versprei daarom nie so maklik nie. In teenstelling, deur die toepassing van molekulere epidemiologiese tegnieke, het hierdie studie getoon dat daar ‘n atipiese Beijing stam in die Oos-Kaap provinsie van Suid-Afrika gevind is, wat wel middel weerstandig is en versprei het tussen tuberkulose pasiente wat weer op behandeling is. Verdere molekulere analises het getoon dat die atipiese Beijing stam ‘n hoë fiksheid verlies mutasie in die rpoB geen het wat rifampisien weerstandigheid veroorsaak. Hierdie bevinding korreleer met in vitro gegenereerde rpoB mutante. Die studie het gevind dat menslike immuniteitsgebrek-virus/tuberkulose ko-infeksie ‘n belangrike faktor was in die verspreiding van hierdie stam. Dus, die minder virulente atipiese Beijing stam kan fiksheid verlies oorkom in gemeenskappe wat belas is met menslike imuniteits virus, en kan dus voortdurende transmisie veroorsaak. Hierdie bevinding wek kommer oor die verspreiding van alle middel weerstandige Mycobacterium tuberculosis stamme in kwesbare gemeenskappe. Mycobacterium tuberculosis Die ontleding van ‘n aaneenlopende databasis van die Universiteit van Stellenbosch het getoon dat die dinamika van stamme binne ‘n stam familie verskil. Daar kom groot en klein groepe in die Beijing stam familie voor wat bes moontlik op stamme wat met onderskeidelik ‘n hoe en lae oordraaglikheid dui. Vergelykende proteomiese analise deur middle van 2-D elektroforese het 64 protein verskille opgelewer tussen ‘n groot en klein stam van die Beijing stam familie. Netso is 59 protein verskille gevind toe die groot tipiese Beijing stam en die geattenueerde atipiese Beijing stam vergelyk word. “n Vergelyking tussen die klein tipiese Beijing stam en die atipiese Beijing stam het 132 protein verskille getoon. Hierdie resultate laat ‘n sterk vermoede dat differensiele uitdrukking van sekere gene geassosieer kan word met differensiele oordraag van verskillende Beijing stamme. Dieselfde mag ook geld vir ander Mycobacterium tuberculosis stam families. Dit is moontlik dat die genomiese agtergrond van die bakterium ‘n meer dominante rol by die differensiele oordraag van sekere Mycobacterium tuberculosis stamme het as ander faktore rakende die draer van die tuberkulose infeksie, of die tuberkulose-beheerprogram. Om hierdie aanname te staaf sal ‘n meer omvattende studie wat die Mycobacterium tuberculosis bakterium, die draer, en die Mycobacterium tuberculosis tuberkulose beheerprogram betrek, nodig wees.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/72024
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