TUBERCULOSIS: The variation in virulence between distinct M. tuberculosis strains

Author: Hiwa MalenGustavo De SouzaSharad PathakTina SoftelandHarald Wiker
Credits/Source: BMC Microbiology 2011, 11:18


The potential causes for variation in virulence between distinct M. tuberculosis strains are still not fully known. However, differences in protein expression are probably an important factor. In this study we used a label-free quantitative proteomic approach to estimate differences in protein abundance between two closely related M. tuberculosis strains; the virulent H37Rv strain and its attenuated counterpart H37Ra.

Results: We were able to identify more than 1700 proteins from both strains.
As expected, the majority of the identified proteins had similar relative abundance in the two strains. However, 29 membrane-associated proteins were observed with a 5 or more fold difference in their relative abundance in one strain compared to the other.
Of note, 19 membrane- and lipo-proteins had higher abundance in H37Rv, while another 10 proteins had a higher abundance in H37Ra. Interestingly, the possible protein-export membrane protein SecF (Rv2586c), and three ABC-transporter proteins (Rv0933, Rv1273c and Rv1819c) were among the more abundant proteins in M. tuberculosis H37Rv.

Conclusion: Our data suggests that the bacterial secretion system and the transmembrane transport system may be important determinants of the ability of distinct M.tuberculosis strains to cause disease.
http://7thspace.com/headlines/370542/comparison_of_membrane_proteins_of_mycobacterium_tuberculosis_h37rv_and_h37ra_strains.html

TUBERCULOSIS: Changes in Mycobacterium tuberculosis Genotype Families Over 20 Years in a Population-Based Study in Northern Malawi

August 19, 2010
Background
Despite increasing interest in possible differences in virulence and transmissibility between different genotypes of M. tuberculosis, very little is known about how genotypes within a population change over decades, or about relationships to HIV infection.
Methods and Principal Findings
In a population-based study in rural Malawi we have examined smears and cultures from tuberculosis patients over a 20-year period using spoligotyping. Isolates were grouped into spoligotype families and lineages following previously published criteria. Time trends, HIV status, drug resistance and outcome were examined by spoligotype family and lineage. In addition, transmissibility was examined among pairs of cases with known epidemiological contact by assessing the proportion of transmissions confirmed for each lineage, on the basis of IS6110 RFLP similarity of the M tuberculosis strains. 760 spoligotypes were obtained from smears from 518 patients from 1986–2002, and 377 spoligotypes from cultures from 347 patients from 2005–2008. There was good consistency in patients with multiple specimens. Among 781 patients with first episode tuberculosis, the majority (76%) had Lineage 4 (“European/American”) strains; 9% had Lineage 3 (“East-African/Indian”); 8% Lineage 1 (“Indo-Oceanic”); and 2% Lineage 2 (“East-Asian”); others unclassifiable. Over time the proportion of Lineage 4 decreased from >90% to 60%, with an increase in the other 3 lineages (p>HIV infection, even after adjusting for age, sex and year. There were no associations with drug resistance or outcome, and no differences by lineage in the proportion of pairs in which transmission was confirmed.
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Conclusions
This is the first study to describe long term trends in the four M. tuberculosis lineages in a population. Lineage 4 has probably been longstanding in this population, with relatively recent introductions and spread of Lineages1–3, perhaps influenced by the HIV epidemic.
http://elitestv.com/pub/2010/08/changes-in-mycobacterium-tuberculosis-genotype-families-over-20-years-in-a-population-based-study-in-northern-malawi