Clinical value of whole-genome sequencing of Mycobacterium tuberculosis

Population Genomics of Mycobacterium tuberculosis in Ethiopia Contradicts the Virgin Soil Hypothesis for Human Tuberculosis in Sub-Saharan Africa

Colonial medical reports claimed that tuberculosis (TB) was largely unknown in Africa prior to European contact, providing a "virgin soil" for spread of TB in highly susceptible populations previously unexposed to the disease [1, 2]. This is in direct contrast to recent phylogenetic models which support an African origin for TB [3-6]. To address this apparent contradiction, we performed a broad genomic sampling of Mycobacterium tuberculosis in Ethiopia. All members of the M. tuberculosis complex (MTBC) arose from clonal expansion of a single common ancestor [7] with a proposed origin in East Africa [3, 4, 8]. Consistent with this proposal, MTBC lineage 7 is almost exclusively found in that region [9-11]. Although a detailed medical history of Ethiopia supports the view that TB was rare until the 20(th) century [12], over the last century Ethiopia has become a high-burden TB country [13]. Our results provide further support for an African origin for TB, with some genotypes already present on the continent well before European contact. Phylogenetic analyses reveal a pattern of serial introductions of multiple genotypes into Ethiopia in association with human migration and trade. In place of a "virgin soil" fostering the spread of TB in a previously naive population, we propose that increased TB mortality in Africa was driven by the introduction of European strains of M. tuberculosis alongside expansion of selected indigenous strains having biological characteristics that carry a fitness benefit in the urbanized settings of post-colonial Africa.

Clinical implications of the global multidrug-resistant tuberculosis epidemic

Multidrug-resistant tuberculosis (MDR TB) is a significant threat to global health estimated to account for nearly half a million new cases and over 200,000 deaths in 2013. The number of MDR TB cases in the UK has risen over the last 15 years, with ever more complex clinical cases and associated challenging public health and societal implications. In this review, we provide an overview of the epidemiology of MDR TB globally and in the UK, outline the clinical management of MDR TB and summarise recent advances in diagnostics and prospects for new treatment.

Revisiting the role of phospholipases C in virulence and the lifecycle of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the agent of human tuberculosis has developed different virulence mechanisms and virulence-associated tools during its evolution to survive and multiply inside the host. Based on previous reports and by analogy with other bacteria, phospholipases C (PLC) of M. tuberculosis were thought to be among these tools. To get deeper insights into the function of PLCs, we investigated their putative involvement in the intracellular lifestyle of M. tuberculosis, with emphasis on phagosomal rupture and virulence, thereby re-visiting a research theme of longstanding interest. Through the construction and use of an M. tuberculosis H37Rv PLC-null mutant (ΔPLC) and control strains, we found that PLCs of M. tuberculosis were not required for induction of phagosomal rupture and only showed marginal, if any, impact on virulence of M. tuberculosis in the cellular and mouse infection models used in this study. In contrast, we found that PLC-encoding genes were strongly upregulated under phosphate starvation and that PLC-proficient M. tuberculosis strains survived better than ΔPLC mutants under conditions where phosphatidylcholine served as sole phosphate source, opening new perspectives for studies on the role of PLCs in the lifecycle of M. tuberculosis.