The seventh cholera pandemic has heavily affected Africa, although the origin and continental spread of the disease remain undefined. We used genomic data from 1070 Vibrio cholerae O1 isolates, across 45 African countries and over a 49-year period, to show that past epidemics were attributable to a single expanded lineage. This lineage was introduced at least 11 times since 1970, into two main regions, West Africa and East/Southern Africa, causing epidemics that lasted up to 28 years. The last five introductions into Africa, all from Asia, involved multidrug-resistant sublineages that replaced antibiotic-susceptible sublineages after 2000. This phylogenetic framework describes the periodicity of lineage introduction and the stable routes of cholera spread, which should inform the rational design of control measures for cholera in Africa

Members of the transforming growth factor beta1 (TGF-beta) superfamily--namely, TGF-beta and BMP2--applied to undifferentiated murine embryonic stem cells up-regulated mRNA of mesodermal (Brachyury) and cardiac specific transcription factors (Nkx2.5, MEF2C). Embryoid bodies generated from stem cells primed with these growth factors demonstrated an increased potential for cardiac differentiation with a significant increase in beating areas and enhanced myofibrillogenesis. In an environment of postmitotic cardiomyocytes, stem cells engineered to express a fluorescent protein under the control of a cardiac promoter differentiated into fluorescent ventricular myocytes beating in synchrony with host cells, a process significantly enhanced by TGF-beta or BMP2. In vitro, disruption of the TGF-beta/BMP signaling pathways by latency-associated peptide and/or noggin prevented differentiation of stem cells. In fact, only host cells that secrete a TGF-beta family member induced a cardiac phenotype in stem cells. In vivo, transplantation of stem cells into heart also resulted in cardiac differentiation provided that TGF-beta/BMP2 signaling was intact. In infarcted myocardium, grafted stem cells differentiated into functional cardiomyocytes integrated with surrounding tissue, improving contractile performance. Thus, embryonic stem cells are directed to differentiate into cardiomyocytes by signaling mediated through TGF-beta/BMP2, a cardiac paracrine pathway required for therapeutic benefit of stem cell transplantation in diseased heart.

Yemen is currently experiencing the largest cholera epidemic in recent history. The first cases were declared in September 2016, and over 1.1 million cases and 2,300 deaths have since been reported1. We investigated the phylogenetic relationships, pathogenesis, and antimicrobial resistance determinants by sequencing the genomes of Vibrio cholerae isolates from the Yemen epidemic and recent isolates from neighbouring regions. These 116 genomic sequences were placed within the phylogenetic context of a global collection of 1087 seventh pandemic V. cholerae serogroup O1 and O139 biotype El Tor isolates [2–4]. We show that the Yemeni isolates collected during the two epidemiological waves of the epidemic [1], —the first between September 28th 2016 and April 23rd 2017 (25,839 suspected cases) and the second beginning on April 24th, 2017 (more than one million suspected cases), — are seventh pandemic V. cholerae O1 El Tor (7PET) serotype Ogawa isolates from a single sublineage. Using genomic approaches, we link the Yemen epidemic to global radiations of pandemic V. cholerae and show that this sublineage originated from South Asia and that it caused outbreaks in East Africa before appearing in Yemen. We also show that the Yemeni isolates are susceptible to several antibiotics commonly used to treat cholera, and to polymyxins, resistance to which is used as a marker of the El Tor biotype.

Summary Phospholipases C play a role in the pathogenesis of several bacteria. Mycobacterium tuberculosis, the causative agent of tuberculosis, possesses four genes encoding putative phospholipases C, plcA, plcB, plcC and plcD. However, the contribution of these genes to virulence is unknown. We constructed four single mutants of M. tuberculosis each inactivated in one of the plc genes, a triple plcABC mutant and a quadruple plcABCD mutant. The mutants all exhibited a lower phospholipase C activity than the wild‐type parent strain, demonstrating that the four plc genes encode a functional phospholipase C in M. tuberculosis. Functional complementation of the ΔplcABC triple mutant with the individual plcA, plcB and plcC genes restored in each case about 20% of the total Plc activity detected in the parental strain, suggesting that the three enzymes contribute equally to the overall Plc activity of M. tuberculosis. RT‐PCR analysis of the plc genes transcripts showed that the expression of these genes is strongly upregulated during the first 24 h of macrophage infection. Moreover, the growth kinetics of the triple and quadruple mutants in a mouse model of infection revealed that both mutants are attenuated in the late phase of the infection emphasizing the importance of phospholipases C in the virulence of the tubercle bacillus.

The ability of the tubercle bacillus to arrest phagosome maturation is considered one major mechanism that allows its survival within host macrophages. To identify mycobacterial genes involved in this process, we developed a high throughput phenotypic cell-based assay enabling individual sub-cellular analysis of over 11,000 Mycobacterium tuberculosis mutants. This very stringent assay makes use of fluorescent staining for intracellular acidic compartments, and automated confocal microscopy to quantitatively determine the intracellular localization of M. tuberculosis. We characterised the ten mutants that traffic most frequently into acidified compartments early after phagocytosis, suggesting that they had lost their ability to arrest phagosomal maturation. Molecular analysis of these mutants revealed mainly disruptions in genes involved in cell envelope biogenesis (fadD28), the ESX-1 secretion system (espL/Rv3880), molybdopterin biosynthesis (moaC1 and moaD1), as well as in genes from a novel locus, Rv1503c-Rv1506c. Most interestingly, the mutants in Rv1503c and Rv1506c were perturbed in the biosynthesis of acyltrehalose-containing glycolipids. Our results suggest that such glycolipids indeed play a critical role in the early intracellular fate of the tubercle bacillus. The unbiased approach developed here can be easily adapted for functional genomics study of intracellular pathogens, together with focused discovery of new anti-microbials.