Host Laboratory : Javier Pizarro-Cerda (https://research.pasteur.fr/fr/team/yersinia/ ; Institut Pasteur, Paris)
Thierry Wirth, Muséum National d’Histoire Naturelle – EPHE : Evolutionary history and adaptive landscape of the M. tuberculosis Beijing lineage
M. tuberculosis lineage 2 is one of the most widely dispersed lineages in the world, and is particularly associated with the spread of multi-resistant strains in Eurasia. However, the reasons for the success of Lineage 2 are only partially understood. My presentation will develop and underline the importance of an integrative approach to answer this question. Firstly, using Bayesian phylogenomics and demogenetics analyses, based on hundreds or thousands of complete genomes, I will illustrate the strength, spread and timing of major L2 epidemics, which highlight and confirm the dominance of this lineage both in terms of antibiotic resistance and epidemiological success. In addition, we will also see how major socio-economic events reinforce ongoing epidemics. In the second part, which focuses on the underlying mechanisms, I will summarize how predictive simulations, epidemicity indices, genome-wide association studies and, finally, laboratory fluctuation assays have enabled us to make progress on this subject.
Alexandra Moura, institut Pasteur, Paris : The genomic landscape of Listeria monocytogenes: insights into pathogenesis, epidemiology, and evolutionary dynamics
Listeria monocytogenes is a foodborne bacterial pathogen that can cause listeriosis, a rare but severe infection. Despite effective antibiotic treatment, listeriosis exhibits the highest hospitalization and fatality rates among foodborne illnesses, rendering it a significant public health concern. The incidence of listeriosis is increasing in industrialized countries, and can occur in large outbreaks, as recently reported in Spain and South Africa.
Population diversity studies have revealed that Listeria monocytogenes is a genetically heterogeneous species, divided into four phylogenetic lineages and hundreds of clonal complexes and sublineages. Yet, most clinical infections are attributed to a few clonal complexes distributed worldwide, with heterogeneous virulence and antimicrobial resistance properties.
Over two decades have passed since the sequencing of the first Listeria genome and significant sequencing data has been accumulated since, allowing to capture a more precise picture of its ecology, diversity, and population dynamics.
In this talk, we will discuss how genomics has significantly advanced our understanding of Listeria pathogenesis and evolution, shedding light on its zoonotic reservoirs and providing invaluable insights into the emergence and global dissemination of the main clinical clones.
Cyril Savin, Institut Pasteur, Paris : Circulation, evolution and genetic diversity of Yersinia pseudotuberculosis
Yersinia pseudotuberculosis (Ypstb) is a pathogen of the gastrointestinal tract, closely related to Y. pestis, the plague agent. The population structure of Ypstb has been determined using a cgMLST developed in the Yersinia National Reference Laboratory. The population is composed by 155 different genotypes. The epidemiology study of these genotypes revealed that some are restricted to a specific geographical area whereas others are spread worldwide. Two genotypes (1 and 8) are associated with a peculiar form of infection (Far east scarlet-like fever) and two others (5 and 6) are associated with an invasive form of infection, suggesting higher virulence. Phylogenetic analysis showed that Y. pestis represents a genotype of Ypstb, and that genotype 5 is its closest relative. Spatial and temporal diffusion study of Ypstb revealed that this species emerged in Asia before reaching Europe, where it started to spread worldwide. The evolution study of the species revealed that different processes (gene acquisition/loss, SNP, insertion sequences) led to the emergence of diverse genotypes with differential virulence potential.
