Search

International audience; No abstract available

International audience; Infectious diseases are among the strongest selective pressures driving human evolution1,2. This includes the single greatest mortality event in recorded history, the first outbreak of the second pandemic of plague, commonly called the Black Death, which was caused by the bacterium Yersinia pestis3. This pandemic devastated Afro-Eurasia, killing up to 30-50% of the population4. To identify loci that may have been under selection during the Black Death, we characterized genetic variation around immune-related genes from 206 ancient DNA extracts, stemming from two different European populations before, during and after the Black Death. Immune loci are strongly enriched for highly differentiated sites relative to a set of non-immune loci, suggesting positive selection. We identify 245 variants that are highly differentiated within the London dataset, four of which were replicated in an independent cohort from Denmark, and represent the strongest candidates for positive selection. The selected allele for one of these variants, rs2549794, is associated with the production of a full-length (versus truncated) ERAP2 transcript, variation in cytokine response to Y. pestis and increased ability to control intracellular Y. pestis in macrophages. Finally, we show that protective variants overlap with alleles that are today associated with increased susceptibility to autoimmune diseases, providing empirical evidence for the role played by past pandemics in shaping present-day susceptibility to disease.

Strains of the genus Tsukamurella were isolated from Polybia sp. social wasps from Costa Rica. Draft genome sequences from both isolates were obtained of ~4.5 Mb in length and with 68% GC content.

International audience; This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Bartonet al.1raise several statistical concerns regarding our original analyses2that highlight the challenge of inferring natural selection using ancient genomic data. We show here that these concerns have limited impact on our original conclusions. Specifically, we recover the same signature of enrichment for high FSTvalues at the immune loci relative to putatively neutral sites after switching the allele frequency estimation method to a maximum likelihood approach, filtering to only consider known human variants, and down-sampling our data to the same mean coverage across sites. Furthermore, using permutations, we show that the rs2549794 variant nearERAP2continues to emerge as the strongest candidate for selection (p = 1.2×10−5), falling below the Bonferroni-corrected significance threshold recommended by Bartonet al. Importantly, the evidence for selection onERAP2is further supported by functional data demonstrating the impact of theERAP2genotype on the immune response toY. pestisand by epidemiological data from an independent group showing that the putatively selected allele during the Black Death protects against severe respiratory infection in contemporary populations.

International audience; Plague is an often fulminant and fatal disease caused by the bacterial pathogen Yersinia pestis. Three major historical plague pandemics have heavily influenced human societies, and recent evidence demonstrates that plague has also influenced human biology. Plague is still endemic in several continents and remains a potential public health risk. In this article, we examine the current situation of plague around the world and the different players that participate in plague ecosystems. We discuss in particular the recent research that allows us to understand plague in pre-historical times, as well as how past pandemics have modulated the evolution of human immune genes. We also highlight future challenges that await us in the study of this deadly but fascinating disease.

International audience; The genus Yersinia includes a large variety of nonpathogenic and life-threatening pathogenic bacteria, which cause a broad spectrum of diseases in humans and animals, such as plague, enteritis, Far East scarlet-like fever (FESLF), and enteric redmouth disease. Like most clinically relevant microorganisms, Yersinia spp. are currently subjected to intense multi-omics investigations whose numbers have increased extensively in recent years, generating massive amounts of data useful for diagnostic and therapeutic developments. The lack of a simple and centralized way to exploit these data led us to design Yersiniomics, a web-based platform allowing straightforward analysis of Yersinia omics data. Yersiniomics contains a curated multi-omics database at its core, gathering 200 genomic, 317 transcriptomic, and 62 proteomic data sets for Yersinia species. It integrates genomic, transcriptomic, and proteomic browsers, a genome viewer, and a heatmap viewer to navigate within genomes and experimental conditions. For streamlined access to structural and functional properties, it directly links each gene to GenBank, the Kyoto Encyclopedia of Genes and Genomes (KEGG), UniProt, InterPro, IntAct, and the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and each experiment to Gene Expression Omnibus (GEO), the European Nucleotide Archive (ENA), or the Proteomics Identifications Database (PRIDE). Yersiniomics provides a powerful tool for microbiologists to assist with investigations ranging from specific gene studies to systems biology studies. IMPORTANCE The expanding genus Yersinia is composed of multiple nonpathogenic species and a few pathogenic species, including the deadly etiologic agent of plague, Yersinia pestis. In 2 decades, the number of genomic, transcriptomic, and proteomic studies on Yersinia grew massively, delivering a wealth of data. We developed Yersiniomics, an interactive web-based platform, to centralize and analyze omics data sets on Yersinia species. The platform allows user-friendly navigation between genomic data, expression data, and experimental conditions. Yersiniomics will be a valuable tool to microbiologists.

International audience; Yersinia pseudotuberculosis is an enteric pathogen causing mild enteritis that can lead to mesenteric adenitis in children and septicemia in elderly patients. Most cases are sporadic, but outbreaks have already been described in different countries. We report for the first time a Y. pseudotuberculosis clonal outbreak in France, that occurred in 2020. An epidemiological investigation based on food queries pointed toward the consumption of tomatoes as the suspected source of infection. The Yersinia National Reference Laboratory (YNRL) developed a new cgMLST scheme with 1,921 genes specific to Y. pseudotuberculosis that identified the clustering of isolates associated with the outbreak and allowed to perform molecular typing in real time. In addition, this method allowed to retrospectively identify isolates belonging to this cluster from earlier in 2020. This method, which does not require specific bioinformatic skills, is now used systematically at the YNRL and proves to display an excellent discriminatory power and is available to the scientific community.

Thirty-three Yersinia strains previously characterized by the French Yersinia National Reference Laboratory (YNRL) and isolated from humans and animals were suspected to belong to six novel species by a recently described core genome multilocus sequence typing scheme. These strains and five additional strains from the YNRL were characterized using a polyphasic taxonomic approach including a phylogenetic analysis based on 500 core genes, determination of average nucleotide identity (ANI), determination of DNA G+C content and identification of phenotypic features. Phylogenetic analysis confirmed that the 38 studied strains formed six well-demarcated clades. ANI values between these clades and their closest relatives were 97.5 %. Distinctive biochemical characteristics were identified in five out of the six novel species. All of these data demonstrated that the 38 strains belong to six novel species of the genus Yersinia : Yersinia artesiana sp. nov., type strain IP42281T (=CIP 111845T=DSM 110725T); Yersinia proxima sp. nov., type strain IP37424T (=CIP 111847T=DSM 110727T); Yersinia alsatica sp. nov., type strain IP38850T (=CIP 111848T=DSM 110726T); Yersinia vastinensis sp. nov., type strain IP38594T (=CIP 111844T=DSM 110738T); Yersinia thracica sp. nov., type strain IP34646T (=CIP 111842T=DSM 110736T); and Yersinia occitanica sp. nov., type strain IP35638T (=CIP 111843T=DSM 110739T).

Yersinia pseudotuberculosisis an enteric pathogen causing mild enteritis that can lead to mesenteric adenitis and septicemia in elderly patients. Most cases are sporadic, but outbreaks have already been described in different countries. We report for the first time aY. pseudotuberculosisclonal outbreak in France, that occurred in 2020. An epidemiological investigation pointed towards the consumption of tomatoes as the likely source of contamination. TheYersiniaNational Reference Laboratory (YNRL) developed a new cgMLST scheme with 1,921 genes specific toY. pseudotuberculosisthat identified the clustering of isolates associated to the outbreak and allowed to perform molecular typing in real time. In addition, this method allowed to retrospectively identify isolates belonging to this cluster from earlier in 2020. This method, which does not require specific bioinformatic skills, is now used systematically at the YNRL and proves to display an excellent discriminatory power and is available to the scientific community.

Significance Listeria monocytogenes (Lm) is a bacterial pathogen that causes listeriosis, a foodborne disease characterized by gastroenteritis, meningitis, bacteremia, and abortions in pregnant women. The most severe human listeriosis outbreaks are associated with a subset of Lm hypervirulent clones that encode the bacteriocin Listeriolysin S (LLS), which modifies the gut microbiota and allows efficient Lm gut colonization and invasion of deeper organs. Our present work identifies the killing mechanism displayed by LLS to outcompete gut commensal bacteria, demonstrating that it induces membrane permeabilization and membrane depolarization of target bacteria. Moreover, we show that LLS is a thiazole/oxazole–modified microcin that displays a contact-dependent inhibition mechanism., Listeriolysin S (LLS) is a thiazole/oxazole–modified microcin (TOMM) produced by hypervirulent clones of Listeria monocytogenes. LLS targets specific gram-positive bacteria and modulates the host intestinal microbiota composition. To characterize the mechanism of LLS transfer to target bacteria and its bactericidal function, we first investigated its subcellular distribution in LLS-producer bacteria. Using subcellular fractionation assays, transmission electron microscopy, and single-molecule superresolution microscopy, we identified that LLS remains associated with the bacterial cell membrane and cytoplasm and is not secreted to the bacterial extracellular space. Only living LLS-producer bacteria (and not purified LLS-positive bacterial membranes) display bactericidal activity. Applying transwell coculture systems and microfluidic-coupled microscopy, we determined that LLS requires direct contact between LLS-producer and -target bacteria in order to display bactericidal activity, and thus behaves as a contact-dependent bacteriocin. Contact-dependent exposure to LLS leads to permeabilization/depolarization of the target bacterial cell membrane and adenosine triphosphate (ATP) release. Additionally, we show that lipoteichoic acids (LTAs) can interact with LLS and that LTA decorations influence bacterial susceptibility to LLS. Overall, our results suggest that LLS is a TOMM that displays a contact-dependent inhibition mechanism.

International audience; Plague is a vector-borne disease caused by Yersinia pestis. Transmitted by fleas from rodent reservoirs, Y. pestis emerged less than 6000 years ago from an enteric bacterial ancestor through events of gene gain and genome reduction. It is a highly remarkable model for the understanding of pathogenic bacteria evolution, and a major concern for public health as highlighted by recent human outbreaks. A complex set of virulence determinants, including the Yersinia outer membrane proteins (Yops), the broad range pro-tease Pla, pathogen-associated molecular patterns (PAMPs) and iron capture systems play critical roles in the molecular strategies that Y. pestis employs to subvert the human immune system, allowing unrestricted bacterial replication in lymph nodes (bubonic plague) and in lungs (pneumonic plague). Some of these immunogenic proteins as well as the capsular antigen F1 are exploited for diagnostic purposes, which are critical in the context of the rapid onset of death in the absence of antibiotic treatment (less than a week for bubonic plague and less than 48 h for pneumonic plague). In here, we review recent research advances on Y. pestis evolution, virulence factors function, bacterial strategies to subvert mammalian innate immune responses, vaccination and problems associated to pneumonic plague diagnosis.

International audience; Immunization with the live-attenuated Yersinia pseudotuberculosis VTnF1 strain producing a Yersinia pestis F1 pseudocapsule efficiently protects mice against bubonic and pneumonic plague. In clinical trials, demonstration of a plague vaccine's efficacy in humans will not be feasible, and correlates of protection will be needed to bridge the immune response of protected animals to that of vaccinated humans. Using serum transfer and vaccination of antibody-deficient µMT mice, we established that both humoral and cellular responses elicited by VTnF1 independently conferred protection against bubonic plague. Thus, correlates were searched for in both responses, using blood only. Mice were vaccinated with increasing doses of VTnF1 to provide a range of immune responses and survival outcomes. The cellular response was evaluated using an in vitro IFNγ release assay, and IFNγ levels were significantly associated with protection, although some survivors were negative for IFNγ, so that IFNγ release is not a fully satisfactory correlate. Abundant serum IgG against the F1 capsule, Yop injectable toxins, and also non-F1 Y.pestis antigens were found, but none against the LcrV antigen. All readouts correlated to survival and to each other, confirming that vaccination triggered multiple protective mechanisms developing in parallel. Anti-F1 IgG was the most stringent correlate of protection, in both inbred BALB/c mice and outbred OF1 mice. This indicates that antibodies (Ab) to F1 play a dominant role for protection even in the presence of Ab to many other targets. Easy to measure, the anti-F1 IgG titer will be useful to evaluate the immune response in other animal species and in clinical trials.

Este artículo se encuentra disponible en la siguiente URL: https://academic.oup.com/jid/advance-article/doi/10.1093/infdis/jiaa367/5862450 En esta investigación también participan: Nathalie Aulner, Anne Danckaert, Alain Charbit, Jost Enninga, Pascale Cossart y Javier Pizarro Cerdá. The bacterial pathogen Listeria monocytogenes invades host cells, ruptures the internalization vacuole, and reaches the cytosol for replication. A high-content small interfering RNA (siRNA) microscopy screen allowed us to identify epithelial cell factors involved in L. monocytogenes vacuolar rupture, including the serine/threonine kinase Taok2. Kinase activity inhibition using a specific drug validated a role for Taok2 in favoring L. monocytogenes cytoplasmic access. Furthermore, we showed that Taok2 recruitment to L. monocytogenes vacuoles requires the presence of pore-forming toxin listeriolysin O. Overall, our study identified the first set of host factors modulating L. monocytogenes vacuolar rupture and cytoplasmic access in epithelial cells.

International audience; Yersinia pseudotuberculosis, Y. enterocolitica and Y. pestis are pathogenic bacteria capable of causing disease in humans by growing extracellularly in lymph nodes and during systemic infections. While the capacity of these bacteria to invade, replicate, and survive within host cells has been known for long, it is only in recent years that their intracellular stages have been explored in more detail. Current evidence suggests that pathogenic Yersinia are capable of activating autophagy in both phagocytic and epithelial cells, subverting autophagosome formation to create a niche supporting bacterial intracellular replication. In this review, we discuss recent results opening novel perspectives to the understanding of intimate host-pathogens interactions taking place during enteric yersiniosis and plague.

Oral administration is a preferred model for studying infection by bacterial enteropathogens such as Yersinia spp. In the mouse model, the most frequent method for oral infection consists of oral gavage with a feeding needle directly introduced in the animal stomach via the esophagus. In this study, we compared needle gavage to bread feeding as an alternative mode of bacterial administration. Using bioluminescence-expressing strains of Yersinia pseudotuberculosis and Yersinia enterocolitica, we detected very early upon needle gavage a bioluminescent signal in the neck area together with a signal in the abdominal region, highlighting the presence of two independent sites of bacterial colonization and multiplication., Oral administration is a preferred model for studying infection by bacterial enteropathogens such as Yersinia spp. In the mouse model, the most frequent method for oral infection consists of oral gavage with a feeding needle directly introduced in the animal stomach via the esophagus. In this study, we compared needle gavage to bread feeding as an alternative mode of bacterial administration. Using bioluminescence-expressing strains of Yersinia pseudotuberculosis and Yersinia enterocolitica, we detected very early upon needle gavage a bioluminescent signal in the neck area together with a signal in the abdominal region, highlighting the presence of two independent sites of bacterial colonization and multiplication. Bacteria were often detected in the esophagus and trachea, as well as in the lymph nodes draining the salivary glands, suggesting that lesions made during needle introduction into the animal oral cavity lead to rapid bacterial draining to proximal lymph nodes. We then tested an alternative mode of bacterial administration using pieces of bread containing bacteria. Upon bread feeding infection, mice exhibited a stronger bioluminescent signal in the abdominal region than with needle gavage, and no signal was detected in the neck area. Moreover, Y. pseudotuberculosis incorporated in the bread is less susceptible to the acidic environment of the stomach and is therefore more efficient in causing intestinal infections. Based on our observations, bread feeding constitutes a natural and more efficient administration method which does not require specialized skills, is less traumatic for the animal, and results in diseases that more closely mimic foodborne intestinal infection.

International audience

The behaviour of 23Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes ofThis study demonstrates the presence of virulent

A single oral inoculation to mice of the live attenuated Yersinia pseudotuberculosis VTnF1 strain producing an F1 pseudocapsule protects against bubonic and pneumonic plague. However oral vaccination can fail in humans exposed to frequent intestinal infections. We evaluated in mice the efficacy of subcutaneous vaccine injection as an alternative way to induce protective immunity, while reducing the dose and avoiding strain release in nature. A single subcutaneous dose of up to 108 CFU induced dose-dependent antibody production. At the dose of 107 CFU, i.e. 10 times less than via the oral route, it caused a modest skin reaction and protected 100% against bubonic and 80% against pneumonic plague, caused by high doses of Yersinia pestis. Bacteria migrating to lymph nodes and spleen, but not feces, were rapidly eliminated. Thus, subcutaneous injection of VTnF1 would represent a good alternative when dissemination in nature and human intestinal responsiveness are limitations.

Plague is a communicable rodent-borne disease caused by Yersinia pestis, a Gram-negative bacillus member of the Enterobacteriaceae\ud family. As a zoonosis, plague is primarily a wildlife disease that occasionally spills over to the human population, resulting in seasonal surges in human cases and localised outbreaks. The predominant clinical form among humans is bubonic plague, which,\ud if untreated, has a lethality of 60%–90% but is readily treatable with antibiotics, reducing the death rate to around 5% if administered shortly after the infection. One to two per cent of all bubonic cases develop into secondary pneumonic plague, which in turn may be transmitted from person to person through respiratory droplets, producing primary pneumonic plague in close contacts.\ud Without antibiotic treatment, pneumonic plague is nearly 100% fatal, but early antibiotic treatment substantially improves survival. Today, Y. pestis is present in at least 26 countries, with more than 30 different flea vectors and over 200 mammal host species. Although human plague cases continue to be reported from Asia and the Americas, most cases currently occur in remote, rural areas\ud of sub-Saharan Africa, mostly in Democratic Republic of Congo and Madagascar (around300–500 per year). However, large-scale\ud transmission may also occur. During the 14th century, the Black Death, caused by Y. pestis, is estimated to have killed 30%–40% of the European population. It is important to emphasise that human\ud plague is mostly a poverty-related disease. Therefore, given that population density and the absolute number of people living in extreme poverty are both increasing in sub-Saharan Africa, there is no likelihood of plague being eliminated as a public health threat in the foreseeable future. However, the WHO does not consider plague to be either a neglected tropical disease or a ‘priority pathogen’ that poses a public health risk because of its epidemic potential. In September 2017, an unprecedented urban outbreak of pneumonic plague was declared in Madagascar, striking primarily its capital Antananarivo and the major seaport of Toamasina. This episode once again brought international attention to plague, reminding\ud us of the capacity for human plague to spread in urban settings and cause substantial societal and economic disruption. This should\ud raise alarm bells that a research agenda is needed.

Oral administration is a preferred model for studying infection by bacterial enteropathogens such asYersinia. In the mouse model, the most frequent method for oral infection consists of oral gavage with a feeding needle directly introduced in the animal stomach via the esophagus. In this study, we compared needle gavage to bread feeding as an alternative mode of bacterial administration. Using a bioluminescence-expressing strain ofYersinia pseudotuberculosis, we detected very early upon needle gavage a bioluminescent signal in the neck area together with a signal in the abdominal region, highlighting the presence of two independent sites of bacterial colonization and multiplication. Bacteria were often detected in the esophagus and trachea, as well as in the lymph nodes draining the salivary glands, suggesting that lesions made during needle introduction into the animal oral cavity lead to rapid bacterial draining to proximal lymph nodes. We then tested an alternative mode of bacterial administration using small pieces of white bread containing bacteria. Upon bread feeding infection, mice exhibited a stronger bioluminescent signal in the abdominal region as compared to needle gavage, and no signal was detected in the neck area. Moreover,Y. pseudotuberculosisincorporated in the bread is less susceptible to the acidic environment of the stomach and is therefore more efficient in causing intestinal infections. Based on our observations, bread feeding constitutes a natural and more efficient administration method which does not require specialized skills, is less traumatic for the animal, and results in diseases that more closely mimic food-borne intestinal infection.

The genus Yersinia comprises species that differ widely in their pathogenic potential and public-health significance. Yersinia pestis is responsible for plague, while Yersinia enterocolitica is a prominent enteropathogen. Strains within some species, including Y. enterocolitica, also vary in their pathogenic properties. Phenotypic identification of Yersinia species is time-consuming, labour-intensive and may lead to incorrect identifications. Here, we developed a method to automatically identify and subtype all Yersinia isolates from their genomic sequence. A phylogenetic analysis of Yersinia isolates based on a core subset of 500 shared genes clearly demarcated all existing Yersinia species and uncovered novel, yet undefined Yersinia taxa. An automated taxonomic assignment procedure was developed using species-specific thresholds based on core-genome multilocus sequence typing (cgMLST). The performance of this method was assessed on 1843 isolates prospectively collected by the French National Surveillance System and analysed in parallel using phenotypic reference methods, leading to nearly complete (1814; 98.4 %) agreement at species and infra-specific (biotype and serotype) levels. For 29 isolates, incorrect phenotypic assignments resulted from atypical biochemical characteristics or lack of phenotypic resolution. To provide an identification tool, a database of cgMLST profiles and reference taxonomic information has been made publicly accessible (https://bigsdb.pasteur.fr/yersinia). Genomic sequencing-based identification and subtyping of any Yersinia is a powerful and reliable novel approach to define the pathogenic potential of isolates of this medically important genus.

International audience; The genus Yersinia comprises species that differ widely in their pathogenic potential and public-health significance. Yersinia pestis is responsible for plague, while Yersinia enterocolitica is a prominent enteropathogen. Strains within some species, including Y. enterocolitica, also vary in their pathogenic properties. Phenotypic identification of Yersinia species is time-consuming, labour-intensive and may lead to incorrect identifications. Here, we developed a method to automatically identify and subtype all Yersinia isolates from their genomic sequence. A phylogenetic analysis of Yersinia isolates based on a core subset of 500 shared genes clearly demarcated all existing Yersinia species and uncovered novel, yet undefined Yersinia taxa. An automated taxo-nomic assignment procedure was developed using species-specific thresholds based on core-genome multilocus sequence typing (cgMLST). The performance of this method was assessed on 1843 isolates prospectively collected by the French National Surveillance System and analysed in parallel using phenotypic reference methods, leading to nearly complete (1814; 98.4 %) agreement at species and infra-specific (biotype and serotype) levels. For 29 isolates, incorrect phenotypic assignments resulted from atypical biochemical characteristics or lack of phenotypic resolution. To provide an identification tool, a database of cgMLST profiles and reference taxonomic information has been made publicly accessible (https:// bigsdb. pasteur. fr/ yers-inia). Genomic sequencing-based identification and subtyping of any Yersinia is a powerful and reliable novel approach to define the pathogenic potential of isolates of this medically important genus.

Bioluminescence imaging (BLI) has become a major strategy for real-time analysis of dynamic biological processes. In particular, bioluminescent reporter microorganisms have been designed to advance our understanding of infectious diseases. Non-invasive monitoring of light-emitting pathogenic bacteria has revealed novel features of pathogenesis and enabled quantitative and qualitative analysis of antibacterial therapies. Transcriptional gene fusions using the bacterial luciferase operon luxCDABE as a reporter have been successfully used to monitor gene expression in vitro and in vivo, leading to valuable applications and major findings. In this chapter, we describe the construction of Yersinia pestis strains bearing a chromosomal copy of the luxCDABE operon under the control of promoters regulated by temperature and their application to quantify gene expression in real-time in bacteria growing in vitro and in a murine bubonic plague model.

International audience; Bioluminescence imaging (BLI) has become a major strategy for real-time analysis of dynamic biological processes. In particular, bioluminescent reporter microorganisms have been designed to advance our understanding of infectious diseases. Non-invasive monitoring of light-emitting pathogenic bacteria has revealed novel features of pathogenesis and enabled quantitative and qualitative analysis of antibacterial therapies. Transcriptional gene fusions using the bacterial luciferase operon luxCDABE as a reporter have been successfully used to monitor gene expression in vitro and in vivo, leading to valuable applications and major findings. In this chapter, we describe the construction of Yersinia pestis strains bearing a chromosomal copy of the luxCDABE operon under the control of promoters regulated by temperature and their application to quantify gene expression in real-time in bacteria growing in vitro and in a murine bubonic plague model.

Listeria monocytogenes is a food-borne bacterial pathogen that is responsible for listeriosis, a disease characterized by occasional febrile gastroenteritis in immunocompetent individuals, abortions in pregnant women, meningitis in the newborn and fatal bacteraemia in immunocompromised individuals or the elderly. The ability of L. monocytogenes to produce disease is intimately associated with its potential to traverse several human barriers (including the intestinal, placental and blood/brain barriers), to promote its internalization within diverse populations of epithelial cells and to proliferate in the intra-ic environment while escaping host immune responses. L. monocytogenes is often regarded as a paradigm for intracellular parasitism.

Yersinia enterocolitica, a member of the Enterobacteriaceae family, is a gastrointestinal pathogen. This species is transmitted via the fecal-oral route, usually through the consumption of contamin...

International audience; Bacterial pathogens display an impressive arsenal of molecular mechanisms that allow survival in diverse host niches. Subversion of plasma membrane and cytoskeletal functions are common themes associated to infection by both extracellular and intracellular pathogens. Moreover, intracellular pathogens modify the structure/stability of their membrane-bound compartments and escape degradation from phagocytic or autophagic pathways. Here, we review the manipulation of host membranes by Listeria monocytogenes, Francisella tularensis, Shigella flexneri and Yersinia spp. These four bacterial model pathogens exemplify generalized strategies as well as specific features observed during bacterial infection processes.

International audience; Background: Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis, an infectious disease of animals and humans, with pigs acting as asymptomatic reservoirs. In August 2019 a listeriosis outbreak associated with the consumption of pork meat caused 222 human cases in Spain. Determining the diversity as well as the virulence potential of strains from pig origin is important for public health concerns. Methods: The behavior of twenty-three L. monocytogenes strains recovered from pig tonsils, meat and skin was compared by studying: (1) Internalin A (InlA), Internalin B (InlB), Listeriolysin O (LLO), Actin assembly-inducing protein (ActA) and PrfA expression levels, and (2) invasion and intracellular growth in eukaryotic cells. Results: Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes of the L. monocytogenes strains. Strains obtained from meat samples and belonging to ST 1/2a did not have InlA anchored to the peptidoglycan. Some strains expressed higher levels of the studied virulence factors and invaded and replicated intracellularly more efficiently than an epidemic L. monocytogenes reference strain (F2365). Conclusion: This study demonstrates the presence of virulent L. monocytogenes strains in pigs, with valuable implications in veterinary medicine and food safety.