use multiple mechanisms to disseminate from the intestinal lamina propria to the mesenteric lymph nodes.

Unlabelled: are facultative intracellular bacterial pathogens that cause foodborne disease in humans. The bacteria can use the surface protein InlA to invade intestinal epithelial cells or transcytose across M cells in the gut, but it is not well understood how the bacteria traffic from the underlying lamina propria to the draining mesenteric lymph nodes (MLN). Previous studies indicated that associated with both monocytes and dendritic cells in the intestinal lamina propria.

Lymph node stromal cells vary in susceptibility to infection but can support the intracellular growth of Listeria monocytogenes.

Lymph node stromal cells (LNSCs) are an often overlooked component of the immune system but play a crucial role in maintaining tissue homeostasis and orchestrating immune responses. Our understanding of the functions these cells serve in the context of bacterial infections remains limited. We previously showed that Listeria monocytogenes, a facultative intracellular foodborne bacterial pathogen, must replicate within an as-yet-unidentified cell type in the mesenteric lymph node (MLN) to spread systemically.

Apolipoprotein E genotype affects innate susceptibility to infection in aged male mice.

Apolipoprotein E (ApoE) is a lipid transport protein that is hypothesized to suppress proinflammatory cytokine production, particularly after stimulation with Toll-like receptor (TLR) ligands such as lipopolysaccharide (LPS). Studies using transgenic ApoE human replacement mice (APOE) expressing one of three different allelic variants suggest that there is a hierarchy in terms of responsiveness to proinflammatory stimuli such as APOE4/E4 > APOE3/E3 > APOE2/E2. In this study, we test the hypothesis that genotype can also predict susceptibility to infection with the facultative intracellular gram-positive bacterium .

Egress of Listeria monocytogenes from Mesenteric Lymph Nodes Depends on Intracellular Replication and Cell-to-Cell Spread.

The mesenteric lymph nodes (MLN) function as a barrier to systemic spread for both commensal and pathogenic bacteria in the gut. Listeria monocytogenes, a facultative intracellular foodborne pathogen, readily overcomes this barrier and spreads into the bloodstream, causing life-threatening systemic infections. We show here that intracellular replication protected L.

Genome Sequences of Neurotropic Lineage III Listeria monocytogenes Isolates UKVDL9 and 2010L-2198.

We report the whole-genome sequence of UKVDL9 and an edited draft genome sequence of 2010L-2198. Both are neurotropic lineage III strains; UKVDL9 was isolated from a sheep brain, and 2010L-2198 was isolated from a human subject with rhombencephalitis.

Neurotropic Lineage III Strains of Listeria monocytogenes Disseminate to the Brain without Reaching High Titer in the Blood.

is thought to colonize the brain using one of three mechanisms: direct invasion of the blood-brain barrier, transportation across the barrier by infected monocytes, and axonal migration to the brain stem. The first two pathways seem to occur following unrestricted bacterial growth in the blood and thus have been linked to immunocompromise. In contrast, cell-to-cell spread within nerves is thought to be mediated by a particular subset of neurotropic strains.

Enrichment of Neutrophils and Monocytes From the Liver Following Either Oral or Intravenous Listeria monocytogenes Infection.

Listeria monocytogenes is a foodborne pathogen that causes serious, often deadly, systemic disease in susceptible individuals such as neonates and the elderly. These facultative intracellular bacteria have been an invaluable tool in immunology research for more than three decades. Intravenous (i.

Extracellular electron transfer powers flavinylated extracellular reductases in Gram-positive bacteria.

Mineral-respiring bacteria use a process called extracellular electron transfer to route their respiratory electron transport chain to insoluble electron acceptors on the exterior of the cell. We recently characterized a flavin-based extracellular electron transfer system that is present in the foodborne pathogen , as well as many other Gram-positive bacteria, and which highlights a more generalized role for extracellular electron transfer in microbial metabolism. Here we identify a family of putative extracellular reductases that possess a conserved posttranslational flavinylation modification.

Innate and Adaptive Immune Responses during Infection.

It could be argued that we understand the immune response to infection with better than the immunity elicited by any other bacteria. are Gram-positive bacteria that are genetically tractable and easy to cultivate , and the mouse model of intravenous (i.v.

Prostaglandin E Inhibits the Ability of Neutrophils to Kill .

PGE is a lipid-signaling molecule with complex roles in both homeostasis and inflammation. Depending on the cellular context, PGE may also suppress certain immune responses. In this study, we tested whether PGE could inhibit bacterial killing by polymorphonuclear neutrophils (PMN) using a mouse model of foodborne listeriosis.

Neutrophils from Both Susceptible and Resistant Mice Efficiently Kill Opsonized Listeria monocytogenes.

Inbred mouse strains differ in their susceptibility to infection with the facultative intracellular bacterium , largely due to delayed or deficient innate immune responses. Previous antibody depletion studies suggested that neutrophils (polymorphonuclear leukocytes [PMN]) were particularly important for clearance in the liver, but the ability of PMN from susceptible and resistant mice to directly kill has not been examined. In this study, we showed that PMN infiltrated the livers of BALB/c/By/J (BALB/c) and C57BL/6 (B6) mice in similar numbers and that both cell types readily migrated toward leukotriene B4 in an chemotaxis assay.

A Comparison of Oral and Intravenous Mouse Models of Listeriosis.

is one of several enteric microbes that is acquired orally, invades the gastric mucosa, and then disseminates to peripheral tissues to cause systemic disease in humans. Intravenous (i.v.

Comparison between Listeria sensu stricto and Listeria sensu lato strains identifies novel determinants involved in infection.

The human pathogen L. monocytogenes and the animal pathogen L. ivanovii, together with four other species isolated from symptom-free animals, form the "Listeria sensu stricto" clade.

Replicate in Bone Marrow-Derived CD11c Cells but Not in Dendritic Cells Isolated from the Murine Gastrointestinal Tract.

Recent fate-mapping studies and gene-expression profiles suggest that commonly used protocols to generate bone marrow-derived cultured dendritic cells yield a heterogeneous mixture, including some CD11c cells that may not have a bona fide counterpart in vivo. In this study, we provide further evidence of the discordance between ex vivo-isolated and in vitro-cultured CD11c cells by analyzing an additional phenotype, the ability to support cytosolic growth of the facultative intracellular bacterial pathogen Two days after foodborne infection of mice with GFP-expressing , a small percentage of CD103 and CD103 conventional dendritic cells (cDC) in the intestinal lamina propria and mesenteric lymph nodes were GFP However, in vitro infection of the same subsets of cells harvested from naive mice resulted in inefficient invasion by the bacteria (<0.1% of the inoculum).

Monocytes Are the Predominant Cell Type Associated with in the Gut, but They Do Not Serve as an Intracellular Growth Niche.

After foodborne transmission of the facultative intracellular bacterial pathogen , most of the bacterial burden in the gut is extracellular. However, we previously demonstrated that intracellular replication in an as yet unidentified cell type was essential for dissemination and systemic spread of In this article, we show that the vast majority of cell-associated in the gut were adhered to Ly6C monocytes, a cell type that inefficiently internalized With bone marrow-derived in vitro cultures, high multiplicity of infection or the use of opsonized bacteria enhanced uptake of in CD64 monocytes, but very few bacteria reached the cell cytosol. Surprisingly, monocytes that had upregulated CD64 expression in transition toward becoming macrophages fully supported intracellular growth of In contrast, inflammatory monocytes that had increased CD64 expression in the bone marrow of BALB/c/By/J mice prior to exposure in the gut did not support growth.

Type I IFN Does Not Promote Susceptibility to Foodborne Listeria monocytogenes.

Type I IFN (IFN-α/β) is thought to enhance growth of the foodborne intracellular pathogen Listeria monocytogenes by promoting mechanisms that dampen innate immunity to infection. However, the type I IFN response has been studied primarily using methods that bypass the stomach and, therefore, fail to replicate the natural course of L. monocytogenes infection.

Intracellular Listeria monocytogenes comprises a minimal but vital fraction of the intestinal burden following foodborne infection.

Listeria monocytogenes is a highly adaptive bacterium that replicates as a free-living saprophyte in the environment as well as a facultative intracellular pathogen that causes invasive foodborne infections. The intracellular life cycle of L. monocytogenes is considered to be its primary virulence determinant during mammalian infection; however, the proportion of L.

Cyclic di-GMP-dependent signaling pathways in the pathogenic Firmicute Listeria monocytogenes.

We characterized key components and major targets of the c-di-GMP signaling pathways in the foodborne pathogen Listeria monocytogenes, identified a new c-di-GMP-inducible exopolysaccharide responsible for motility inhibition, cell aggregation, and enhanced tolerance to disinfectants and desiccation, and provided first insights into the role of c-di-GMP signaling in listerial virulence. Genome-wide genetic and biochemical analyses of c-di-GMP signaling pathways revealed that L. monocytogenes has three GGDEF domain proteins, DgcA (Lmo1911), DgcB (Lmo1912) and DgcC (Lmo2174), that possess diguanylate cyclase activity, and three EAL domain proteins, PdeB (Lmo0131), PdeC (Lmo1914) and PdeD (Lmo0111), that possess c-di-GMP phosphodiesterase activity.

Animal models for oral transmission of Listeria monocytogenes.

Listeria monocytogenes has been recognized as a food borne pathogen in humans since the 1980s, but we still understand very little about oral transmission of L. monocytogenes or the host factors that determine susceptibility to gastrointestinal infection, due to the lack of an appropriate small animal model of oral listeriosis. Early feeding trials suggested that many animals were highly resistant to oral infection, and the more reproducible intravenous or intraperitoneal routes of inoculation soon came to be favored.

Fecal transplantation does not transfer either susceptibility or resistance to food borne listeriosis in C57BL/6 and BALB/c/By mice.

The composition of the intestinal microbiota has wide reaching effects on the health of an individual, including the development of protective innate immune responses.  In this report, a fecal transplantation approach was used to determine whether resistance to food borne listeriosis was dependent on the murine gut microbiota.  Transplantation of BALB/c/By feces did not increase the susceptibility of C57BL/6 mice to Listeria monocytogenes infection.

A mouse model of foodborne Listeria monocytogenes infection.

Listeria monocytogenes causes foodborne disease in humans that ranges in severity from mild, self-limiting gastroenteritis to life-threatening systemic infections of the blood, brain, or placenta. The most commonly used animal model of listeriosis is intravenous infection of mice. This systemic model is highly reproducible, and thus, useful for studying cell-mediated immune responses against an intracellular bacterial pathogen, but it completely bypasses the gastrointestinal phase of L.

Listeria monocytogenes: cultivation and laboratory maintenance.

This unit describes general procedures for the lab cultivation and storage of the Gram-positive facultative intracellular bacterium Listeria monocytogenes. The basic protocols are relevant for a wide scope of applications including microbial genetics and both in vitro and in vivo infection studies. Commonly used L.

Oral transmission of Listeria monocytogenes in mice via ingestion of contaminated food.

L. monocytogenes are facultative intracellular bacterial pathogens that cause food borne infections in humans. Very little is known about the gastrointestinal phase of listeriosis due to the lack of a small animal model that closely mimics human disease.