This work was supported by Public Health Service grants AI41816 and AI099339 (N.E.F.) and by F31AI094886-01 (P.D.M.) from NIAID. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the funding sources.

<ol>
	<li>Freitag, N. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+hot+dogs+to+host+cells:+how+the+bacterial+pathogen+Listeria+monocytogenes+regulates+virulence+gene+expression.">From hot dogs to host cells: how the bacterial pathogen Listeria monocytogenes regulates virulence gene expression.</a> Future Microbiol. 1, 89-101 (2006).</li><li>Drevets, D. A., Bronze, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Listeria+monocytogenes:+epidemiology,+human+disease,+and+mechanisms+of+brain+invasion.">Listeria monocytogenes: epidemiology, human disease, and mechanisms of brain invasion.</a> FEMS Immunol Med Microbiol. 53, 151-165 (2008).</li><li>Farber, J. M., Peterkin, P. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Listeria+monocytogenes.+a+food-borne+pathogen.">Listeria monocytogenes. a food-borne pathogen.</a> Microbiol. Rev. 55, 476-511 (1991).</li><li>Lecuit, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Understanding+how+Listeria+monocytogenes+targets+and+crosses+host+barriers.">Understanding how Listeria monocytogenes targets and crosses host barriers.</a> Clin Microbiol Infect. 11, 430-436 (2005).</li><li>Lecuit, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+listeriosis+and+animal+models.">Human listeriosis and animal models.</a> Microbes Infect. 9, 1216-1225 (2007).</li><li>Bou Ghanem, E. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=InlA+promotes+dissemination+of+Listeria+monocytogenes+to+the+mesenteric+lymph+nodes+during+food+borne+infection+of+mice.">InlA promotes dissemination of Listeria monocytogenes to the mesenteric lymph nodes during food borne infection of mice.</a> PLoS Pathog. 8, e1003015 (2012).</li><li>Melton-Witt, J. A., Rafelski, S. M., Portnoy, D. A., Bakardjiev, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oral+infection+with+signature-tagged+Listeria+monocytogenes+reveals+organ-specific+growth+and+dissemination+routes+in+guinea+pigs.">Oral infection with signature-tagged Listeria monocytogenes reveals organ-specific growth and dissemination routes in guinea pigs.</a> Infect Immun. 80, 720-732 (2012).</li><li>Alonzo, F., Bobo, L. D., Skiest, D. J., Freitag, N. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+subpopulations+of+Listeria+monocytogenes+with+enhanced+invasion+of+cardiac+cells.">Evidence for subpopulations of Listeria monocytogenes with enhanced invasion of cardiac cells.</a> J Med Microbiol. , (2011).</li><li>Adler, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammatory+pseudotumor+of+the+heart+caused+by+Listeria+monocytogenes+infection.">Inflammatory pseudotumor of the heart caused by Listeria monocytogenes infection.</a> J Infect. 58, 161-163 (2009).</li><li>Antolin, J., Gutierrez, A., Segoviano, R., Lopez, R., Ciguenza, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endocarditis+due+to+Listeria:+description+of+two+cases+and+review+of+the+literature.">Endocarditis due to Listeria: description of two cases and review of the literature.</a> Eur J Intern Med. 19, 295-296 (2008).</li><li>Brouqui, P., Raoult, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endocarditis+due+to+rare+and+fastidious+bacteria.">Endocarditis due to rare and fastidious bacteria.</a> Clin Microbiol Rev. 14, 177-207 (2001).</li><li>Brusch, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+infections+in+the+immunosuppressed+patient.">Cardiac infections in the immunosuppressed patient.</a> Infect Dis Clin North Am. 15, 613-638 (2001).</li><li>McCue, M. J., Moore, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocarditis+with+microabscess+formation+caused+by+Listeria+monocytogenes+associated+with+myocardial+infarct.">Myocarditis with microabscess formation caused by Listeria monocytogenes associated with myocardial infarct.</a> Hum Pathol. 10, 469-472 (1979).</li><li>Menard, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+L-type+calcium+channel+expression+during+retinoic+acid-induced+differentiation+of+H9C2+cardiac+cells.">Modulation of L-type calcium channel expression during retinoic acid-induced differentiation of H9C2 cardiac cells.</a> J Biol Chem. 274, 29063-29070 (1999).</li><li>Czuprynski, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Listeria+monocytogenes:+silage,+sandwiches+and+science.">Listeria monocytogenes: silage, sandwiches and science.</a> Anim Health Res Rev. 6, 211-217 (2005).</li><li>Grundler, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+surface+proteins+InlA+and+InlB+are+interdependently+required+for+polar+basolateral+invasion+by+Listeria+monocytogenes+in+a+human+model+of+the+blood-cerebrospinal+fluid+barrier.">The surface proteins InlA and InlB are interdependently required for polar basolateral invasion by Listeria monocytogenes in a human model of the blood-cerebrospinal fluid barrier.</a> Microbes Infect. 15, 291-301 (2013).</li><li>Zeldovich, V. B., Robbins, J. R., Kapidzic, M., Lauer, P., Bakardjiev, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Invasive+extravillous+trophoblasts+restrict+intracellular+growth+and+spread+of+Listeria+monocytogenes.">Invasive extravillous trophoblasts restrict intracellular growth and spread of Listeria monocytogenes.</a> PLoS Pathog. 7, e1002005 (2011).</li><li>Kimes, B. W., Brandt, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Properties+of+a+clonal+muscle+cell+line+from+rat+heart.">Properties of a clonal muscle cell line from rat heart.</a> Experimental cell research. 98, 367-381 (1976).</li><li>McMullen, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome+sequence+of+Listeria+monocytogenes+07PF0776,+a+cardiotropic+serovar+4b+strain.">Genome sequence of Listeria monocytogenes 07PF0776, a cardiotropic serovar 4b strain.</a> J Bacteriol. 194, 3552 (2012).</li></ol>

The authors report no competing financial interests.

L. monocytogenes is a widespread and well-characterized human pathogen, capable of causing a number of different disease manifestations15. The bacterium has been previously described for its ability to translocate across barriers, such as the blood-brain-barrier and placental-fetal barriers, in order to reach and colonize the central nervous system and developing fetus, respectively. The in vivo ability of the organism to colonize these tissues is often complemented by an in vitro ab...

Listeria monocytogenes is a Gram-positive intracellular pathogen capable of causing severe disease in susceptible populations, including the elderly, pregnant women, people with HIV/AIDS, and persons receiving chemotherapy1. Infection in these populations is frequently the result of ingesting contaminated food products, and most infections are associated with large-scale food-borne outbreaks2,3. In humans and other mammals, L. monocytogenes is capable of translocating across the epithelial border of the small intestine, thereafter being transported to the liver4,5. Animal models suggest that ingested bacteria replicate within the intestinal villi and transit to the liver through the portal vein or spread via the mesenteric lymph nodes into the blood stream, leading to hematogenous dissemination to the liver and spleen6,7. In the liver and spleen, the bacterium is capable of mediating uptake into both professional phagocytes as well as resident parenchymal cells, and quickly establishes infections within these organs. As bacterial load increases, numerous bacteria are dispersed back into the blood, where they are capable of further colonizing susceptible tissues including the central nervous system and placenta (where present). Colonization of these sites precludes most common manifestations of listeriosis in humans, including meningitis, encephalitis, and fetal abortion2.
Selected subpopulations of L. monocytogenes have been recently shown to have an enhanced capacity to invade and replicate within cardiac tissue8. Manifestations of heart involvement are varied, and range from endocarditis and pericarditis, to fulminant myocarditis complete with conduction abnormalities9-13. The overall number of L. monocytogenes cardiac cases per year is low but may be under estimated as this facet of infection is not generally well recognized. Colonization of the heart by pathogens often requires host predispositions such as pre-existing valvular damage or artificial heart valves. There are, however, isolates of L. monocytogenes that have been identified that are notable for their capacity to colonize the hearts of infected animals in the absence of any cardiac damage and/or abnormalities8.
Herein are described in vitro and in vivo methods for assessing bacterial colonization of cardiac tissue within infected animals using invasion assays in tissue culture as well as live animal infections. These methods have proven useful in not only for identifying strains with the potential to colonize cardiac tissue in infected animals, but should also be useful for the identification of bacterial gene products that serve to enhance cardiac cell invasion and/or result in changes in heart pathology. These methods facilitate the comparison of cardiotropism between multiple strains. For the methods described here, L. monocytogenes 10403S is used as a well-studied representative of a non-cardiotropic strain and the clinical isolate 07PF0776 is used as a representative example of a cardiotropic strain. These two strains were chosen to provide a comparison for bacterial invasion of cardiac cells in vitro and colonization of hearts of infected mice in vivo. The isolate 07PF0776 is a clinical isolate recovered from an interventricular abscess that caused a fatal arrhythmia in an HIV+ patient8. L. monocytogenes isolates may vary in their virulence potential, and given the propensity for Listeria to infect persons with immunosuppression and pregnant women, persons within these populations should exercise caution while assessing different clinical isolates.

<table><tbody><tr><td>Difco</td><td>BHI Broth Base</td><td>237200</td><td>2 kg of Brain Heart Infusion powder (without agar)</td></tr><tr><td>Difco</td><td>Agar</td><td>214510</td><td>2 kg of Granulated Agar</td></tr><tr><td>Difco</td><td>BHI Agar</td><td>241810</td><td>2 kg of Brain Heart Infusion Powder with 7.5% Agar</td></tr><tr><td>in vitrogen</td><td>LB Broth Base</td><td>12975-084</td><td>2 kg of Luria Broth Base Powder (without agar)</td></tr><tr><td>Fisher</td><td>Glass Coverslips</td><td>12-545-80</td><td>12 mm glass coverslips</td></tr><tr><td>Falcon</td><td>24-well Tissue Culture Plate</td><td>35-3047</td><td>24 well, Plasma-treated Tissue Culture Plate</td></tr><tr><td>Falcon</td><td>14mL Polystyrene tube</td><td>352051</td><td>14 ml Polystyrene tubes</td></tr><tr><td>Falcon</td><td>96-well U-bottom plate</td><td>35-3077</td><td>Non-tissue culture treated 96-well plate</td></tr><tr><td>Corning</td><td>0.05% Trypsin, 0.53 mM EDTA (1X)</td><td>25-052-CI</td><td>Stock solution of Trypsin EDTA for tissue culture</td></tr><tr><td>Corning</td><td>DMEM (High glucose, high pyruvate)</td><td>15-013-CU</td><td>DMEM media without FBS, glutamine, or antibiotics</td></tr><tr><td>Corning</td><td>Pen/Strep/Glut Solution</td><td>30-009-CI</td><td>Stock mixture of penicillin, streptomycin, and L-glutamine for tissue culture</td></tr><tr><td>Corning</td><td>Gentamicin</td><td>30-005-CR</td><td>50 mg/ml Stock solution of Gentamicin for tissue culture</td></tr><tr><td>Cellgro (Corning)</td><td>L-Glutamine</td><td>25005197</td><td>Stock L-glutamine solution without antibiotics</td></tr><tr><td>Denville</td><td>75cm^2 Flask</td><td>T1225</td><td>75 cm&lt;sup&gt;2&lt;/sup&gt; tissue culture treated flask</td></tr><tr><td>Denville</td><td>1.5mL microcentrifuge tubes</td><td>2013004</td><td>1.5 ml microcentrifuge tubes</td></tr><tr><td>ATCC</td><td>H9c2 Cardiac Myoblasts</td><td>CRL-1446</td><td>Rat cardiac myoblasts</td></tr><tr><td>Hyclone</td><td>Fetal Bovine Serum</td><td>SH30070.63</td><td>Fetal Bovine Serum</td></tr></tbody></table>

assessing bacterial invasion of cardiac cells in culture and heart colonization in infected mice using listeria monocytogenes

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised patients, the elderly, and pregnant women. The most common manifestations of listeriosis in humans include meningitis, encephalitis, and fetal abortion. A significant but much less documented sequelae of invasive L. monocytogenes infection involves the heart. The death rate from cardiac illness can be up to 35% despite treatment, however very little is known regarding L. monocytogenes colonization of cardiac tissue and its resultant pathologies. In addition, it has recently become apparent that subpopulations of L. monocytogenes have an enhanced capacity to invade and grow within cardiac tissue. This protocol describes in detail in vitro and in vivo methods that can be used for assessing cardiotropism of L. monocytogenes isolates. Methods are presented for the infection of H9c2 rat cardiac myoblasts in tissue culture as well as for the determination of bacterial colonization of the hearts of infected mice. These methods are useful not only for identifying strains with the potential to colonize cardiac tissue in infected animals, but may also facilitate the identification of bacterial gene products that serve to enhance cardiac cell invasion and/or drive changes in heart pathology. These methods also provide for the direct comparison of cardiotropism between multiple L. monocytogenes strains.

Selected isolates of L. monocytogenes exhibit enhanced invasion of cardiac cells in cell culture and in mouse models of infection. Figure 1 shows an example of how bacterial colonies may appear following spot plating of suspensions on agar media. This method allows accurate assessment of CFUs within a sample without using large numbers of agar media plates. Figure 2 shows an example of a tissue culture-based assay comparing the ability of strain 10403S to invade heart cells with...

Watch this Scientific Journal Video about Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes at JoVE.com

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes causes fetal infections in pregnant women and meningitis in susceptible populations. Subpopulations of bacteria can colonize cardiac tissue, causing myocarditis in patients and laboratory animals. Here we present a protocol that describes how to assess L. monocytogenes cardiac cell invasion in vitro and cardiac colonization in infected animals.

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised ...

assessing-bacterial-invasion-cardiac-cells-culture-heart-colonization

Research

JoVE Journal

Immunology and Infection

5.4K Views.  College of Medicine, University of Illinois at Chicago. Listeria monocytogenes veroorzaakt foetale infecties bij zwangere vrouwen en meningitis bij gevoelige populaties. Subpopulaties van bacteriën kunnen hartweefsel koloniseren, waardoor myocarditis ontstaat bij patiënten en proefdieren. Hier presenteren we een protocol dat beschrijft hoe L. monocytogenes cardiale celinvasie in vitro en cardiale kolonisatie bij geïnfecteerde dieren te beoordelen. 

Video: Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Invasion of Human Cells by a Bacterial Pathogen

Here we will describe how we study the invasion of human endothelial cells by bacterial pathogen Staphylococcus aureus . The general protocol can be applied to the study of cell invasion by virtually any culturable bacterium. The stages at which specific aspects of invasion can be studied, such as the role of actin rearrangement or caveolae, will be highlighted. Host cells are grown in flasks and when ready for use are seeded into 24-well plates containing Thermanox coverslips. Using coverslips allows subsequent removal of the cells from the wells to reduce interference from serum proteins deposited onto the sides of the wells (to which S. aureus would attach). Bacteria are grown to the required density and washed to remove any secreted proteins (e.g. toxins). Coverslips with confluent layers of endothelial cells are transferred to new 24-well plates containing fresh culture medium before the addition of bacteria. Bacteria and cells are then incubated together for the required amount of time in 5% CO2 at 37&deg;C. For S. aureus this is typically between 15-90 minutes. Thermanox coverslips are removed from each well and dip-washed in PBS to remove unattached bacteria. If total associated bacteria (adherent and internalised) are to be quantified, coverslips are then placed in a fresh well containing 0.5% Triton X-100 in PBS. Gentle pipetting leads to complete cell lysis and bacteria are enumerated by serial dilution and plating onto agar. If the number of bacteria that have invaded the cells is needed, coverslips are added to wells containing 500 &mu;l tissue culture medium supplemented with gentamicin and incubation continued for 1 h, which will kill all external bacteria. Coverslips can then be washed, cells lysed and bacteria enumerated by plating onto agar as described above. If the experiment requires direct visualisation, coverslips can be fixed and stained for light, fluorescence or confocal microscopy or prepared for electron microscopy.

A general protocol for the study of invasion of host cells by a bacterial pathogen, focusing on Staphylococcus aureus and human endothelial cells.

Here we will describe how we study the invasion of human endothelial cells by bacterial pathogen Staphylococcus aureus . The general protocol can be ...

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of Listeria, which results in systemic infection2. After injection, Listeria quickly disseminates to the spleen and liver due to uptake by CD8&alpha;+ dendritic cells and Kupffer cells3,4. Once phagocytosed, various bacterial proteins enable Listeria to escape the phagosome, survive within the cytosol, and infect neighboring cells5. During the first three days of infection, different innate immune cells (e.g. monocytes, neutrophils, NK cells, dendritic cells) mediate bactericidal mechanisms that minimize Listeria proliferation. CD8+ T cells are subsequently recruited and responsible for the eventual clearance of Listeria from the host, typically within 10 days of infection6.
Successful clearance of Listeria from infected mice depends on the appropriate onset of host immune responses6	. There is a broad range of sensitivities amongst inbred mouse strains7,8. Generally, mice with increased susceptibility to Listeria infection are less able to control bacterial proliferation, demonstrating increased bacterial load and/or delayed clearance compared to resistant mice. Genetic studies, including linkage analyses and knockout mouse strains, have identified various genes for which sequence variation affects host responses to Listeria infection6,8-14. Determination and comparison of infection kinetics between different mouse strains is therefore an important method for identifying host genetic factors that contribute to immune responses against Listeria. Comparison of host responses to different Listeria strains is also an effective way to identify bacterial virulence factors that may serve as potential targets for antibiotic therapy or vaccine design.
We describe here a straightforward method for measuring bacterial load (colony forming units [CFU] per tissue) and preparing single-cell suspensions of the liver and spleen for FACS analysis of immune responses in Listeria-infected mice. This method is particularly useful for initial characterization of Listeria infection in novel mouse strains, as well as comparison of immune responses between different mouse strains infected with Listeria. We use the Listeria monocytogenes EGD strain15 that, when cultured on blood agar, exhibits a characteristic halo zone around each colony due to &beta;-hemolysis1 (Figure 1). Bacterial load and immune responses can be determined at any time-point after infection by culturing tissue homogenate on blood agar plates and preparing tissue cell suspensions for FACS analysis using the protocols described below. We would note that individuals who are immunocompromised or pregnant should not handle Listeria, and the relevant institutional biosafety committee and animal facility management should be consulted before work commences.

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes is a model organism for studying immune responses and genetic susceptibility to intracellular bacteria in mice. This method enables one to measure bacterial load and generate single-cell suspensions of the liver and spleen from mice for FACS analysis to determine changes in immune cells due to Listeria infection.

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of ...

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. This paper describes a novel mouse model for oral transmission of L. monocytogenes. Using this model, mice fed L. monocytogenes-contaminated bread have a discrete phase of gastrointestinal infection, followed by varying degrees of systemic spread in susceptible (BALB/c/By/J) or resistant (C57BL/6) mouse strains. During the later stages of the infection, dissemination to the gall bladder and brain is observed. The food borne model of listeriosis is highly reproducible, does not require specialized skills, and can be used with a wide variety of bacterial isolates and laboratory mouse strains. As such, it is the ideal model to study both virulence strategies used by L. monocytogenes to promote intestinal colonization, as well as the host response to invasive food borne bacterial infection.

Oral Transmission of Listeria monocytogenes in Mice via Ingestion of Contaminated Food

This paper describes a novel method for oral infection of mice using Listeria monocytogenes-contaminated food. The protocol can readily be adapted for use with other food borne bacterial pathogens.

L. monocytogenes are facultative intracellular bacterial pathogens that cause food borne infections in humans. Very little is known about the ...

Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Bacterial intracellular pathogens can be conceived as molecular tools to dissect cellular signaling cascades due to their capacity to exquisitely manipulate and subvert cell functions which are required for the infection of host target tissues. Among these bacterial pathogens, Listeria monocytogenes is a Gram positive microorganism that has been used as a paradigm for intracellular parasitism in the characterization of cellular immune responses, and which has played instrumental roles in the discovery of molecular pathways controlling cytoskeletal and membrane trafficking dynamics. In this article, we describe a robust microscopical assay for the detection of late cellular infection stages of L. monocytogenes based on the fluorescent labeling of InlC, a secreted bacterial protein which accumulates in the cytoplasm of infected cells; this assay can be coupled to automated high-throughput small interfering RNA screens in order to characterize cellular signaling pathways involved in the up- or down-regulation of infection.

Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Listeria monocytogenes is a Gram positive bacterial pathogen frequently used as a major model for the study of intracellular parasitism. Imaging late L. monocytogenes infection stages within the context of small-interfering RNA screens allows for the global study of cellular pathways required for bacterial infection of target host cells.

Bacterial intracellular  pathogens can be conceived as molecular tools to dissect cellular signaling  cascades due to their capacity to exquisitely ...

Experimental Infection with Listeria monocytogenes as a Model for Studying Host Interferon-&#947; Responses

L. monocytogenes is a gram-positive bacterium that is a cause of food borne disease in humans. Experimental infection of mice with this pathogen has been highly informative on the role of innate and adaptive immune cells and specific cytokines in host immunity against intracellular pathogens. Production of IFN-&#947; by innate cells during sublethal infection with L. monocytogenes is important for activating macrophages and early control of the pathogen1-3. In addition, IFN-&#947; production by adaptive memory lymphocytes is important for priming the activation of innate cells upon reinfection4. The L. monocytogenes infection model thus serves as a great tool for investigating whether new therapies that are designed to increase IFN-&#947; production have an impact on IFN-&#947; responses in vivo and have productive biological effects such as increasing bacterial clearance or improving mouse survival from infection. Described here is a basic protocol for how to conduct intraperitoneal infections of C57BL/6J mice with the EGD strain of L. monocytogenes and to measure IFN-&#947; production by NK cells, NKT cells, and adaptive lymphocytes by flow cytometry. In addition, procedures are described to: (1) grow and prepare the bacteria for inoculation, (2) measure bacterial load in the spleen and liver, and (3) measure animal survival to endpoints. Representative data are also provided to illustrate how this infection model can be used to test the effect of specific agents on IFN-&#947; responses to L. monocytogenes and survival of mice from this infection.

This protocol describes how to inoculate C57BL/6J mice with the EGD strain of Listeria monocytogenes (L. monocytogenes) and to measure interferon-&#947; (IFN-&#947;) responses by natural killer (NK) cells, natural killer T (NKT) cells, and adaptive T lymphocytes post-infection. This protocol also describes how to conduct survival studies in mice after infection with a modified LD50 dose of the pathogen.

L. monocytogenes is a gram-positive bacterium that is a cause of food borne disease in humans. Experimental infection of mice with this pathogen has been ...

Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling

During bacteremia Streptococcus pneumoniae can translocate across the vascular endothelium into the myocardium and form discrete bacteria-filled microscopic lesions (microlesions) that are remarkable due to the absence of infiltrating immune cells. Due to their release of cardiotoxic products, S. pneumoniae within microlesions are thought to contribute to the heart failure that is frequently observed during fulminate invasive pneumococcal disease in adults. Herein is demonstrated a protocol for experimental mouse infection that leads to reproducible cardiac microlesion formation within 30 hr. Instruction is provided on microlesion identification in hematoxylin &#38; eosin stained heart sections and the morphological distinctions between early and late microlesions are highlighted. Instruction is provided on a protocol for verification of S. pneumoniae within microlesions using antibodies against pneumococcal capsular polysaccharide and immunofluorescent microscopy. Last, a protocol for antibiotic intervention that rescues infected mice and for the detection and assessment of scar formation in the hearts of convalescent mice is provided. Together, these protocols will facilitate the investigation of the molecular mechanisms underlying pneumococcal cardiac invasion, cardiomyocyte death, cardiac remodeling as a result of exposure to S. pneumoniae, and the immune response to the pneumococci in the heart.

Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling

Streptococcus pneumoniae forms discrete non-purulent microscopic lesions in the heart. Outlined is the protocol for a murine model of cardiac microlesion formation. Instruction is provided on microlesion visualization using microscopy, discrimination between early and late microlesions, and methods to detect cardiac remodeling in hearts of convalescent animals.

During bacteremia Streptococcus pneumoniae can translocate across the vascular endothelium into the myocardium and form discrete bacteria-filled ...

Medicine

Listeria monocytogenes Infection of the Brain

Listeria monocytogenes is an intracellular bacterial pathogen that is frequently associated with food-borne infection. The ability of&#160;L. monocytogenes to cross the blood-brain barrier (BBB) is concerning as it can lead to life-threatening meningitis and encephalitis. The BBB protects the brain microenvironment from various toxic metabolites and microbial pathogens found in the blood following infection, and therefore supports brain homeostasis. The mechanisms by which L. monocytogenes present in the bloodstream cross the BBB to cause brain infections are not fully understood and there is also a lack of a robust model system to study brain infections by L. monocytogenes. Here, we present a simple mouse infection model to determine whether bacteria have crossed the BBB and to quantitate the burden of bacteria that have colonized the brain in vivo. In this method, animals were infected intravenously with L. monocytogenes and were humanely euthanized by exposure to CO2 followed by cervical dislocation. Cardiac perfusion of the animals was performed prior to harvesting infected organs. Blood was collected before perfusion and the number of bacteria per organ or mL of blood was determined by plating dilutions of the blood or organ homogenates on agar plates and counting the number of colonies formed. This method can be used to study novel receptor-ligand interactions that enhance infection of the brain by L. monocytogenes and can be easily adapted for the study of multiple bacterial pathogens.

Listeria monocytogenes Infection of the Brain

During infection, Listeria monocytogenes is capable of crossing the blood-brain barrier to colonize the brain. In this protocol, we demonstrate how to assess bacterial colonization of organs following infection of mice. A procedure to perform whole organ perfusion for specific determination of bacterial numbers in the brain parenchyma is provided.

Listeria monocytogenes is an intracellular bacterial pathogen that is frequently associated with food-borne infection. The ability of&#160;L. ...

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses

There are a variety of strategies bacterial pathogens employ to survive and proliferate once inside the eukaryotic cell. The so-called 'cytosolic' pathogens (Listeria monocytogenes, Shigella flexneri, Burkholderia pseudomallei, Francisella tularensis, and Rickettsia spp.) gain access to the infected cell cytosol by physically and enzymatically degrading the primary vacuolar membrane. Once in the cytosol, these pathogens both proliferate as well as generate sufficient mechanical forces to penetrate the plasma membrane of the host cell in order to infect new cells. Here, we show how this terminal step of the cellular infection cycle of L. monocytogenes (Lm) can be quantified by both colony-forming unit assays and flow cytometry and give examples of how both pathogen- and host-encoded factors impact this process. We also show a close correspondence of Lm infection dynamics of cultured cells infected in vitro and those of hepatic cells derived from mice infected in vivo. These function-based assays are relatively simple and can be readily scaled up for discovery-based high-throughput screens for modulators of eukaryotic cell function.

We describe both in vitro and in vivo infection assays that can be used to analyze the activities of host-encoding factors.

There are a variety of strategies bacterial pathogens employ to survive and proliferate once inside the eukaryotic cell. The so-called 'cytosolic' ...

A Technique to Establish a Bacterial Infection Model in an Ex Vivo Organ Culture

Source: Rizzuto, G. A., et al. <a href="https://app.jove.com/v/54237">Human Placental and Decidual Organ Cultures to Study Infections at the Maternal-fetal Interface.</a> J. Vis. Exp. (2016)
This video demonstrates a method to establish an infection model in placental tissues to study infection propagation. An ex vivo placental organ culture is infected with Listeria monocytogenes, a facultative intracellular parasite. The bacteria invade extravillous trophoblasts (EVTs) to enter the placental tissue and then propagate to other cells via cell-to-cell spread.

All procedures involving human participants have been performed in compliance with the institutional, national, and international guidelines for human ...

JoVE Encyclopedia of Experiments

Immunology

Immunopathology

In Vitro Models

Assessing Bacterial Colonization in a Mouse Brain following Listeria monocytogenes Infection

Source: Ghosh, P., et al., <a href="https://app.jove.com/v/58723">Listeria monocytogenes Infection of the Brain.</a> J. Vis. Exp. (2018)
This video demonstrates the quantification of the infective bacterial load from the perfused mouse brain infected with Listeria monocytogenes.

All procedures involving animal samples have been reviewed and approved by the appropriate animal ethical review committee.&#160;
1. Organ Harvesting and ...

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Samenvatting

Meer video's verkennen