This work was supported by institutional funds to C.M.R.

<ol>
	<li>Qazi, S. A., Stoll, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neonatal+sepsis:+a+major+global+public+health+challenge.">Neonatal sepsis: a major global public health challenge.</a> Pediatr Infect Dis J. 28, 1-2 (2009).</li><li>Simonsen, K. A., Anderson-Berry, A. L., Delair, S. F., Davies, H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early-onset+neonatal+sepsis.">Early-onset neonatal sepsis.</a> Clinical Microbiology Reviews. 27 (1), 21-47 (2014).</li><li>Seman, B. 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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=Neonatal+macrophages+express+elevated+levels+of+interleukin-27+that+oppose+immune+responses.">Neonatal macrophages express elevated levels of interleukin-27 that oppose immune responses.</a> Immunology. 139 (4), 484-493 (2013).</li><li>Basha, S., Surendran, N., Pichichero, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immune+responses+in+neonates.">Immune responses in neonates.</a> Expert Reviews of Clinical Immunology. 10 (9), 1171-1184 (2014).</li><li>Gleave Parson, M., 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=Murine+myeloid-derived+suppressor+cells+are+a+source+of+elevated+levels+of+interleukin-27+in+early+life+and+compromise+control+of+bacterial+infection.">Murine myeloid-derived suppressor cells are a source of elevated levels of interleukin-27 in early life and compromise control of bacterial infection.</a> Immunology and Cell Biology. 97 (5), 445-446 (2018).</li><li>Adkins, B., Leclerc, C., Marshall-Clarke, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neonatal+adaptive+immunity+comes+of+age.">Neonatal adaptive immunity comes of age.</a> Nature Reviews Immunology. 4 (7), 553-564 (2004).</li><li>Kim, S. K., Keeney, S. E., Alpard, S. K., Schmalstieg, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+L-selectin+and+CD11b+on+neutrophils+of+adults+and+neonates+during+the+first+month+of+life.">Comparison of L-selectin and CD11b on neutrophils of adults and neonates during the first month of life.</a> Pediatrics Research. 53 (1), 132-136 (2003).</li><li>Velilla, P. A., Rugeles, M. T., Chougnet, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defective+antigen-presenting+cell+function+in+human+neonates.">Defective antigen-presenting cell function in human neonates.</a> Clinical Immunology. 121 (3), 251-259 (2006).</li><li>Le Garff-Tavernier, M., 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=Human+NK+cells+display+major+phenotypic+and+functional+changes+over+the+life+span.">Human NK cells display major phenotypic and functional changes over the life span.</a> Aging Cell. 9 (4), 527-535 (2010).</li><li>Weinberger, B., 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=Mechanisms+underlying+reduced+responsiveness+of+neonatal+neutrophils+to+distinct+chemoattractants.">Mechanisms underlying reduced responsiveness of neonatal neutrophils to distinct chemoattractants.</a> Journal of Leukocyte Biology. 70 (6), 969-976 (2001).</li><li>Gabrilovich, D. 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(125), e55796 (2017).</li><li>Bayarmagnai, B., Perrin, L., Esmaeili Pourfarhangi, K., Gligorijevic, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravital+Imaging+of+Tumor+Cell+Motility+in+the+Tumor+Microenvironment+Context.">Intravital Imaging of Tumor Cell Motility in the Tumor Microenvironment Context.</a> Methods in Molecular Biology. 1749, 175-193 (2018).</li><li>Beerling, E., Ritsma, L., Vrisekoop, N., Derksen, P. W., van Rheenen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravital+microscopy:+new+insights+into+metastasis+of+tumors.">Intravital microscopy: new insights into metastasis of tumors.</a> Journal of Cell Science. 124, 299-310 (2011).</li><li>Witcomb, L. A., Collins, J. W., McCarthy, A. J., Frankel, G., Taylor, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioluminescent+Imaging+Reveals+Novel+Patterns+of+Colonization+and+Invasion+in+Systemic+Escherichia+coli+K1+Experimental+Infection+in+the+Neonatal+Rat.">Bioluminescent Imaging Reveals Novel Patterns of Colonization and Invasion in Systemic Escherichia coli K1 Experimental Infection in the Neonatal Rat.</a> Infection and Immunity. 83 (12), 4528 (2015).</li><li>Singh, K., 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=Inter-alpha+inhibitor+protein+administration+improves+survival+from+neonatal+sepsis+in+mice.">Inter-alpha inhibitor protein administration improves survival from neonatal sepsis in mice.</a> Pediatric Research. 68 (3), 242-247 (2010).</li><li>Pluschke, G., Pelkonen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+factors+in+the+resistance+of+newborn+mice+to+K1+Escherichia+coli+infection.">Host factors in the resistance of newborn mice to K1 Escherichia coli infection.</a> Microb. Patho. , 93-102 (1988).</li><li>Mancuso, G., 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=Role+of+interleukin+12+in+experimental+neonatal+sepsis+caused+by+group+B+streptococci.">Role of interleukin 12 in experimental neonatal sepsis caused by group B streptococci.</a> Infections and Immunity. 65 (9), 3731-3735 (1997).</li><li>Thammavongsa, V., Rauch, S., Kim, H. K., Missiakas, D. M., Schneewind, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+A-neutralizing+monoclonal+antibody+protects+neonatal+mice+against+Staphylococcus+aureus.">Protein A-neutralizing monoclonal antibody protects neonatal mice against Staphylococcus aureus.</a> Vaccine. 33 (4), 523-526 (2015).</li><li>Andrade, E. B., 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=TLR2-induced+IL-10+production+impairs+neutrophil+recruitment+to+infected+tissues+during+neonatal+bacterial+sepsis.">TLR2-induced IL-10 production impairs neutrophil recruitment to infected tissues during neonatal bacterial sepsis.</a> Journal of Immunology. 191 (9), 4759-4768 (2013).</li></ol>

The authors have no conflicts of interest to disclose.

Our subscapular infection model for inducing bacterial sepsis in neonatal mice is a novel method to study the longitudinal spread of bacterial pathogens in real time. Intravital imaging provides the opportunity to explore bacterial dissemination in real time in neonates. This is critical to understand the kinetics of bacterial dissemination and to further study the host response and damage at the appropriate phase of disease. Mouse pups are administered a subcutaneous, subscapular injection of bacterial inoculum. This in...

Bacterial sepsis is a significant concern for neonates that exhibit a unique immune profile in the first days of life that does not provide adequate protection from infection1. Neonatal sepsis continues to be a significant U.S. healthcare problem accounting for greater than 75,000 cases annually in the U.S alone2. To study these infections in depth, novel animal models that recapitulate aspects of human disease are required. We have established a neonatal mouse infection model using Escherichia coli, O1:K1:H73. E. coli is the second leading cause of neonatal sepsis in the U.S., but responsible for the majority of sepsis-associated mortality4,5. However, it is the leading cause when pre-term and very low birth-weight (VLBW)&#160;babies are considered independently5. The K1 serotype is most frequently associated with invasive bloodstream infections and meningitis in neonates6,7. Currently, there are no other treatment options beyond antibiotics and supportive care. Meanwhile, rates of antibiotic resistance continue to rise for many pathogenic bacteria, with some strains of E. coli resistant to a multitude of antibiotics commonly used in treatment8. Thus, it is imperative that we continue to generate methods to study the mechanisms of sepsis and the host response in neonates. These results can help to improve upon current treatments and infection outcomes.
The immune state of neonates is characterized by both phenotypic and functional differences compared to adults. For instance, elevated levels of anti-inflammatory and regulatory cytokines, such as interleukin (IL)-10 and IL-27, have been shown to be produced by cord blood-derived macrophages and are present at greater levels in the serum of murine neonates9,10,11. This is consistent with lower levels of IFN-&#945;, IFN-&#611;, IL-12, and TNF-&#945; that are frequently reported from neonatal cells compared with adult counterparts10. Additionally, the neonatal immune system is skewed toward a Th2 and regulatory T cell response as compared to adults12. Elevated numbers of neutrophils, T cells, B cells, NK cells, and monocytes are also present in neonates, but with significant functional impairments. This includes defects in expression of cell surface markers and antigen presentation that suggest immaturity13,14,15. Additionally, neonatal neutrophils are significantly deficient in their ability to migrate to chemotactic factors16. Myeloid-derived suppressor cells (MDSCs) are also found at elevated levels in neonates and recently shown to be a source of IL-2711. MDSCs are highly suppressive toward T cells17. Collectively, these data demonstrate limitations in neonatal immunity that lend to increased susceptibility to infection.
To study the progression of the bacterial burden and dissect protective host immune responses during neonatal sepsis, we have developed a novel infection model. Neonatal mice at days 3-4 of life are difficult to inject in the intraperitoneal space or tail vein. In our model, day 3 or 4 pups are administered the bacterial inoculum or PBS subcutaneously into the scapular region. A systemic infection develops and using luminescent E. coli O1:K1:H7, we can longitudinally image individual neonatal mice to follow the disseminated bacterial burden in peripheral tissues. This is the first reported model to utilize intravital imaging to understand the kinetics of dissemination of bacteria during sepsis in murine neonates3.
Here, we describe a protocol to induce septic E. coli infections in neonatal mice3. We describe how to prepare the bacterial inoculum for injection, and how to harvest tissue for assessment of pathology, measurement of inflammatory markers by gene expression analysis, and enumeration of the bacterial burden. In addition, the use of luminescent E. coli for intravital imaging of infected neonates and quantification of bacterial killing by neonatal immune cells is also described. These protocols may also be adapted to study other important bacterial infections in neonates. The data presented here represents an overall novel approach to understanding infection dynamics in a translatable neonatal sepsis model.

<table>
	<tbody>
		<tr>
			<td>1 mL Insulin Syringe</td>
			<td>Coviden</td>
			<td>1188128012</td>
			<td>Inoculum or PBS injection</td>
		</tr>
		<tr>
			<td>10% Neutral Buffered Formalin</td>
			<td>VWR</td>
			<td>89370-094</td>
			<td>Histopathology</td>
		</tr>
		<tr>
			<td>ACK Lysis Buffer</td>
			<td>Gibco</td>
			<td>LSA1049201</td>
			<td>Bacterial clearance assay</td>
		</tr>
		<tr>
			<td>Animal Tattoo Ink Paste</td>
			<td>Ketchum</td>
			<td>KI1482039</td>
			<td>Animal identification</td>
		</tr>
		<tr>
			<td>Animal Tattoo Ink Green Paste</td>
			<td>Ketchum</td>
			<td>KI1471039</td>
			<td>Animal identification</td>
		</tr>
		<tr>
			<td>Anti-Ly-6B.2 Microbeads</td>
			<td>Miltenyi Biotec</td>
			<td>130-100-781</td>
			<td>Cell isolation</td>
		</tr>
		<tr>
			<td>Escherichia coli O1:K1:H7</td>
			<td>ATCC</td>
			<td>11775</td>
			<td></td>
		</tr>
		<tr>
			<td>Escherichia coli O1:K1:H7-lux (expresses luciferase)</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Constructed in-house at WVU</td>
		</tr>
		<tr>
			<td>E.Z.N.A. HP Total Extraction RNA Kit</td>
			<td>Omega Bio-tek</td>
			<td>R6812</td>
			<td>RNA extration</td>
		</tr>
		<tr>
			<td>DPBS, 1X</td>
			<td>Corning</td>
			<td>21-031-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Difco Tryptic Soy Agar</td>
			<td>Becton, Dickinson and Company</td>
			<td>236950</td>
			<td>Bacterial growth</td>
		</tr>
		<tr>
			<td>IL-1 beta Primer/Probe (Mm00434228)</td>
			<td>Thermo Fisher Scientific</td>
			<td>4331182</td>
			<td>Cytokine expression qPCR</td>
		</tr>
		<tr>
			<td>IL-6 Primer/Probe (Mm00446190)</td>
			<td>Thermo Fisher Scientific</td>
			<td>4331182</td>
			<td>Cytokine expression qPCR</td>
		</tr>
		<tr>
			<td>iQ Supermix</td>
			<td>Bio-Rad</td>
			<td>1708860</td>
			<td>Real-time quantitative PCR</td>
		</tr>
		<tr>
			<td>iScript cDNA Synthesis Kit</td>
			<td>Bio-Rad</td>
			<td>1708891</td>
			<td>cDNA synthesis</td>
		</tr>
		<tr>
			<td>Isolation Buffer</td>
			<td>Miltenyi Biotec</td>
			<td>N/A</td>
			<td>Bacterial clearance assay</td>
		</tr>
		<tr>
			<td>IVIS Spectrum CT and Living Image 4.5 Software</td>
			<td>Perkin Elmer</td>
			<td>N/A</td>
			<td>Intravital imaging</td>
		</tr>
		<tr>
			<td>LB Broth, Lennox</td>
			<td>Fisher BioReagents</td>
			<td>BP1427-500</td>
			<td>Bacterial growth</td>
		</tr>
		<tr>
			<td>EASYstrainer (Nylon Basket)</td>
			<td>Greiner Bio-one</td>
			<td>542 040</td>
			<td>Cell strainer</td>
		</tr>
		<tr>
			<td>SpectraMax iD3</td>
			<td>Molecular Devices</td>
			<td>N/A</td>
			<td>Plate reader</td>
		</tr>
		<tr>
			<td>Pellet Pestle Motor</td>
			<td>Grainger</td>
			<td>6HAZ6</td>
			<td>Tissue homogenization</td>
		</tr>
		<tr>
			<td>Polypropylene Pellet Pestles</td>
			<td>Grainger</td>
			<td>6HAY5</td>
			<td>Tissue homogenization</td>
		</tr>
		<tr>
			<td>Prime Thermal Cycler</td>
			<td>Techne</td>
			<td>3PRIMEBASE/02</td>
			<td>cDNA synthesis</td>
		</tr>
		<tr>
			<td>TNF-alpha Primer/Probe (Mm00443258)</td>
			<td>Thermo Fisher Scientific</td>
			<td>4331182</td>
			<td>Cytokine expression qPCR</td>
		</tr>
		<tr>
			<td>TriReagent (GTCP)</td>
			<td>Molecular Research Center</td>
			<td>TR 118</td>
			<td>RNA extration</td>
		</tr>
	</tbody>
</table>

a neonatal imaging model of gram-negative bacterial sepsis

Neonates are at an increased risk of bacterial sepsis due to the unique immune profile they display in the first months of life. We have established a protocol for studying the pathogenesis of E. coli O1:K1:H7, a serotype responsible for high mortality rates in neonates. Our method utilizes intravital imaging of neonatal pups at different time points during the progression of infection. This imaging, paralleled by measurement of bacteria in the blood, inflammatory profiling, and tissue histopathology, signifies a rigorous approach to understanding infection dynamics during sepsis. In the current report, we model two infectious inoculums for comparison of bacterial burdens and severity of disease. We find that subscapular infection leads to disseminated infection by 10 h post-infection. By 24 h, infection of luminescent E. coli was abundant in the blood, lungs, and other peripheral tissues. Expression of inflammatory cytokines in the lungs is significant at 24 h, and this is followed by cellular infiltration and evidence of tissue damage that increases with infectious dose. Intravital imaging does have some limitations. This includes a luminescent signal threshold and some complications that can arise with neonates during anesthesia. Despite some limitations, we find that our infection model offers an insight for understanding longitudinal infection dynamics during neonatal murine sepsis, that has not been thoroughly examined to date. We expect this model can also be adapted to study other critical bacterial infections during early life.

This protocol induced bacterial sepsis in neonatal mice, and we used longitudinal intravital imaging, enumeration of bacteria in the blood, histological assessments of pathology, and inflammatory cytokine expression profiles to study the course of disease. Signs of morbidity were observed in neonatal pups infected with both low (~2 x 106 CFUs) and high (~7 x 106 CFUs) inoculums of E.coli over time. Pups that received the greater inoculum displayed more prominent signs of distress that inclu...

Watch this Scientific Journal Video about A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis at JoVE.com

A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis

Infection of neonatal mice with bioluminescent E. coli O1:K1:H7 results in a septic infection with significant pulmonary inflammation and lung pathology. Here, we describe procedures to model and further study neonatal sepsis using longitudinal intravital imaging in parallel with enumeration of systemic bacterial burdens, inflammatory profiling, and lung histopathology.

Neonates are at an increased risk of bacterial sepsis due to the unique immune profile they display in the first months of life. We have established a ...

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Immunology and Infection

6.2K Views.  West Virginia University School of Medicine. Infection of neonatal mice with bioluminescent E. coli O1:K1:H7 results in a septic infection with significant pulmonary inflammation and lung pathology. Here, we describe procedures to model and further study neonatal sepsis using longitudinal intravital imaging in parallel with enumeration of systemic bacterial burdens, inflammatory profiling, and lung histopathology.

Video: A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis

Colon Ascendens Stent Peritonitis (CASP) - a Standardized Model for Polymicrobial Abdominal Sepsis

Sepsis remains a persistent problem on intensive care units all over the world. Understanding the complex mechanisms of sepsis is the precondition for establishing new therapeutic approaches in this field. Therefore, animal models are required that are able to closely mimic the human disease and also sufficiently deal with scientific questions. The Colon Ascendens Stent Peritonitis (CASP) is a highly standardized model for polymicrobial abdominal sepsis in rodents. In this model, a small stent is surgically inserted into the ascending colon of mice or rats leading to a continuous leakage of intestinal bacteria into the peritoneal cavity. The procedure results in peritonitis, systemic bacteraemia, organ infection by gut bacteria, and systemic but also local release of several pro- and anti-inflammatory cytokines. The lethality of CASP can be controlled by the diameter of the inserted stent. A variant of this model, the so-called CASP with intervention (CASPI), raises opportunity to remove the septic focus by a second operation according to common procedures in clinical practice. CASP is an easily learnable and highly reproducible model that closely mimics the clinical course of abdominal sepsis. It leads way to study on questions in several scientific fields e.g. immunology, infectiology, or surgery.

Colon Ascendens Stent Peritonitis CASP - a Standardized Model for Polymicrobial Abdominal Sepsis

The Colon Ascendens Stent Peritonitis (CASP) is a highly standardized model for polymicrobial abdominal sepsis in rodents. This article describes the surgical procedure of CASP. The CASP model and its variants allow the systematic investigation of various problems concerning the subject of sepsis.

Sepsis remains a persistent problem on intensive care units all over the world. Understanding the complex mechanisms of sepsis is the precondition for ...

Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction

Lipopolysaccharide (LPS) is a major component of Gram-negative bacterial outer membranes. It is a tripartite molecule consisting of lipid A, which is embedded in the outer membrane, a core oligosaccharide and repeating O-antigen units that extend outward from the surface of the cell1, 2. LPS is an immunodominant molecule that is important for the virulence and pathogenesis of many bacterial species, including Pseudomonas aeruginosa, Salmonella species, and Escherichia coli3-5, and differences in LPS O-antigen composition form the basis for serotyping of strains. LPS is involved in attachment to host cells at the initiation of infection and provides protection from complement-mediated killing; strains that lack LPS can be attenuated for virulence6-8. For these reasons, it is important to visualize LPS, particularly from clinical isolates. Visualizing LPS banding patterns and recognition by specific antibodies can be useful tools to identify strain lineages and to characterize various mutants. 
In this report, we describe a hot aqueous-phenol method for the isolation and purification of LPS from Gram-negative bacterial cells. This protocol allows for the extraction of LPS away from nucleic acids and proteins that can interfere with visualization of LPS that occurs with shorter, less intensive extraction methods9. LPS prepared this way can be separated by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and directly stained using carbohydrate/glycoprotein stains or standard silver staining methods. Many anti-sera to LPS contain antibodies that cross-react with outer membrane proteins or other antigenic targets that can hinder reactivity observed following Western immunoblot of SDS-PAGE-separated crude cell lysates. Protease treatment of crude cell lysates alone is not always an effective way of removing this background using this or other visualization methods. Further, extensive protease treatment in an attempt to remove this background can lead to poor quality LPS that is not well resolved by any of the aforementioned methods. For these reasons, we believe that the following protocol, adapted from Westpahl and Jann10, is ideal for LPS extraction.

We describe a modified hot aqueous-phenol extraction method for purifying lipopolysaccharide (LPS) from Gram-negative bacteria. Once extracted, the LPS can be subsequently analyzed by SDS-PAGE and visualized by direct staining or Western immunoblot.

Lipopolysaccharide (LPS)  is a major component of Gram-negative bacterial outer membranes. It is a tripartite molecule consisting of  lipid A, which is ...

Bioluminescent Bacterial Imaging In Vivo

This video describes the use of whole body bioluminesce imaging (BLI) for the study of bacterial trafficking in live mice, with an emphasis on the use of bacteria in gene and cell therapy for cancer. Bacteria present an attractive class of vector for cancer therapy, possessing a natural ability to grow preferentially within tumors following systemic administration. Bacteria engineered to express the lux gene cassette permit BLI detection of the bacteria and concurrently tumor sites. The location and levels of bacteria within tumors over time can be readily examined, visualized in two or three dimensions. The method is applicable to a wide range of bacterial species and tumor xenograft types. This article describes the protocol for analysis of bioluminescent bacteria within subcutaneous tumor bearing mice. Visualization of commensal bacteria in the Gastrointestinal tract (GIT) by BLI is also described. This powerful, and cheap, real-time imaging strategy represents an ideal method for the study of bacteria in vivo in the context of cancer research, in particular gene therapy, and infectious disease. This video outlines the procedure for studying lux-tagged E. coli in live mice, demonstrating the spatial and temporal readout achievable utilizing BLI with the IVIS system.

Bioluminescent Bacterial Imaging In Vivo

This article describes the administration of lux-tagged bacteria to mice and subsequent in vivo analysis using IVIS bioluminescence imaging.

This video describes the use of whole body bioluminesce imaging (BLI) for the study of bacterial trafficking in live mice, with an emphasis on the use of ...

Measurement of Tactile Allodynia in a Murine Model of Bacterial Prostatitis

Uropathogenic Escherichia coli (UPEC) are pathogens that play an important role in urinary tract infections and bacterial prostatitis1. We have recently shown that UPEC have an important role in the initiation of chronic pelvic pain2, a feature of Chronic prostatitis/Chronic pelvic pain syndrome (CP/CPPS)3,4. Infection of the prostate by clinically relevant UPEC can initiate and establish chronic pain through mechanisms that may involve tissue damage and the initiation of mechanisms of autoimmunity5.
A challenge to understanding the pathogenesis of UPEC in the prostate is the relative inaccessibility of the prostate gland to manipulation. We utilized a previously described intraurethral infection method6 to deliver a clinical strain of UPEC into male mice thereby establishing an ascending infection of the prostate. Here, we describe our protocols for standardizing the bacterial inoculum7 as well as the procedure for catheterizing anesthetized male mice for instillation of bacteria.
CP/CPPS is primarily characterized by the presence of tactile allodynia4. Behavior testing was based on the concept of cutaneous hyperalgesia resulting from referred visceral pain8-10. An irritable focus in visceral tissues reduces cutaneous pain thresholds allowing for an exaggerated response to normally non-painful stimuli (allodynia). Application of normal force to the skin result in abnormal responses that tend to increase with the intensity of the underlying visceral pain. We describe methodology in NOD/ShiLtJ mice that utilize von Frey fibers to quantify tactile allodynia over time in response to a single infection with UPEC bacteria.

Infection of the prostate may be a contributing factor in mediating pelvic pain in chronic prostatitis. We describe the procedure for preparation of standardized bacterial inoculum, instillation of bacteria into the urethra of male mice and methodology for measuring tactile allodynia in mice over time.

Uropathogenic Escherichia coli (UPEC) are pathogens that play an important role in urinary tract infections and bacterial prostatitis1. We have recently ...

Cecal Ligation and Puncture-induced Sepsis as a Model To Study Autophagy in Mice

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is provided to induce sepsis of varying severity in mice using the CLP technique. Autophagy is a fundamental tissue response to stress and pathogen invasion. Two current protocols to assess autophagy in vivo in the context of experimental sepsis are also presented here. (I) Transgenic mice expressing green fluorescence protein (GFP)-LC3 fusion protein are subjected to CLP. Localized enhancement of GFP signal (puncta), as assayed either by immunohistochemical or confocal assays, can be used to detect enhanced autophagosome formation and, thus, altered activation of the autophagy pathway. (II) Enhanced autophagic vacuole (autophagosome) formation per unit tissue area (as a marker of autophagy stimulation) can be quantified using electron microscopy. The study of autophagic responses to sepsis is a critical component of understanding the mechanisms by which tissues respond to infection. Research findings in this area may ultimately contribute towards understanding the pathogenesis of sepsis, which represents a major problem in critical care medicine.

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method. Current protocols to assess autophagy in vivo in the context of CLP-induced sepsis are presented here: A protocol for measuring autophagy using (GFP)-LC3 mice, and a protocol for measuring autophagosome formation by electron microscopy.

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is ...

Rapid Identification of Gram Negative Bacteria from Blood Culture Broth Using MALDI-TOF Mass Spectrometry

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional identification requires the sub-culture of signaled blood culture broth with identification available only after colonies on solid agar have matured. MALDI-TOF MS is a reliable, rapid method for identification of the majority of clinically relevant bacteria when applied to colonies on solid media. The application of MALDI-TOF MS directly to blood culture broth is an attractive approach as it has potential to accelerate species identification of bacteria and improve clinical management. However, an important problem to overcome is the pre-analysis removal of interfering resins, proteins and hemoglobin&#160;contained in blood culture specimens which, if not removed, interfere with the MS spectra and can result in insufficient or low discrimination identification scores. In addition it is necessary to concentrate bacteria to develop spectra of sufficient quality. The presented method describes the concentration, purification, and extraction of Gram negative bacteria allowing for the early identification of bacteria from a signaled blood culture broth.

The application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) directly to blood culture broth expedites the identification of bacteria. The presented method is a rapid and reliable method for identification of Gram negative bacteria directly from blood culture broth.

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional ...

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat

Investigation of the interactions between animal host and bacterial pathogen is only meaningful if the infection model employed replicates the principal features of the natural infection. This protocol describes procedures for the establishment and evaluation of systemic infection due to neuropathogenic Escherichia coli K1 in the neonatal rat. Colonization of the gastrointestinal tract leads to dissemination of the pathogen along the gut-lymph-blood-brain course of infection and the model displays strong age dependency. A strain of E. coli O18:K1 with enhanced virulence for the neonatal rat produces exceptionally high rates of colonization, translocation to the blood compartment and invasion of the meninges following transit through the choroid plexus. As in the human host, penetration of the central nervous system is accompanied by local inflammation and an invariably lethal outcome. The model is of proven utility for studies of the mechanism of pathogenesis, for evaluation of therapeutic interventions and for assessment of bacterial virulence.

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat

Here, a procedure is described for the establishment of systemic infection in the neonatal rat with cultures of Escherichia coli K1. This non-invasive procedure permits colonization of the gastrointestinal tract, translocation of the pathogen to the systemic circulation, and invasion of the central nervous system at the choroid plexus.

Investigation of the interactions between animal host and bacterial pathogen is only meaningful if the infection model employed replicates the principal ...

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence factors, which can subvert and manipulate key host functions. The study of host/pathogen interactions is therefore extremely important to understand bacterial infections and develop alternative strategies to counter infectious diseases. This approach however, requires the development of new high-throughput assays for the unbiased, automated identification and characterization of bacterial virulence determinants. Here, we describe a method for the generation of a GFP-tagged mutant library by transposon mutagenesis and the development of high-content screening approaches for the simultaneous identification of multiple transposon-associated phenotypes. Our working model is the intracellular bacterial pathogen Coxiellaburnetii, the etiological agent of the zoonosis Q fever, which is associated with severe outbreaks with a consequent health and economic burden. The obligate intracellular nature of this pathogen has, until recently, severely hampered the identification of bacterial factors involved in host pathogen interactions, making of Coxiella the ideal model for the implementation of high-throughput/high-content approaches.

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Coxiella burnetii is an obligate intracellular Gram-negative bacterium responsible for the zoonotic disease Q fever. Here we describe methods for the generation of Coxiella fluorescent transposon mutants as well as the automated identification and analysis of the resulting internalization, replication and cytotoxic phenotypes.

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence ...

A Controlled Mouse Model for Neonatal Polymicrobial Sepsis

Neonatal sepsis remains a global burden. A preclinical model to screen effective prophylactic or therapeutic interventions is needed. Neonatal mouse polymicrobial sepsis can be induced by injecting cecal slurry intraperitoneally into day of life 7 mice and monitoring them for the following week. Presented here are the detailed steps necessary for the implementation of this neonatal sepsis model. This includes making a homogeneous cecal slurry stock, diluting it to a weight- and litter-adjusted dose, an outline of the monitoring schedule, and a definition of observed health categories used to define humane endpoints. The generation of a homogeneous cecal slurry stock from pooled donors allows for the administration into many litters over time, reducing the variation between donors, and preventing the use of potentially toxic glycerol. The monitoring strategy used allows for the anticipation of survival outcome and the identification of mice that would later progress to death, allowing for an earlier identification of the humane endpoint. Two main behavioral features are used to define the health scores, namely, the ability of the neonatal mice to right themselves when placed on their back and their level of mobility. These criteria could potentially be applied to address humane endpoints in other studies of neonatal disease in mice, as long as a pilot study is performed to confirm accuracy. In conclusion, this approach provides a standardized method to model newborn sepsis in mice, while providing resources to assess animal welfare used to define early humane endpoints for challenged animals.

This protocol provides the necessary steps to establish and evaluate neonatal sepsis in 7-day-old mice.

Neonatal sepsis remains a global burden. A preclinical model to screen effective prophylactic or therapeutic interventions is needed. Neonatal mouse ...

Design of Cecal Ligation and Puncture and Intranasal Infection Dual Model of Sepsis-Induced Immunosuppression

Sepsis, a severe and complicated life-threatening infection, is characterized by an imbalance between pro- and anti-inflammatory responses in multiple organs. With the development of therapies, most patients survive the hyperinflammatory phase but progress to an immunosuppressive phase, which increases the emergence of secondary infections. Therefore, improved understanding of the pathogenesis underlying secondary hospital-acquired infections in the immunosuppressive phase during sepsis is of tremendous importance. Reported here is a model to test infectious outcomes by creating double-hit infections in mice. A standard surgical procedure is used to induce polymicrobial peritonitis by cecal ligation and puncture (CLP) and followed by intranasal infection of Staphylococcus aureus to simulate pneumonia occurring in immune suppression that is frequently seen in septic patients. This dual model can reflect the immunosuppressive state occurring in patients with protracted sepsis and susceptibility to secondary infection from nosocomial pneumonia. Hence, this model provides a simple experimental approach to investigate the pathophysiology of sepsis-induced secondary bacterial pneumonia, which may be used for discovering novel treatments for sepsis and its complications.

This protocol describes techniques to measure infectious outcomes underlying secondary hospital-acquired infections in the immunosuppressive condition, first by establishing cecal ligation/puncture mice then challenging them with intranasal infection to create a clinically relevant model of immunosuppression sepsis.

Sepsis, a severe and complicated life-threatening infection, is characterized by an imbalance between pro- and anti-inflammatory responses in multiple ...