Name: evaluating virulence and pathogenesis of aeromonas infection in a caenorhabditis elegans model
Uploaded: 2018-12-20T13:00:00
Description: Watch this Scientific Journal Video about Evaluating Virulence and Pathogenesis of Aeromonas Infection in a Caenorhabditis elegans Model at JoVE.com

We are grateful for the assistance from the C. elegans core facility in Taiwan and to the Diagnostic Microbiology and Antimicrobial Resistance Laboratory of National Cheng Kung University Hospital for providing the Aeromonas isolates. We also acknowledge the Caenorhabditis Genetics Center (CGC), and the WormBase. We also thank Savana Moore for editing the manuscript.
This study was partially supported by grants from the Ministry of Science and Technology of Taiwan (MOST 105-2628-B-006-017-MY3) and the National Cheng Kung University Hospital (NCKUH-10705001) to P.L. Chen.

1. Preparation of the Culture Medium
NOTE: See Table 1 for solution preparation.
<ol>
	<li>To prepare M9 medium12, dissolve 1.5 g of KH2PO4, 5.66 g of Na2HPO4, and 2.5 g of NaCl in 500 mL of deionized water. Autoclave at 121 &#176;C for 20 min. Wait until cooled to room temperature and then add 0.5 mL of 1 M MgSO4 before first use.</li>
	<li>To prepare nematode growth medium (NGM)12, dissol...

<ol>
	<li>Parker, J. L., Shaw, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aeromonas+spp.+clinical+microbiology+and+disease.">Aeromonas spp. clinical microbiology and disease.</a> Journal of Infection. 62 (2), 109-118 (2011).</li><li>Chao, C. M., Lai, C. C., Tang, H. J., Ko, W. C., Hsueh, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skin+and+soft-tissue+infections+caused+by+Aeromonas+species.">Skin and soft-tissue infections caused by Aeromonas species.</a> European Journal of Clinical Microbiology &amp; Infectious Diseases. 32 (4), 543-547 (2013).</li><li>Chao, C. M., Lai, C. C., Tang, H. J., Ko, W. C., Hsueh, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biliary+tract+infections+caused+by+Aeromonas+species.">Biliary tract infections caused by Aeromonas species.</a> European Journal of Clinical Microbiology &amp; Infectious Diseases. 32 (2), 245-251 (2013).</li><li>Chuang, H. 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=Different+clinical+characteristics+among+Aeromonas+hydrophila,+Aeromonas+veronii+biovar+sobria+and+Aeromonas+caviae+monomicrobial+bacteremia.">Different clinical characteristics among Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae monomicrobial bacteremia.</a> Journal of Korean Medical Science. 26 (11), 1415-1420 (2011).</li><li>Chao, C. M., Lai, C. C., Gau, S. J., Hsueh, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skin+and+soft+tissue+infection+caused+by+Aeromonas+species+in+cancer+patients.">Skin and soft tissue infection caused by Aeromonas species in cancer patients.</a> Journal of Microbiology, Immunology and Infection. 46 (2), 144-146 (2013).</li><li>Chen, P. L., 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=A+Disease+Model+of+Muscle+necrosis+caused+by+Aeromonas+dhakensis+infection+in+Caenorhabditis+elegans.">A Disease Model of Muscle necrosis caused by Aeromonas dhakensis infection in Caenorhabditis elegans.</a> Frontiers in Microbiology. 7, 2058 (2016).</li><li>Chen, P. L., 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=Virulence+diversity+among+bacteremic+Aeromonas+isolates:+ex+vivo,+animal,+and+clinical+evidences.">Virulence diversity among bacteremic Aeromonas isolates: ex vivo, animal, and clinical evidences.</a> PLoS One. 9 (11), 111213 (2014).</li><li>Saraceni, P. R., Romero, A., Figueras, A., Novoa, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+infection+models+in+zebrafish+larvae+(Danio+rerio)+to+study+the+pathogenesis+of+Aeromonas+hydrophila.">Establishment of infection models in zebrafish larvae (Danio rerio) to study the pathogenesis of Aeromonas hydrophila.</a> Frontiers in Microbiology. 7, 1219 (2016).</li><li>Chen, Y. W., Ko, W. C., Chen, C. S., Chen, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RIOK-1+Is+a+Suppressor+of+the+p38+MAPK+Innate+Immune+Pathway+in+Caenorhabditis+elegans.">RIOK-1 Is a Suppressor of the p38 MAPK Innate Immune Pathway in Caenorhabditis elegans.</a> Frontiers in Immunology. 9, 774 (2018).</li><li>Powell, J. R., Ausubel, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+Caenorhabditis+elegans+infection+by+bacterial+and+fungal+pathogens.">Models of Caenorhabditis elegans infection by bacterial and fungal pathogens.</a> Methods in Molecular Biology. 415, 403-427 (2008).</li><li>Chou, T. 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=Enterohaemorrhagic+Escherichia+coli+O157:H7+Shiga-like+toxin+1+is+required+for+full+pathogenicity+and+activation+of+the+p38+mitogen-activated+protein+kinase+pathway+in+Caenorhabditis+elegans.">Enterohaemorrhagic Escherichia coli O157:H7 Shiga-like toxin 1 is required for full pathogenicity and activation of the p38 mitogen-activated protein kinase pathway in Caenorhabditis elegans.</a> Cellular Microbiology. 15 (1), 82-97 (2013).</li><li>Stiernagle, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maintenance+of+C.+elegans.">Maintenance of C. elegans.</a> WormBook. , 1-11 (2006).</li><li>Engelmann, I., Pujol, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Innate+immunity+in+C.+elegans.">Innate immunity in C. elegans.</a> Advances in Experimental Medicine and Biology. 708, 105-121 (2010).</li><li>Feinbaum, R. L., 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-wide+identification+of+Pseudomonas+aeruginosa+virulence-related+genes+using+a+Caenorhabditis+elegans+infection+model.">Genome-wide identification of Pseudomonas aeruginosa virulence-related genes using a Caenorhabditis elegans infection model.</a> PLoS Pathogens. 8 (7), 1002813 (2012).</li></ol>

C. elegans is a bacterivorous nematode that naturally intakes bacteria as food and has developed a complicated innate immunity to bacteria during its evolutionary process. Two of the major organs maintaining and supporting the immunity are the epidermis and intestine9,13. The epidermis and bands of muscle of C. elegans resemble the soft-tissue structures in mammals and humans6. Because of these characteristics, C. ele...

The human pathogen, Aeromonas, has been shown clinically to cause gastroenteritis, wound infections, septicemia, and urinary tract infections1,2. Most associated human diseases have been reported to be associated with four bacterial species: Aeromonas dhakensis, Aeromonas hydrophila, Aeromonas veronii, and Aeromonas caviae 2,3,4,5. Among Aeromonas infectious diseases, soft-tissue infections can cause severe morbidity and mortality in humans. Of note, muscle necrosis is the most severe form of soft tissue infection6. Observation of the survival and muscle necrosis of Caenorhabditis elegans after infection is a convenient method by which to speculate the toxicity of Aeromonas.
Scientists have already developed numerous model organisms to study bacterial infections. In previous studies, mice, zebrafishes, and nematodes were used as animal models to study the pathogenesis and virulence of Aeromonas6,7,8. Every animal model has its&#39; advantages and applications. The model organism, Caenorhabditis elegans, is a bacterivorous nematode which intakes bacteria as foodnaturally.&#160;C. eleganshas developed a complicated innate immune system against bacterial infection over the course of its evolution. Under the stress of bacterial infection,&#160;C. elegans has been proven to be an excellent infection model to study the bacterial pathogenesis of Aeromonas6,7,9 and other pathogens like fungus10 and enterohaemorrhagic Escherichia coli O157:H711. However, there is still no publication that focuses on the methodology in using C. elegans as a model for studying the virulence of Aeromonas.
Here, we introduce three different experiments to study Aeromonas infection using C. elegans as an animal model: assays for survival, liquid toxicity, and muscle necrosis. These methods are a convenient way to evaluate the toxicity among and within Aeromonas species and improve the understanding of the pathogenesis of Aeromonas.

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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Shaker incubator</td>
			<td style="width:119px;">YIH DER</td>
			<td style="width:119px;">LM-570R</td>
			<td style="width:207px;">Bacteria incubation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">K2HPO4</td>
			<td style="width:119px;">J.T.Baker</td>
			<td>MP021519455</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">KH2PO4</td>
			<td style="width:119px;">J.T.Baker</td>
			<td style="width:119px;">3246-05</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Na2HPO4</td>
			<td style="width:119px;">J.T.Baker</td>
			<td style="width:119px;">MP021914405</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">NaCl</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">31434</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MgSO4</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">M7506</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">agar</td>
			<td style="width:119px;">Difco</td>
			<td style="width:119px;">214530</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">CaCl2</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">C1016</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">cholesterol</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">C8503</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ethanol</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">32205</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">KOH</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">P5958</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">6 cm petri plate</td>
			<td style="width:119px;">ALPHA PLUS</td>
			<td style="width:119px;">46</td>
			<td>agar plate preparation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">96-well plate</td>
			<td style="width:119px;">FALCON</td>
			<td style="width:119px;">353072</td>
			<td>liquid assay</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">bacterial peptone</td>
			<td style="width:119px;">Affymetrix/USB</td>
			<td style="width:119px;">AAJ20048P2</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">yeast extract</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">92144</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">citric acid&#8226;H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">C1909</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">tri-potassium citrate&#8226;H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">104956</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">FudR&#160;</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">1271008</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">disodium EDTA</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">E1644</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">FeSO4&#8226;7 H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">215422</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MnCl2&#8226;4 H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">221279</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ZnSO4&#8226;7 H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">204986</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">CuSO4&#8226;5 H2O</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">C8027</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">tryptone</td>
			<td style="width:119px;">SIGMA</td>
			<td style="width:119px;">16922</td>
			<td>Culture medium preparation&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Microscope system</td>
			<td style="width:119px;">Nikon&#160;</td>
			<td style="width:119px;">Eclipase Ti inverted&#160;</td>
			<td>microscope imaging</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Scientific CCD Camera</td>
			<td style="width:119px;">QImaging&#160;</td>
			<td style="width:119px;">Retiga-2000R Fast 1394&#160;</td>
			<td>microscope imaging</td>
		</tr>
	</tbody>
</table>

evaluating virulence and pathogenesis of aeromonas infection in a caenorhabditis elegans model

The human pathogen Aeromonas has been clinically shown to cause gastroenteritis, wound infections, septicemia, and urinary tract infections. Most human diseases have been reported to be associated with four species of bacteria: Aeromonas dhakensis, Aeromonas hydrophila, Aeromonas veronii, and Aeromonas caviae. The model organism Caenorhabditis elegans is a bacterivore that provides an excellent infection model by which to study the bacterial pathogenesis of Aeromonas. Here, we introduce three different experiments to study Aeromonas infection using a C. elegans model, including survival, liquid toxicity, and muscle necrosis assays. The results of the three methods determining the virulence of Aeromonas were consistent. A. dhakensis was shown to be the most toxic among the 4 major Aeromonas species causing clinical infections. These methods are shown to be a convenient way to evaluate the toxicity among and within Aeromonas species and contribute to our understanding of the pathogenesis of Aeromonas infection.

By following the protocols described above, it is easy to differentiate between the toxicities from the four Aeromonas strains. The survival assay of C. elegans is shown in Figure 1. The survival rates of C. elegans infected with Aeromonas species, shown in order from high to low were: A. caviae, A. veronii, A. hydrophila, and A. dhakensis. Although there is diversity in terms of toxicity among and within ...

Watch this Scientific Journal Video about Evaluating Virulence and Pathogenesis of Aeromonas Infection in a Caenorhabditis elegans Model at JoVE.com

Evaluating Virulence and Pathogenesis of Aeromonas Infection in a Caenorhabditis elegans Model

Here, we introduce three different experiments to study Aeromonas infection in C. elegans. Using these convenient methods, it is easy to evaluate the toxicity among and within Aeromonas species.

Evaluating Virulence and Pathogenesis of Aeromonas Infection in a Caenorhabditis elegans Model

The human pathogen Aeromonas has been clinically shown to cause gastroenteritis, wound infections, septicemia, and urinary tract infections. Most human ...

This method can help answer key questions in the host-pathogen interaction field such as the pathogenicity and virulence of bacterial infection. The main advantage of this technique is that we can evaluate the toxicity among and within Aeromonas species and contribute to our understanding of the pathogenesis of Aeromonas infection. To begin wash approximately 2, 000 gravid adult worms with sterile deionized water.Repeat the wash three times keeping the worms at the bottom of the tube. After centrifuging the worms remove the supernatant and keep the worms in 3.5 milliliters of deionized water. Add one milliliter of sodium hypochlorite and 0.5 milliliters of potassium hydroxide to the tube.Then shake the tube for six minutes to lyse the worm bodies. After the eggs are released, add 10 milliliters of deionized water to stop the lysis. Then centrifuge the tube to pull down the eggs and remove as much of the supernatant as possible.Wash the eggs with 15 milliliters of M9 medium at least three times. Transfer the eggs to a 3.5-centimeter dish, and incubate them at 20 degrees Celsius for one night. After this remove 10 microliters of L1 worms and M9 medium from the plate.Count the worms and obtain the concentration of L1 worms in the M9 medium. Using a pipette take 0.5 milliliters of E.coli OP50 LB broth and spread it on an ENGM plate. Then incubate the plate at 37 degrees Celsius for 16 to 18 hours.Cool the ENGM to room temperature. Then seed incubated L1 worms on an ENGM plate with E.coli OP50. Incubate the worms at 20 degrees Celsius until they reach the L4 stage.First, select a single colony of each of the four Aeromonas strains and culture them according to the text protocol. Then measure the OD 600 absorbance of the bacterial broth and adjust it until the absorbance is equal to 2.0. Next spot and spread 30 microliters of bacterial broth from each strain into NGM plates.Randomly select and transfer the previously prepared L4 worms to the NGM plates with the Aeromonas strains. Then incubate the plates at 20 degrees Celsius until the assay is complete. Every day transfer all of the living worms to a new NGM plate with bacteria.Count the numbers of living, dead, and sensor worms every day until the last worm is dead. After culturing Aeromonas strains and measuring their absorbance as previously described, centrifuge the bacterial broth at 3, 500 g's for 15 minutes. Adjust the bacterial broth with S Medium.And add 195 microliters of bacterial broth in the S medium to eight wells of a 96-well plate. Wash the worms off of the ENGM plate with them M9 medium. Then adjust the concentration of the worm solution to five worms per microliter.Add five microliters of the worm solution to each of the wells of the 96-well plate. Incubate the plate on a shaker, and count the number of live worms at 24, 48 and 72 hours. After culturing Aeromonas strains and adjusting the absorbance according to the text protocol spot and spread the bacterial broth on NGM plates.After this, transfer 50 L4 worms to each NGM plate. Every 24 hours transfer the worms to fresh NGM plates. Randomly select 10 worms and transfer them to a 2%agarose gel in M9 medium on a slide.Finally position a coverslip on the gel and capture muscle images with a green fluorescent protein filter on a fluorescent microscope equipped with a camera. In this protocol the toxicities of four Aeromonas strains were assessed. The survival rate of C.elegans infected with Aeromonas species was highest in assays using A.caviae, and lowest in assays using A.dhakensis.In a liquid toxicity assay survival of C.elegans decreased significantly when infected with A.dhakensis or A.hydrophilia. In the muscle necrosis assay degrees of muscle damage varied among the Aeromonas species. A.caviae caused the least muscle damage, while A.dhakensis produced the most muscle damage.The methods described in this video offer a convenient way to differentiate virulence diversity among and within Aeromonas species. Additionally, it is also a reliable model by which to study the interaction between a pathogen and host.

evaluating-virulence-pathogenesis-aeromonas-infection-caenorhabditis

Research

JoVE Journal

Immunology and Infection

In vitro Biofilm Formation in an 8-well Chamber Slide

The chronic nature of many diseases is attributed to the formation of bacterial biofilms which are recalcitrant to traditional antibiotic therapy. Biofilms are community-associated bacteria attached to a surface and encased in a matrix. The role of the extracellular matrix is multifaceted, including facilitating nutrient acquisition, and offers significant protection against environmental stresses (e.g. host immune responses). In an effort to acquire a better understanding as to how the bacteria within a biofilm respond to environmental stresses we have used a protocol wherein we visualize bacterial biofilms which have formed in an 8-well chamber slide. The biofilms were stained with the BacLight Live/Dead stain and examined using a confocal microscope to characterize the relative biofilm size, and structure under varying incubation conditions. Z-stack images were collected via confocal microscopy and analyzed by COMSTAT. This protocol can be used to help elucidate the mechanism and kinetics by which biofilms form, as well as identify components that are important to biofilm structure and stability.

In vitro Biofilm Formation in an 8-well Chamber Slide

This article describes the procedure for the formation and visualization of a bacterial biofilm grown within an 8-well chamber slide

The chronic nature of many diseases is attributed to the formation of bacterial biofilms which are recalcitrant to traditional antibiotic therapy. ...

Using Luciferase to Image Bacterial Infections in Mice

Imaging is a valuable technique that can be used to monitor biological processes. In particular, the presence of cancer cells, stem cells, specific immune cell types, viral pathogens, parasites and bacteria can be followed in real-time within living animals 1-2. Application of bioluminescence imaging to the study of pathogens has advantages as compared to conventional strategies for analysis of infections in animal models3-4. Infections can be visualized within individual animals over time, without requiring euthanasia to determine the location and quantity of the pathogen. Optical imaging allows comprehensive examination of all tissues and organs, rather than sampling of sites previously known to be infected. In addition, the accuracy of inoculation into specific tissues can be directly determined prior to carrying forward animals that were unsuccessfully inoculated throughout the entire experiment. Variability between animals can be controlled for, since imaging allows each animal to be followed individually. Imaging has the potential to greatly reduce animal numbers needed because of the ability to obtain data from numerous time points without having to sample tissues to determine pathogen load3-4.
This protocol describes methods to visualize infections in live animals using bioluminescence imaging for recombinant strains of bacteria expressing luciferase. The click beetle (CBRLuc) and firefly luciferases (FFluc) utilize luciferin as a substrate5-6. The light produced by both CBRluc and FFluc has a broad wavelength from 500 nm to 700 nm, making these luciferases excellent reporters for the optical imaging in living animal models7-9. This is primarily because wavelengths of light greater than 600 nm are required to avoid absorption by hemoglobin and, thus, travel through mammalian tissue efficiently. Luciferase is genetically introduced into the bacteria to produce light signal10. Mice are pulmonary inoculated with bioluminescent bacteria intratracheally to allow monitoring of infections in real time. After luciferin injection, images are acquired using the IVIS Imaging System. During imaging, mice are anesthetized with isoflurane using an XGI-8 Gas Anethesia System. Images can be analyzed to localize and quantify the signal source, which represents the bacterial infection site(s) and number, respectively. After imaging, CFU determination is carried out on homogenized tissue to confirm the presence of bacteria. Several doses of bacteria are used to correlate bacterial numbers with luminescence. Imaging can be applied to study of pathogenesis and evaluation of the efficacy of antibacterial compounds and vaccines.

Methods for bioluminescence imaging of bacterial infections in living animals are decribed. Pathogens are modified to express luciferase allowing optical whole body imaging of infections in live animals. Animal models can be infected with luciferase expressing pathogens and the resulting course of disease visualized in real-time by bioluminescence imaging.

Imaging is a valuable technique that can be used to monitor biological processes.  In particular, the presence of cancer cells, stem cells, specific ...

The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis

The study of bacterial virulence often requires a suitable animal model. Mammalian models of infection are costly and may raise ethical issues. The use of insects as infection models provides a valuable alternative. Compared to other non-vertebrate model hosts such as nematodes, insects have a relatively advanced system of antimicrobial defenses and are thus more likely to produce information relevant to the mammalian infection process. Like mammals, insects possess a complex innate immune system1. Cells in the hemolymph are capable of phagocytosing or encapsulating microbial invaders, and humoral responses include the inducible production of lysozyme and small antibacterial peptides2,3. In addition, analogies are found between the epithelial cells of insect larval midguts and intestinal cells of mammalian digestive systems. Finally, several basic components essential for the bacterial infection process such as cell adhesion, resistance to antimicrobial peptides, tissue degradation and adaptation to oxidative stress are likely to be important in both insects and mammals1. Thus, insects are polyvalent tools for the identification and characterization of microbial virulence factors involved in mammalian infections.
Larvae of the greater wax moth Galleria mellonella have been shown to provide a useful insight into the pathogenesis of a wide range of microbial infections including mammalian fungal (Fusarium oxysporum, Aspergillus fumigatus, Candida albicans) and bacterial pathogens, such as Staphylococcus aureus, Proteus vulgaris, Serratia marcescens Pseudomonas aeruginosa, Listeria monocytogenes or Enterococcus faecalis4-7. Regardless of the bacterial species, results obtained with Galleria larvae infected by direct injection through the cuticle consistently correlate with those of similar mammalian studies: bacterial strains that are attenuated in mammalian models demonstrate lower virulence in Galleria, and strains causing severe human infections are also highly virulent in the Galleria model8-11. Oral infection of Galleria is much less used and additional compounds, like specific toxins, are needed to reach mortality.
G. mellonella larvae present several technical advantages: they are relatively large (last instar larvae before pupation are about 2 cm long and weight 250 mg), thus enabling the injection of defined doses of bacteria; they can be reared at various temperatures (20 &deg;C to 30 &deg;C) and infection studies can be conducted between 15 &deg;C to above 37 &deg;C12,13, allowing experiments that mimic a mammalian environment. In addition, insect rearing is easy and relatively cheap. Infection of the larvae allows monitoring bacterial virulence by several means, including calculation of LD5014, measurement of bacterial survival15,16 and examination of the infection process17. Here, we describe the rearing of the insects, covering all life stages of G. mellonella. We provide a detailed protocol of infection by two routes of inoculation: oral and intra haemocoelic. The bacterial model used in this protocol is Bacillus cereus, a Gram positive pathogen implicated in gastrointestinal as well as in other severe local or systemic opportunistic infections18,19.

The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis

Oral and intra haemocolic infection of larvae of the greater wax moth Galleria mellonella is described. This insect can be used to study virulence factors of entomopathogenic as well as mammalian opportunistic bacteria. Rearing of the insects, methods of infection and examples of in vivo analysis are described.

The study of bacterial virulence often requires a suitable animal model. Mammalian models of infection are costly and may raise ethical issues. The use of ...

Monitoring Changes in Membrane Polarity, Membrane Integrity, and Intracellular Ion Concentrations in Streptococcus pneumoniae Using Fluorescent Dyes

Membrane depolarization and ion fluxes are events that have been studied extensively in biological systems due to their ability to profoundly impact cellular functions, including energetics and signal transductions. While both fluorescent and electrophysiological methods, including electrode usage and patch-clamping, have been well developed for measuring these events in eukaryotic cells, methodology for measuring similar events in microorganisms have proven more challenging to develop given their small size in combination with the more complex outer surface of bacteria shielding the membrane. During our studies of death-initiation in Streptococcus pneumoniae (pneumococcus), we wanted to elucidate the role of membrane events, including changes in polarity, integrity, and intracellular ion concentrations. Searching the literature, we found that very few studies exist. Other investigators had monitored radioisotope uptake or equilibrium to measure ion fluxes and membrane potential and a limited number of studies, mostly in Gram-negative organisms, had seen some success using carbocyanine or oxonol fluorescent dyes to measure membrane potential, or loading bacteria with cell-permeant acetoxymethyl (AM) ester versions of ion-sensitive fluorescent indicator dyes. We therefore established and optimized protocols for measuring membrane potential, rupture, and ion-transport in the Gram-positive organism S. pneumoniae. We developed protocols using the bis-oxonol dye DiBAC4(3) and the cell-impermeant dye propidium iodide to measure membrane depolarization and rupture, respectively, as well as methods to optimally load the pneumococci with the AM esters of the ratiometric dyes Fura-2, PBFI, and BCECF to detect changes in intracellular concentrations of Ca2+, K+, and H+, respectively, using a fluorescence-detection plate reader. These protocols are the first of their kind for the pneumococcus and the majority of these dyes have not been used in any other bacterial species. Though our protocols have been optimized for S. pneumoniae, we believe these approaches should form an excellent starting-point for similar studies in other bacterial species.

Monitoring Changes in Membrane Polarity, Membrane Integrity, and Intracellular Ion Concentrations in Streptococcus pneumoniae Using Fluorescent Dyes

Unlike that seen for eukaryotes, there is a paucity of studies that detail membrane depolarization and ion concentration changes in bacteria, primarily as their small size makes conventional methods of measurement difficult. Here, we detail protocols for monitoring such events in the significant Gram-positive pathogen Streptococcus pneumoniae utilizing fluorescence techniques.

Membrane depolarization and ion fluxes are events that have been studied extensively in biological systems due to their ability to profoundly impact ...

Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria

Pneumonia is one of the major health care problems in developing and industrialized countries and is associated with considerable morbidity and mortality. Despite advances in knowledge of this illness, the availability of intensive care units (ICU), and the use of potent antimicrobial agents and effective vaccines, the mortality rates remain high1. Streptococcus pneumoniae is the leading pathogen of community-acquired pneumonia (CAP) and one of the most common causes of bacteremia in humans. This pathogen is equipped with an armamentarium of surface-exposed adhesins and virulence factors contributing to pneumonia and invasive pneumococcal disease (IPD). The assessment of the in vivo role of bacterial fitness or virulence factors is of utmost importance to unravel S. pneumoniae pathogenicity mechanisms. Murine models of pneumonia, bacteremia, and meningitis are being used to determine the impact of pneumococcal factors at different stages of the infection. Here we describe a protocol to monitor in real-time pneumococcal dissemination in mice after intranasal or intraperitoneal infections with bioluminescent bacteria. The results show the multiplication and dissemination of pneumococci in the lower respiratory tract and blood, which can be visualized and evaluated using an imaging system and the accompanying analysis software.

Streptococcus pneumoniae is the leading pathogen causing severe community-acquired pneumonia and responsible for over 2&#160;million deaths worldwide. The impact of bacterial factors implicated in fitness or virulence can be monitored in real-time in an acute mouse pneumonia or bacteremia model using bioluminescent bacteria.

Pneumonia is one of the major health care problems in developing and industrialized countries and is associated with considerable morbidity and mortality. ...

A Protocol to Infect Caenorhabditis elegans with Salmonella typhimurium

In the last decade, C. elegans has emerged as an invertebrate organism to study interactions between hosts and pathogens, including the host defense against gram-negative bacterium Salmonella typhimurium. Salmonella establishes persistent infection in the intestine of C. elegans and results in early death of infected animals. A number of immunity mechanisms have been identified in C. elegans to defend against Salmonella infections. Autophagy, an evolutionarily conserved lysosomal degradation pathway, has been shown to limit the Salmonella replication in C. elegans and in mammals. Here, a protocol is described to infect C. elegans with Salmonella typhimurium, in which the worms are exposed to Salmonella for a limited time, similar to Salmonella infection in humans. Salmonella infection significantly shortens the lifespan of C. elegans. Using the essential autophagy gene bec-1 as an example, we combined this infection method with C. elegans RNAi feeding approach and showed this protocol can be used to examine the function of C. elegans host genes in defense against Salmonella infection. Since C. elegans whole genome RNAi libraries are available, this protocol makes it possible to comprehensively screen for C. elegans genes that protect against Salmonella and other intestinal pathogens using genome-wide RNAi libraries.

A Protocol to Infect Caenorhabditis elegans with Salmonella typhimurium

C. elegans has emerged as a new genetic model to study host-pathogen interactions. Here we describe a protocol to infect C. elegans with Salmonella typhimurium coupled with the double-strand RNAi interference technique to examine the role of host genes in defense against Salmonella infection.

In the last decade, C. elegans has emerged as an invertebrate organism to study interactions between hosts and pathogens, including the host defense ...

The Madagascar Hissing Cockroach as an Alternative Non-mammalian Animal Model to Investigate Virulence, Pathogenesis, and Drug Efficacy

Many aspects of innate immunity are conserved between mammals and insects. An insect, the Madagascar hissing cockroach from the genus Gromphadorhina, can be utilized as an alternative animal model for the study of virulence, host-pathogen interaction, innate immune response, and drug efficacy. Details for the rearing, care and breeding of the hissing cockroach are provided. We also illustrate how it can be infected with bacteria such as the intracellular pathogens Burkholderia mallei, B. pseudomallei, and B. thailandensis. Use of the hissing cockroach is inexpensive and overcomes regulatory issues dealing with the use of mammals in research. In addition, results found using the hissing cockroach model are reproducible and similar to those obtained using mammalian models. Thus, the Madagascar hissing cockroach represents an attractive surrogate host that should be explored when conducting animal studies.

We present a protocol to utilize the Madagascar hissing cockroach as an alternative non-mammalian animal model to conduct bacterial virulence, pathogenesis, drug toxicity, drug efficacy, and innate immune response studies.

Many aspects of innate immunity are conserved between mammals and insects. An insect, the Madagascar hissing cockroach from the genus Gromphadorhina, can ...

Establishment of the Dual Humanized TK-NOG Mouse Model for HIV-associated Liver Pathogenesis

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of their morbidity. The liver immunopathology caused by HIV-1 remains elusive. Small xenograft animal models with human hepatocytes and human immune system can recapitulate the human biology of the disease&#39;s pathogenesis. Herein, a protocol is described to establish a dual humanized mouse model through human hepatocytes and CD34+ hematopoietic stem/progenitor cells (HSPCs) transplantation, to study liver immunopathology as observed in HIV-infected patients. To achieve dual reconstitution, male TK-NOG (NOD.Cg-Prkdcscid Il2rgtm1Sug Tg(Alb-TK)7-2/ShiJic) mice are intraperitoneally injected with ganciclovir (GCV) doses to eliminate mouse transgenic liver cells, and with treosulfan for nonmyeloablative conditioning, both of which facilitate human hepatocyte (HEP) engraftment and human immune system (HIS) development. Human albumin (ALB) levels are evaluated for liver engraftment, and the presence of human immune cells in blood detected by flow cytometry confirms the establishment of human immune system. The model developed using the protocol described here resembles multiple components of liver damage from HIV-1 infection. Its establishment could prove to be essential for studies of hepatitis virus co-infection and for the evaluation of antiviral and antiretroviral drugs.

This protocol provides a reliable method to establish humanized mice with both human immune system and liver cells. Dual reconstituted immunodeficient mice achieved via intrasplenic injection of human hepatocytes and CD34+ hematopoietic stem cells are susceptible to human immunodeficiency virus-1 infection and recapitulate liver damage as observed in HIV-infected patients.

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of ...

Stem Cell-Derived Viral Ag-Specific T Lymphocytes Suppress HBV Replication in Mice

Hepatitis B virus (HBV) infection is a global health issue. With over 350 million people affected worldwide, HBV infection remains the leading cause of liver cancer. This is a major concern, especially in developing countries. Failure of the immune system to mount an effective response against HBV leads to chronic infection. Although HBV vaccine is present and novel antiviral medicines are being created, eradication of virus-reservoir cells remains a major health topic. Described here is a method for the generation of viral antigen (Ag) -specific CD8+ cytotoxic T lymphocytes (CTLs) derived from induced pluripotent stem cells (iPSCs) (i.e., iPSC-CTLs), which have the ability to suppress HBV replication. HBV replication is efficiently induced in mice through hydrodynamic injection of an HBV expression plasmid, pAAV/HBV1.2, into the liver. Then, HBV surface Ag-specific mouse iPSC-CTLs are adoptively transferred, which greatly suppresses HBV replication in the liver and blood as well as prevents HBV surface Ag expression in hepatocytes. This method demonstrates HBV replication in mice after hydrodynamic injection and that stem cell-derived viral Ag-specific CTLs can suppress HBV replication. This protocol provides a useful method for HBV immunotherapy.

Presented here is a protocol for the effective suppression of hepatitis B virus (HBV) replication in mice by utilizing adoptive cell transfer (ACT) of stem cell-derived viral antigen (Ag)-specific T lymphocytes. This procedure may be adapted for potential ACT-based immunotherapy of HBV infection.

Hepatitis B virus (HBV) infection is a global health issue. With over 350 million people affected worldwide, HBV infection remains the leading cause of ...

Generation of In-Frame Gene Deletion Mutants in Pseudomonas aeruginosa and Testing for Virulence Attenuation in a Simple Mouse Model of Infection

Microorganisms are genetically versatile and diverse and have become a major source of many commercial products and biopharmaceuticals. Though some of these products are naturally produced by the organisms, other products require genetic engineering of the organism to increase the yields of production. Avirulent strains of Escherichia coli have traditionally been the preferred bacterial species for producing biopharmaceuticals; however, some products are difficult for E. coli to produce. Thus, avirulent strains of other bacterial species could provide useful alternatives for production of some commercial products. Pseudomonas aeruginosa is a common and well-studied Gram-negative bacterium that could provide a suitable alternative to E. coli. However, P. aeruginosa is an opportunistic human pathogen. Here, we detail a procedure that can be used to generate nonpathogenic strains of P. aeruginosa through sequential genomic deletions using the pEX100T-NotI plasmid. The main advantage of this method is to produce a marker-free strain. This method may be used to generate highly attenuated P. aeruginosa strains for the production of commercial products, or to design strains for other specific uses. We also describe a simple and reproducible mouse model of bacterial systemic infection via intraperitoneal injection of validated test strains to test the attenuation of the genetically engineered strain in comparison to the FDA-approved BL21 strain of E. coli.

Generation of In-Frame Gene Deletion Mutants in Pseudomonas aeruginosa and Testing for Virulence Attenuation in a Simple Mouse Model of Infection

Here, we describe a simple and reproducible protocol of mouse model of infection to evaluate the attenuation of the genetically modified strains of Pseudomonas aeruginosa in comparison to the United States Food and Drug Administration (FDA)-approved Escherichia coli for commercial applications.

Microorganisms are genetically versatile and diverse and have become a major source of many commercial products and biopharmaceuticals. Though some of ...