Thanks to Melody Neely, Jon Allen, Basel Abuaita, and Donna Runft for their efforts in helping to develop the zebrafish model. The research reported here was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health under award numbers R21AI095520 and R01AI127390 (to Jeffrey H. Withey). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Wayne State University. This method was first described in Runft et al.12
1. Determination of Intestinal Colonization Levels
NOTE: Intestinal colonization is the most useful metric in the zebrafish model as it can be used to compare the relative fitness of various V. cholerae strains or the effects of mutations or gene k...

<ol>
	<li>Harris, J. B., LaRocque, R. C., Qadri, F., Ryan, E. T., Calderwood, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cholera.">Cholera.</a> The Lancet. 379 (9835), 2466-2476 (2012).</li><li>Dutta, 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=Vibrio+cholerae+non-O1,+non-O139+serogroups+and+cholera-like+diarrhea,+Kolkata,+India.">Vibrio cholerae non-O1, non-O139 serogroups and cholera-like diarrhea, Kolkata, India.</a> Emerging Infectious Diseases. 19 (3), 464-467 (2013).</li><li>Huq, 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=Ecological+relationships+between+Vibrio+cholerae+and+planktonic+crustacean+copepods.">Ecological relationships between Vibrio cholerae and planktonic crustacean copepods.</a> Applied and Environmental Microbiology. 45 (1), 275-283 (1983).</li><li>Halpern, M., Landsberg, O., Raats, D., Rosenberg, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culturable+and+VBNC+Vibrio+cholerae:+interactions+with+chironomid+egg+masses+and+their+bacterial+population.">Culturable and VBNC Vibrio cholerae: interactions with chironomid egg masses and their bacterial population.</a> Microbial Ecology. 53 (2), 285-293 (2007).</li><li>Broza, M., Halpern, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogen+reservoirs.+Chironomid+egg+masses+and+Vibrio+cholerae.">Pathogen reservoirs. Chironomid egg masses and Vibrio cholerae.</a> Nature. 412 (6842), 40 (2001).</li><li>Halpern, M., Izhaki, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fish+as+hosts+of+Vibrio+cholerae.">Fish as hosts of Vibrio cholerae.</a> Frontiers in Microbiology. 8 (282), (2017).</li><li>Senderovich, Y., Izhaki, I., Halpern, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fish+as+reservoirs+and+vectors+of+Vibrio+cholerae.">Fish as reservoirs and vectors of Vibrio cholerae.</a> PLoS ONE. 5 (1), e8607 (2010).</li><li>Traore, O., 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=Occurrence+of+Vibrio+cholerae+in+fish+and+water+from+a+reservoir+and+a+neighboring+channel+in+Ouagadougou,+Burkina+Faso.">Occurrence of Vibrio cholerae in fish and water from a reservoir and a neighboring channel in Ouagadougou, Burkina Faso.</a> The Journal of Infection in Developing Countries. 8 (10), 1334-1338 (2014).</li><li>Booth, L. V., Lang, D. A., Athersuch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+Vibrio+cholerae+non-01+from+a+Somerset+farmworker+and+his+tropical+fish+tank.">Isolation of Vibrio cholerae non-01 from a Somerset farmworker and his tropical fish tank.</a> Journal of Infection. 20 (1), 55-57 (1990).</li><li>Torres-Vitela, M. 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=Incidence+of+Vibrio+cholerae+in+fresh+fish+and+ceviche+in+Guadalajara,+Mexico.">Incidence of Vibrio cholerae in fresh fish and ceviche in Guadalajara, Mexico.</a> Journal of Food Protection. 60 (3), 237-241 (1997).</li><li>Rowe, H. M., Withey, J. H., Neely, M. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+as+a+model+for+zoonotic+aquatic+pathogens.">Zebrafish as a model for zoonotic aquatic pathogens.</a> Developmental &amp; Comparative Immunology. 46 (1), 96-107 (2014).</li><li>Runft, D. 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=Zebrafish+as+a+natural+host+model+for+Vibrio+cholerae+colonization+and+transmission.">Zebrafish as a natural host model for Vibrio cholerae colonization and transmission.</a> Applied and Environmental Microbiology. 80 (5), 1710-1717 (2014).</li><li>Mitchell, K. C., Breen, P., Britton, S., Neely, M. N., Withey, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+Vibrio+cholerae+enterotoxicity+in+a+zebrafish+infection+model.">Quantifying Vibrio cholerae enterotoxicity in a zebrafish infection model.</a> Applied and Environmental Microbiology. , (2017).</li><li>Klose, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+suckling+mouse+model+of+cholera.">The suckling mouse model of cholera.</a> Trends in Microbiology. 8 (4), 189-191 (2000).</li><li>Formal, S. B., Kundel, D., Schneider, H., Kunevn, H., Sprinz, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+with+Vibrio+cholerae+in+the+ligated+loop+of+the+rabbit+intestine.">Studies with Vibrio cholerae in the ligated loop of the rabbit intestine.</a> British Journal of Experimental Pathology. 42, 504-510 (1961).</li><li>Williams, E. M., Dohadwalla, A. N., Dutta, N. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diarrhea+and+accumulation+of+intestinal+fluid+in+infant+rabbits+infected+with+Vibrio+cholerae+in+an+isolated+jejunal+segment.">Diarrhea and accumulation of intestinal fluid in infant rabbits infected with Vibrio cholerae in an isolated jejunal segment.</a> The Journal of Infectious Diseases. 120 (6), 645-651 (1969).</li><li>Spira, W. M., Sack, R. B., Froehlich, 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=Simple+adult+rabbit+model+for+Vibrio+cholerae+and+enterotoxigenic+Escherichia+coli+diarrhea.">Simple adult rabbit model for Vibrio cholerae and enterotoxigenic Escherichia coli diarrhea.</a> Infection and Immunity. 32 (2), 739-747 (1981).</li><li>Ritchie, J. M., Rui, H., Bronson, R. T., Waldor, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Back+to+the+future:+studying+cholera+pathogenesis+using+infant+rabbits.">Back to the future: studying cholera pathogenesis using infant rabbits.</a> mBio. 1 (1), (2010).</li><li>Kilcoyne, M., Gerlach, J. Q., Farrell, M. P., Bhavanandan, V. P., Joshi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Periodic+acid-Schiff's+reagent+assay+for+carbohydrates+in+a+microtiter+plate+format.">Periodic acid-Schiff's reagent assay for carbohydrates in a microtiter plate format.</a> Analytical Biochemistry. 416 (1), 18-26 (2011).</li><li>Balaji, V., Sridharan, G., Jesudason, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytotoxicity+of+non+O1,+non+O139+Vibrios+isolated+from+fresh+water+bodies+in+Vellore,+south+India.">Cytotoxicity of non O1, non O139 Vibrios isolated from fresh water bodies in Vellore, south India.</a> Indian Journal of Medical Research. 110, 155-159 (1999).</li><li>Hasan, N. 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=Nontoxigenic+Vibrio+cholerae+non-O1/O139+isolate+from+a+case+of+human+gastroenteritis+in+the+U.S.+Gulf+Coast.">Nontoxigenic Vibrio cholerae non-O1/O139 isolate from a case of human gastroenteritis in the U.S. Gulf Coast.</a> Journal of Clinical Microbiology. 53 (1), 9-14 (2015).</li></ol>

The authors have nothing to disclose.

The zebrafish is a relatively new model for studying V. cholerae but holds much promise for the future discovery of previously unknown aspects of V. cholerae biology and pathogenesis11,12,13. The adult zebrafish model has the advantages of being both a natural V. cholerae host that contains intact, mature intestinal microbiota and an environmental model. Disadvantages of the model are that the two majo...

Vibrio cholerae is an aquatic, Gram-negative bacterium that causes the human disease cholera as well as sporadic diarrhea1,2. V. cholerae is found in the environment in many areas of the globe, often associated with other aquatic organisms. These associating organisms include plankton, insect egg masses, shellfish, and vertebrate fish species3,4,5,6,7. Several studies have isolated V. cholerae from the intestinal tracts of fish in different geographical areas7,8,9,10. The presence of V. cholerae in fish indicates that fish may act as an environmental reservoir. Fish could also be implicated in transmitting the disease to humans and in the geographic spreading of V. cholerae strains6.
To better understand how V. cholerae interacts with fish, Danio rerio, better known as zebrafish, was developed as a model system for studying V. cholerae11. Zebrafish are native to southern Asia, including the Bay of Bengal region, which is thought to be the earliest reservoir of V. cholerae. Prior to the first cholera pandemic beginning in 1817, cholera had not been reported outside of what is now India and Bangladesh. Therefore, zebrafish and V. cholerae almost certainly associated with each other over evolutionary time scales, suggesting that zebrafish are a V. cholerae host in the natural environment12.
The zebrafish model for V. cholerae is simple to execute and can be used to study the entire pathogenic V. cholerae life cycle. Fish are exposed to V. cholerae by bathing in water that has been inoculated with a known number of V. cholerae. Within a few hours, intestinal colonization takes place, followed by the production of diarrhea. Diarrhea consists of mucin, proteins, excreted bacteria, and other intestinal contents. The degree of diarrhea can be quantified using a few simple measurements13. V. cholerae that has been excreted by infected fish can then go on to infect na&#239;ve fish, completing the infectious cycle. Therefore, the zebrafish model recapitulates the V. cholerae human disease process12,14.
The most frequently used V. cholerae animal models have historically been mice and rabbits14,15,16,17,18. These models have been instrumental in adding to our knowledge of V. cholerae pathogenesis. However, because mice and rabbits are not natural V. cholerae hosts, there are limitations to what aspects of the V. cholerae life cycle can be studied. The V. cholerae colonization of mice and rabbits typically requires the absence of intestinal microbiota or a pretreatment with antibiotics to damage the intestinal microbiota. Both models require either gavage to introduce the bacteria to the digestive tract or surgical manipulation to directly inject the bacteria into the intestines. Zebrafish have an advantage in that adult fish with an intact intestinal microbiota are readily colonized and the infectious process happens naturally, without any manipulation required.
The present work demonstrates the utilization of zebrafish as a model in V. cholerae infection. The infection, dissection, enumeration of colonizing V. cholerae, and the quantification of diarrhea caused by V. cholerae will be described12,13. This model is likely to be useful to scientists interested both in the V. cholerae disease process and in the V. cholerae environmental lifestyle.

<table>
	<tbody>
		<tr>
			<td>Instrument</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Shaker incubator</td>
			<td>New Brunswick Scientific, Edison, NJ</td>
			<td>Excella E25</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>NUAIRE, Plymouth, MN</td>
			<td>Auto Flow</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrophotometer</td>
			<td>Thermo, Waltham, MA</td>
			<td>Geaesys 6</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex homogenizer</td>
			<td>Minibeadbeater24</td>
			<td>112011</td>
			<td></td>
		</tr>
		<tr>
			<td>Weighing Machine</td>
			<td>Ohaus, Columbia, MD</td>
			<td>Adventurer Pro</td>
			<td></td>
		</tr>
		<tr>
			<td>Heat Stirer</td>
			<td>Corning, Corning, NY</td>
			<td>PC-420D</td>
			<td></td>
		</tr>
		<tr>
			<td>Burner</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>automated colony counter</td>
			<td>REVSCI</td>
			<td>120417B</td>
			<td></td>
		</tr>
		<tr>
			<td>Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>400 ml glass beakers</td>
			<td>Pyrex</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>perforated lids</td>
			<td>Microtip holder with holes from tip box</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>disposable plastic spoons</td>
			<td>Office Depot, Boca Raton, FL</td>
			<td>D15-25-7008</td>
			<td></td>
		</tr>
		<tr>
			<td>Fish Tank System</td>
			<td>Aquaneering, San Diego, CA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>RO Water Purifier</td>
			<td>Aqua FX</td>
			<td>TK001</td>
			<td></td>
		</tr>
		<tr>
			<td>Fish net</td>
			<td>Marina</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>fish food</td>
			<td>Tetra fin</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Brine Shrimp</td>
			<td>Red jungle brand</td>
			<td>O.S.I. pro 80</td>
			<td></td>
		</tr>
		<tr>
			<td>Styrofoam board</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pins</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpels</td>
			<td>Fine Scientific tools, Foster City, CA</td>
			<td>10000-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fine Scientific tools, Foster City, CA</td>
			<td>11223-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas scissors</td>
			<td>Fine Scientific tools, Foster City, CA</td>
			<td>15000-11</td>
			<td></td>
		</tr>
		<tr>
			<td>2 ml screw cap tubes</td>
			<td>Fisher Scientific, Hampton, NH</td>
			<td>02-681-375</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mm glass beads</td>
			<td>Bio Spec</td>
			<td>11079110</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass beads for spreading</td>
			<td>Sigma, St. Louis, MO</td>
			<td>18406-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri plate</td>
			<td>Fisher Brand, Hampton, NH</td>
			<td>FB0875713</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml centrifuge tube</td>
			<td>Midsci, Valley Park, MO</td>
			<td>AVSS1700</td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml centrifuge tube</td>
			<td>Corning Falcon, Corning, NY</td>
			<td>352098</td>
			<td></td>
		</tr>
		<tr>
			<td>Test tubes</td>
			<td>Pyrex</td>
			<td>9820</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Pipette</td>
			<td>Fisher Brand, Hampton, NH</td>
			<td>13675K</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro pipettes</td>
			<td>Sartorius Biohit, G&#246;ttingen, Germany</td>
			<td>m1000/m200/m20</td>
			<td></td>
		</tr>
		<tr>
			<td>Tips</td>
			<td>Genesee Scientific, San Diego, CA</td>
			<td>24-150RS/24-412</td>
			<td></td>
		</tr>
		<tr>
			<td>Chemicals</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Instant Ocean salts</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>phosphate buffered saline</td>
			<td>VWR Life Science, Radnor, PA</td>
			<td>K813-500ml</td>
			<td></td>
		</tr>
		<tr>
			<td>Tricaine (ethyl 3-aminobenzoate methanesulfonate salt</td>
			<td>Sigma, St. Louis, MO</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr>
			<td>5-Bromo-4-chloro-3-indolyl-&#946;-D-galactopyranoside</td>
			<td>Sigma, St. Louis, MO</td>
			<td>10651745001</td>
			<td></td>
		</tr>
		<tr>
			<td>Schiff&#8217;s reagent</td>
			<td>Sigma, St. Louis, MO</td>
			<td>84655-250 mL</td>
			<td></td>
		</tr>
		<tr>
			<td>periodic acid</td>
			<td>Fisher Scientific, Hampton, NH</td>
			<td>10450-60-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Mucin from porcine stomach</td>
			<td>Sigma, St. Louis, MO</td>
			<td>M2378-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Fisher Scientific, Hampton, NH</td>
			<td>9046-46-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce 660nm Protein Assay Reagent</td>
			<td>Thermo, Waltham, MA</td>
			<td>22660</td>
			<td></td>
		</tr>
		<tr>
			<td>LB medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Trypton</td>
			<td>BD Biosciences, San Jose, CA</td>
			<td>211705</td>
			<td></td>
		</tr>
		<tr>
			<td>Teast Extract</td>
			<td>BD Biosciences, San Jose, CA</td>
			<td>212750</td>
			<td></td>
		</tr>
		<tr>
			<td>NACL</td>
			<td>Fisher Scientific, Hampton, NH</td>
			<td>BP358-212</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>BD Biosciences, San Jose, CA</td>
			<td>214010</td>
			<td></td>
		</tr>
		<tr>
			<td>TCBS Agar</td>
			<td>BD Biosciences, San Jose, CA</td>
			<td>265020</td>
			<td></td>
		</tr>
		<tr>
			<td>DCLS Agar</td>
			<td>Sigma, St. Louis, MO</td>
			<td>70135-500gm</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microsoft office</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Prism 5</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

quantifying vibrio cholerae colonization and diarrhea in the adult zebrafish model

Vibrio cholerae is best known as the infectious agent that causes the human disease cholera. Outside the human host, V. cholerae primarily exists in the aquatic environment, where it interacts with a variety of higher aquatic species. Vertebrate fish are known to be an environmental host and are a potential V. cholerae reservoir in nature. Both V. cholerae and the teleost fish species Danio rerio, commonly known as zebrafish, originate from the Indian subcontinent, suggesting a long-standing interaction in aquatic environments. Zebrafish are an ideal model organism for studying many aspects of biology, including infectious diseases. Zebrafish can be easily and rapidly colonized by V. cholerae after exposure in water. Intestinal colonization by V. cholerae leads to the production of diarrhea and the excretion of replicated V. cholerae. These excreted bacteria can then go on to colonize new fish hosts. Here, we demonstrate how to assess V. cholerae-intestinal colonization in zebrafish and how to quantify V. cholerae-induced zebrafish diarrhea. The colonization model should be useful to researchers who are studying whether genes of interest may be important for host colonization and/or for environmental survival. The quantification of zebrafish diarrhea should be useful to researchers studying any intestinal pathogen who are interested in exploring zebrafish as a model system.

V. cholerae colonization of zebrafish intestinal tracts
To provide an example of the typical colonization levels we observe, we inoculated 5 x 106 CFU of the pandemic EL Tor V. cholerae strain N16961 in 200 mL of water in a beaker containing several zebrafish. After 6 h of infection, the fish were washed in fresh water and transferred into a beaker of 200 mL of autoclaved infection water as described in...

Watch this Scientific Journal Video about Quantifying Vibrio cholerae Colonization and Diarrhea in the Adult Zebrafish Model at JoVE.com

Quantifying Vibrio cholerae Colonization and Diarrhea in the Adult Zebrafish Model

Zebrafish are a natural Vibrio cholerae host and can be used to recapitulate and study the entire infectious cycle from colonization to transmission. Here, we demonstrate how to assess V. cholerae colonization levels and quantify diarrhea in zebrafish.

Quantifying Vibrio cholerae Colonization and Diarrhea in the Adult Zebrafish Model

Vibrio cholerae is best known as the infectious agent that causes the human disease cholera. Outside the human host, V. cholerae primarily exists in the ...

This method can help answer key questions in the vibrio cholerae field, such as how the vibrio cholerae colonizes in the Quiet Coast and competes with the intestinal microbiota to establish a niche. The main advantage of this technique is that fish are a natural vibrio cholerae host so we can study the complete vibrio cholerae life cycle. Demonstrating the procedure will be Dhrubajyoti Nag, a postdoc from my laboratory and Paul Breen, a Ph.D.student from my laboratory.After preparing the V.cholerae cultures, inoculate the zebrafish by immersion. First, place four or five zebrafish into a 400 milliliter beaker containing 200 milliliters of sterile infection water. Then add one milliliter of V.cholerae culture for the desired infection concentration.Then, cover the beaker with a perforated lid. After preparing all the beakers, transfer them to a glass front incubator set at 28 degrees Celsius For a transitory exposure, after about six hours, pour out the beaker water through a fish net to collect the fish. The infected water must be disposed of in bleach to kill the bacteria.Then, place the fish into 200 milliliters of sterile infection water for five minutes. After five minutes, run this water through a fishnet, disposing of the water in bleach. Now, the fish can go into a new clean beaker with 200 milliliters of sterile infection water.When the experiment has reached its desired endpoint, take a 15 milliliter sample of the infection water for diagnostic purposes. Then collect the fish and dispose of the infected water appropriately. Orient the ventral side up and secure the body with a pin through the lower jaw and another pin just posterior to the anus.Angle both pins away from the body. Next, wipe off the ventral surface of the fish with 70%ethanol. Then, sterilize a scalpel and Vannas scissors by using 70%ethanol and a flame.Now, using the scalpel, make a small lengthwise incision in the belly that penetrates the scales, but only cut as deep as the skin. Next, with the scissors, extend the incision carefully along the length of the body, cutting no deeper than skin level. Avoid cutting the anus.Then make two lateral cuts towards the head to expand the opening. Then, pin the skin on each side of the lateral incisions to the dissecting surface, angling the pins out, away from the body. The intestinal tract should now be visible as a very thin, pale tube.Now, use two pair of flame sterilized forceps to carefully remove the entire intestinal tract which can be quite fragile. Transfer the tissue into a hominization tube containing glass beads and one milliliter of cold buffer. Next, homogenize the tissues as described in the text protocol and quantify the intestinal colonization levels.Next, make serial dilutions of the intestinal homogenate and buffer. For each fish, prepare five or six ten fold dilutions in one milliliter volumes. Vortex the tubes for mixing.Then, plate 100 to 200 microliters of each dilution on LB agar plates containing streptomycin and X-gal. Incubate the plates at 30 degrees Celsius for 16 to 18 hours. After the overnight incubation, count the V.cholerae colonies on the plates.These bacteria typically produce pale blue colonies on LB medium with X-gal. If several colony morphologies are observed, patch a few colonies of each different morphology onto a different TCBS plate. On TCBS, V.cholerae produces large, slightly flattened yellow colonies with opaque centers and translucent peripheries.To determine the mucin levels in fish diarrhea, perform an assay on a 96 well plate. In triplicate, load 100 microliters of infection water for each test condition, including a blank, into the wells. Then, mix in 50 microliters of fresh, 0.1%periodic acid solution into each test well.Use pipetting to mix. Next, wrap the plate tightly in plastic and incubate the plate at 37 degrees Celsius for one to one and a half hours. After the incubation, cool the plate down to room temperature.Into each well, add 100 microliters of Fuchsin solution and mix with pipetting. Now, rewrap the plate and put it on a rocker at room temperature. In about 20 minutes, read the plate at 560 nanometers using a plate reader.To quantify the reaction caused by mucin in solution. To measure protein levels in fish diarrhea use the Bradford assay. Mix 66 microliters of one of the BSA standards or 66 microliters of infection water with 1, 000 microliters of Bradford assay reagent in a disposable cuvette.Now, incubate the samples at room temperature for two minutes. And then read the absorbance at 660 nanometers on a spectrophotometer. A simple metric for the amount of diarrhea is the turbidity in the water measured at 600 nanometers.Mix the water well, add one milliliter to a disposable cuvette and take a measurement. For a baseline, blank measurement, use a clean infection water. The excreted V.cholerae bacteria can also be measured.This can be done with fish that have been moved to clean water after being inoculated. Make serial dilutions of an aliquat of tank water as previously described. Then plate the dilutions on selective media and incubate the plates at 30 degrees Celsius for 24 hours.Later, count the colonies as previously described and then determine the CFU. Groups of zebrafish housed in 200 milliliters of water were inoculated with five million CFU of a pandemic cholerae. After six hours in the bacteria infested water, the fish move to clean water for 18 hours.The air intestines were then harvested. Each fish harbored an estimated 100, 000 to 1, 000, 000 V.cholerae cells. The infection water was used for other assays.Mucin levels were higher when the infectious doses were higher. The OD600 of the water was significantly higher when fish were infected with V.cholerae. Finally, the total protein level in the infected fish water was nearly twice that observed in the water of the uninfected fish.After watching this video, you should have a good understanding of how to infect adult zebrafish with vibrio cholerae and quantify diarrhea induced by the infection. Following this procedure, other methods, like transmission assays, can be performed to assess infection of naive fish by previously infected fish.

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JoVE Journal

Immunology and Infection

8.2K vistas.  Wayne State University School of Medicine. This method can help answer key questions in the vibrio cholerae field, such as how the vibrio cholerae colonizes in the Quiet Coast and competes with the intestinal microbiota to establish a niche. The main advantage of this technique is that fish are a natural vibrio cholerae host so we can study the complete vibrio cholerae life cycle. Demonstrating the procedure will be Dhrubajyoti Nag, a postdoc from my laboratory and Paul Breen, a Ph.D.student from my laboratory.After preparing t...