Name: murine oropharyngeal aspiration model of ventilator-associated and hospital-acquired bacterial pneumonia
Uploaded: 2018-06-28T14:00:00
Description: Watch this Scientific Journal Video about Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia at JoVE.com

This work was supported by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health [Grant Numbers R01 AI117211, R01 AI130060, R21 AI127954, and R42 AI106375 to BS] and US Food and Drug Administration [Contract HHSF223201710199C to BML].

All procedures involving animals must be approved by the researcher&#8217;s Institutional Animal Care and Use Committee (IACUC).
1. Preparation of Bacterial Inoculum
<ol>
	<li>Isolate bacterial colonies.
	<ol>
		<li>Streak a bacterial strain (e.g., A. baumannii &#8220;HUMC1&#8221;) on appropriate sterile agar medium (e.g., Tryptic soy agar), being careful to generate isolated colonies.</li>
		<li>Incubate at appropriate conditions (e.g., overnight at 37 &#...

<ol>
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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=Management+of+Adults+With+Hospital-acquired+and+Ventilator-associated+Pneumonia:+2016+Clinical+Practice+Guidelines+by+the+Infectious+Diseases+Society+of+America+and+the+American+Thoracic+Society.">Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society.</a> Clinical Infectious Diseases. 63 (5), e61-e111 (2016).</li><li>Medina, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Murine+model+of+pneumococcal+pneumonia.">Murine model of pneumococcal pneumonia.</a> Methods in Molecular Biology. , 405-410 (2010).</li><li>Azoulay-Dupuis, E., 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=In+vivo+efficacy+of+a+new+fluoroquinolone,+sparfloxacin,+against+penicillin-susceptible+and+-resistant+and+multiresistant+strains+of+Streptococcus+pneumoniae+in+a+mouse+model+of+pneumonia.">In vivo efficacy of a new fluoroquinolone, sparfloxacin, against penicillin-susceptible and -resistant and multiresistant strains of Streptococcus pneumoniae in a mouse model of pneumonia.</a> Antimicrobial Agents and Chemotherapy. 36 (12), 2698-2703 (1992).</li><li>Mizgerd, J. P., Skerrett, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+human+pneumonia.">Animal models of human pneumonia.</a> American Journal of Physiology-Lung Cellular and Molecular Physiology. 294 (3), L387-L398 (2008).</li><li>Rayamajhi, 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=Non-surgical+intratracheal+instillation+of+mice+with+analysis+of+lungs+and+lung+draining+lymph+nodes+by+flow+cytometry.">Non-surgical intratracheal instillation of mice with analysis of lungs and lung draining lymph nodes by flow cytometry.</a> Journal of Visualized Experiments. (51), (2011).</li><li>Nielsen, T. B., Bruhn, K. W., Pantapalangkoor, P., Junus, J. L., Spellberg, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+virulent+Acinetobacter+baumannii+to+reduce+variability+of+in+vivo+studies.">Cryopreservation of virulent Acinetobacter baumannii to reduce variability of in vivo studies.</a> BMC Microbiology. 15, 252 (2015).</li><li>Trammell, R. A., Toth, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Markers+for+predicting+death+as+an+outcome+for+mice+used+in+infectious+disease+research.">Markers for predicting death as an outcome for mice used in infectious disease research.</a> Comparative Medicine. 61 (6), 492-498 (2011).</li><li>Bast, D. J., 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=Novel+murine+model+of+pneumococcal+pneumonia:+use+of+temperature+as+a+measure+of+disease+severity+to+compare+the+efficacies+of+moxifloxacin+and+levofloxacin.">Novel murine model of pneumococcal pneumonia: use of temperature as a measure of disease severity to compare the efficacies of moxifloxacin and levofloxacin.</a> Antimicrobial Agents and Chemotherapy. 48 (9), 3343-3348 (2004).</li><li>Hankenson, F. 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=Weight+loss+and+reduced+body+temperature+determine+humane+endpoints+in+a+mouse+model+of+ocular+herpesvirus+infection.">Weight loss and reduced body temperature determine humane endpoints in a mouse model of ocular herpesvirus infection.</a> Journal of the American Association for Laboratory Animal Science. 52 (3), 277-285 (2013).</li><li>Adamson, T. W., Diaz-Arevalo, D., Gonzalez, T. M., Liu, X., Kalkum, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hypothermic+endpoint+for+an+intranasal+invasive+pulmonary+aspergillosis+mouse+model.">Hypothermic endpoint for an intranasal invasive pulmonary aspergillosis mouse model.</a> Comparative Medicine. 63 (6), 477-481 (2013).</li><li>Nielsen, T. 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=Diabetes+Exacerbates+Infection+via+Hyperinflammation+by+Signaling+through+TLR4+and+RAGE.">Diabetes Exacerbates Infection via Hyperinflammation by Signaling through TLR4 and RAGE.</a> mBio. 8 (4), (2017).</li><li>Nielsen, T. 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=Monoclonal+Antibody+Protects+Against+Acinetobacter+baumannii+Infection+by+Enhancing+Bacterial+Clearance+and+Evading+Sepsis.">Monoclonal Antibody Protects Against Acinetobacter baumannii Infection by Enhancing Bacterial Clearance and Evading Sepsis.</a> Journal of Infectious Diseases. 216 (4), 489-501 (2017).</li><li>Cheng, B. 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=Evaluation+of+serotypes+5+and+8+capsular+polysaccharides+in+protection+against+Staphylococcus+aureus+in+murine+models+of+infection.">Evaluation of serotypes 5 and 8 capsular polysaccharides in protection against Staphylococcus aureus in murine models of infection.</a> Human Vaccine Immunotherapy. 13 (7), 1609-1614 (2017).</li><li>Wong, 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=Clinical+and+Pathophysiological+Overview+of+Acinetobacter+Infections:+a+Century+of+Challenges.">Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges.</a> Clinical Microbiology Reviews. 30 (1), 409-447 (2017).</li></ol>

To be sure, mice are not miniature humans. Results obtained from mouse models must be considered in context and subsequently interpreted for applicability to humans, based on differences and similarities between the two species6. It is also important to choose the appropriate mouse strain as certain are more susceptible to some infections than others; the same applies to the pathogen strain of choice16.
It is essential to perform infections in an...

Lower respiratory infection is the world&#39;s deadliest communicable disease and the most common cause of death in developing countries1. Globally, these infections account for more than 3.2 million deaths1. In addition, nosocomial pneumonia is among the most common and deadly forms of healthcare acquired infections, and is caused by the most antibiotic-resistant pathogens2,3. The typical route of acquisition of bacterial pneumonia for both community-acquired and nosocomial pneumonia is the aspiration of oropharyngeal contents into the alveoli. Murine models used to study these diseases often use intranasal inoculation4, depositing much of the bacteria outside the lung, causing off-target complications and symptoms like sinusitis and physical trauma, which are incongruent with the disease progression in human that the models were designed to emulate. Other models may use inhalation chambers and micromisting devices, which more accurately mimic viral, tuberculous, and fungal pneumonias, but do not accurately recapitulate the normal route of acquisition for typical bacterial pneumonias.
The murine oropharyngeal aspiration pneumonia model may be utilized to simulate the natural route and pathogenesis of bacterial pneumonia. By inoculating 50 &#181;L of the bacterial suspension into the oropharynx of anesthetized mice using a pipette, reflexive aspiration ensues, which results in infectious pneumonia. Using this model, one can examine the pathogenesis of pneumonia-causing pathogens and new treatments to combat these diseases with a higher fidelity model, more analogous to aspiration pneumonia infections observed in human. Additionally, unlike similar models that infect through the oral cavity5,6, this model ensures that the full inoculum reaches the lungs instead of the gut, where it can cause off-site inflammation and infections, such as gastritis and enteritis. Finally, unlike another published model that requires a laryngoscope and inoculates through the trachea7, this model does not obstruct the airway with a gavage needle and does not require injection for inoculum delivery. Instead, inoculation relies on the natural aspiration reflex of the mouse.

<table>
	<tbody>
		<tr>
			<td>Agar</td>
			<td>BD</td>
			<td>214530</td>
			<td>Combine with TSB to make TSA</td>
		</tr>
		<tr>
			<td>Beads, Borosilicate Glass</td>
			<td>Kimble</td>
			<td>135003</td>
			<td>Sterilize by baking or autoclaving before each use</td>
		</tr>
		<tr>
			<td>Beaker, 250 mL</td>
			<td>Pyrex</td>
			<td>1003</td>
			<td>Used during precise aliquoting of concentrated bacterial inocula</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Sorvall</td>
			<td>ST 40R</td>
			<td>Capable of 4,000&#215;g at 4&#176;C</td>
		</tr>
		<tr>
			<td>Chamber for Anesthesia</td>
			<td>Kent Scientific Corporation</td>
			<td>VetFlo-0720</td>
			<td>Accommodates up to 5 mice</td>
		</tr>
		<tr>
			<td>Cryomold, Intermediate Size</td>
			<td>Sakura Tissue-Tek</td>
			<td>4566</td>
			<td>Disposable vinyl specimen molds, 15&#215;15&#215;5 mm</td>
		</tr>
		<tr>
			<td>Dental Floss</td>
			<td>Oral-B</td>
			<td>37000469537</td>
			<td>Tie to stable post approx. 6&#34; above table height</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>VWR</td>
			<td>82027-440</td>
			<td>Used to gently pull tongue out of mouse&#39;s mouth</td>
		</tr>
		<tr>
			<td>Homogenizer for Lung Tissue</td>
			<td>Omni International</td>
			<td>TM125-115</td>
			<td>Autoclave before first use; rinse between samples</td>
		</tr>
		<tr>
			<td>Isoflurane for Anesthesia</td>
			<td>Abbott</td>
			<td>10015516</td>
			<td>Alternative drug can be used; modify procedure accordingly</td>
		</tr>
		<tr>
			<td>iSTAT Cartridge</td>
			<td>Abbott</td>
			<td>03P79-25</td>
			<td>Various cartridges are available to suit your needs</td>
		</tr>
		<tr>
			<td>Ketamine, 100 mg/mL</td>
			<td>Western Medical Supply</td>
			<td>4165</td>
			<td>Dilute 1:10 in PBS to 1 mg/mL and combine with Xylazine at 1 mg/mL</td>
		</tr>
		<tr>
			<td>Ointment for Eyes</td>
			<td>Akorn</td>
			<td>Tears Renewed</td>
			<td>Avoid touching eye with tip of dispenser</td>
		</tr>
		<tr>
			<td>Optimal Cutting Temperature (O.C.T.) Compound</td>
			<td>Fisher Scientific</td>
			<td>23-730-571</td>
			<td>Used to freeze lung samples at -80 &#176;C to prepare for pathology sectioning</td>
		</tr>
		<tr>
			<td>Petri Dish</td>
			<td>VWR</td>
			<td>25384-302</td>
			<td>Polystyrene, disposable, sterilized, 100&#215;15 mm</td>
		</tr>
		<tr>
			<td>Phosphate-Buffered Saline (PBS)</td>
			<td>Corning</td>
			<td>21-031-CM</td>
			<td>Dulbecco&#39;s PBS without calcium and magnesium</td>
		</tr>
		<tr>
			<td>Pipette Tips, 200-&#956;L</td>
			<td>VWR</td>
			<td>10017-044</td>
			<td>Autoclave before use</td>
		</tr>
		<tr>
			<td>Pipetter, 200-&#956;L</td>
			<td>Gilson</td>
			<td>Pipetman P200</td>
			<td>Autoclave and calibrate before use</td>
		</tr>
		<tr>
			<td>Spreader, Bacterial Cell</td>
			<td>Bel-Art</td>
			<td>F377360006</td>
			<td>Sterilize by baking or autoclaving before each use</td>
		</tr>
		<tr>
			<td>Stir Bar, Magnetic, 7.9 mm Diameter &#215; 38.1 mm Length</td>
			<td>VWR</td>
			<td>58948-150</td>
			<td>Used for stiring concentrated bacterial inocula during aliquoting</td>
		</tr>
		<tr>
			<td>Stir Plate, Magnetic</td>
			<td>Corning</td>
			<td>PC-620D</td>
			<td>Used for stiring concentrated bacterial inocula during aliquoting</td>
		</tr>
		<tr>
			<td>Tryptic Soy Broth (TSB)</td>
			<td>BD</td>
			<td>211822</td>
			<td>Combine with Agar to make TSA</td>
		</tr>
		<tr>
			<td>Vial, Conical, Sterile, 50 mL</td>
			<td>Corning</td>
			<td>431720</td>
			<td>Used for preparing bacterial inocula</td>
		</tr>
		<tr>
			<td>Vial, Conical, Sterile, 500 mL</td>
			<td>Corning</td>
			<td>431123</td>
			<td>Used to concentrate inocula for preparing frozen inocula</td>
		</tr>
		<tr>
			<td>Vial, Cryogenic, 2.0 mL</td>
			<td>Corning</td>
			<td>430659</td>
			<td>Used for cryogenic storage of concentrated bacterial inocula</td>
		</tr>
		<tr>
			<td>Xylazine, 20 mg/mL</td>
			<td>Akorn</td>
			<td>AnaSed Injection</td>
			<td>Dilute 1:20 in PBS to 1 mg/mL and combine with Ketamine at 1 mg/mL</td>
		</tr>
	</tbody>
</table>

murine oropharyngeal aspiration model of ventilator-associated and hospital-acquired bacterial pneumonia

Murine infection models are critical for understanding disease pathogenesis and testing the efficacy of novel therapeutics designed to combat causative pathogens. Infectious pneumonia is among the most common infections presented by patients in the clinic and thus warrants an appropriate in vivo model. Typical pneumonia models use intranasal inoculation, which deposits excessive organisms outside the lung, causing off-target complications and symptoms, such as sinusitis, gastritis, enteritis, physical trauma, or microparticle misting to mimic aerosol spread more typical of viral, tuberculous, or fungal pneumonia. These models do not accurately reflect the pathogenesis of typical community- or healthcare-acquired bacterial pneumonia. In contrast, this murine model of oropharyngeal aspiration pneumonia mimics the droplet route in healthcare-acquired pneumonia. Inoculating 50 &#181;L of the bacteria suspension into the oropharynx of anesthetized mice causes reflexive aspiration, which results in pneumonia. With this model, one can examine the pathogenesis of pneumonia-causing pathogens and new treatments to combat these diseases.

By carefully following the protocol, reproducible and robust data can be easily obtained. It is critical to strictly adhere to one&#39;s customized inoculum preparation protocol for experiments to be compared to one each other. It is also important to properly handle mice during the infection procedure. Be sure to place mice into an anesthesia chamber devoid of isoflurane. Mice will panic if they are placed into a chamber that has been pre-filled with isoflurane and may experience excess ...

Watch this Scientific Journal Video about Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia at JoVE.com

Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia

Infectious pneumonia is among the most common infections in human. An appropriate in vivo model is critical for understanding disease pathogenesis and testing the efficacy of novel therapeutics. With this murine oropharyngeal aspiration pneumonia model, one can examine the pathogenesis and new treatments against these deadly infections.

Murine infection models are critical for understanding disease pathogenesis and testing the efficacy of novel therapeutics designed to combat causative ...

This method can help answer key questions in the field of antibiotic resistance about novel therapeutics with a treatment of ventilator-associated pneumonia. The main advantage of this technique is that it accurately replicates clinical infection in a quick and easily reproducible manner. To inoculate the mice, hang the first anesthetized animal by its top incisors on a strong thin string.Secure it to a fixed object above the operating surface, at a height approximately twice the mouse's body length. Use sterile blunt-handed forceps to gently pull out the tongue, and transfer the tongue to sterile, gloved fingers to allow access to the oral pharynx. Depress the plunger of a micro pipette to the first stop to place 50 microliters of the inoculum into the oral pharynx, until the mouse inhales the bacterial suspension, by reflexive aspiration.The mouse will stop breathing for a few seconds when the inoculum is placed in the oral pharynx, and eventually reflexive aspiration will cause the bacterial suspension to be inhaled, indicative by the distinctive crackling noise of liquid entering the lungs. Then return the animal to its cage, with monitoring, until full recumbency. At the appropriate experimental endpoint, cut the trachea, pulmonary artery, and pulmonary vein, to allow removal of the lung tissue.For histopathological analysis of the disease progression, place the lungs into a specimen mold. And fill the mold with optimal cutting temperature compound, until the tissue is completely submerged. Then freeze the samples at minus 80 degrees Celsius, until their sectioning and analysis.To estimate the bacterial burden, transfer the harvested lung tissue to a 50 milliliter conical vial, and determine its mass with an analytical balance. Then transfer five milliliters of sterile PBS to the vial. Homogenize the lung tissue with a tissue homogenizer.And perform serial dilutions in the homogenate and sterile PBS, to achieve approximately 1000 colony forming units, or CFU, per millimeter, based on the expected bacterial burden in the infected lungs. Plate 100 microliters of each dilution onto individual tryptic soy agar plates. And use glass beads to evenly distribute the homogenates.Then store the plates in a humidified, 37 degree Celsius incubator over night. Before calculating the number of colony forming units per dilution. It is necessary to infect the mice with various inoculum concentrations, to determine the LD 100.Under these representative experimental conditions, two times 10 to the eighth CFU per mouse was too high. Five times 10 to the seventh and two times 10 to the seventh, were too low. And one times 10 to the eighth was just right Hematoxylin and ee-ah-zin staining of lung sections before and 24 hours after oral pharyngeal aspiration of the bacterial species commonly encountered in ventilator-associated pneumonia in humans, typically results in substantial alveolar inflammation.While attempting this procedure, it's important to remember the inoculum must be prepared and atomy surd identically from experiment to experiment to obtain reproducible results. After watching this video, you should have a good understanding of how to recapitulate ventilator-associated pneumonia using a mouse model.

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