Name: studying microbial communities in vivo: a model of host-mediated interaction between candida albicans and pseudomonas aeruginosa in the airways
Uploaded: 2016-01-13T14:00:00
Description: Watch this Scientific Journal Video about Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways at JoVE.com

The authors would like to acknowledge the University of Lille and the Pasteur Institute of Lille, especially Thierry Chassat and Jean-Pierre Decavel, responsible for animal housing breeding safety and husbandry. This work was supported by the "Soci&#233;t&#233; de Pathologies Infectieuses de Langue Fran&#231;aise" (SPILF).

The regional ethics regional committee for animal experiments has approved this method, in accordance with national and international animal care and use in investigational research guidelines.
1. Sample Collection
<ol>
	<li>Sample storage
	<ol>
		<li>Collect all samples and immediately store at - 20 &#176;C or on ice until freezer storage to avoid deterioration. Place sterile phosphate buffered saline (PBS) on ice to improve broncho-alveolar lavages (BAL) performance.</li>
	</ol>
	</li>
	<l...

<ol>
	<li>Casadevall, A., Pirofski, 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=The+damage-response+framework+of+microbial+pathogenesis.">The damage-response framework of microbial pathogenesis.</a> Nat. Rev. Micro. 1 (1), 17-24 (2003).</li><li>Eddens, T., Kolls, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+defenses+against+bacterial+lower+respiratory+tract+infection.">Host defenses against bacterial lower respiratory tract infection.</a> Curr. Opi. Immunol. , (2012).</li><li>Beck, J. M., Young, V. B., Huffnagle, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+microbiome+of+the+lung.">The microbiome of the lung.</a> Translational research : J. Lab. Clin Med. 160 (4), 258-266 (2012).</li><li>Hogan, D. A., Kolter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pseudomonas-Candida+interactions:+an+ecological+role+for+virulence+factors.">Pseudomonas-Candida interactions: an ecological role for virulence factors.</a> Science. 296 (5576), 2229-2232 (2002).</li><li>Nseir, S., Ader, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pseudomonas+aeruginosa+and+Candida+albicans:+do+they+really+need+to+stick+together.">Pseudomonas aeruginosa and Candida albicans: do they really need to stick together.</a> Crit. Care Med. 37 (3), 1164-1166 (2009).</li><li>Hibbing, M. E., Fuqua, C., Parsek, M. R., Peterson, 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=Bacterial+competition:+surviving+and+thriving+in+the+microbial+jungle.">Bacterial competition: surviving and thriving in the microbial jungle.</a> Nat. Rev. Micro. 8 (1), 15-25 (2010).</li><li>Gibbons, D. L., Spencer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+and+human+intestinal+immunity:+same+ballpark,+different+players;+different+rules,+same+score.">Mouse and human intestinal immunity: same ballpark, different players; different rules, same score.</a> Mucosal Immunol. 4 (2), 148-157 (2011).</li><li>Ariffin, J. K., Sweet, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+the+repertoire,+regulation+and+function+of+Toll-like+Receptors+and+inflammasome-forming+Nod-like+Receptors+between+human+and+mouse.">Differences in the repertoire, regulation and function of Toll-like Receptors and inflammasome-forming Nod-like Receptors between human and mouse.</a> Curr. Opi. Micro.. , (2013).</li><li>Slutsky, A. S., Ranieri, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventilator-Induced+Lung+Injury.">Ventilator-Induced Lung Injury.</a> NEJM. 369 (22), 2126-2136 (2013).</li><li>Peleg, A. Y., Hogan, D. A., Mylonakis, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Medically+important+bacterial-fungal+interactions.">Medically important bacterial-fungal interactions.</a> Nat. Rev. Micro. 8 (5), 340-349 (2010).</li><li>Roux, D., Gaudry, S., 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=Candida+albicans+impairs+macrophage+function+and+facilitates+Pseudomonas+aeruginosa+pneumonia+in+rat.">Candida albicans impairs macrophage function and facilitates Pseudomonas aeruginosa pneumonia in rat.</a> Crit. Care Med. 37 (3), 1062-1067 (2009).</li><li>Mear, J. B., Gosset, P., 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=Candida+albicans+Airway+Exposure+Primes+the+Lung+Innate+Immune+Response+against+Pseudomonas+aeruginosa+Infection+through+Innate+Lymphoid+Cell+Recruitment+and+Interleukin-22-Associated+Mucosal+Response.">Candida albicans Airway Exposure Primes the Lung Innate Immune Response against Pseudomonas aeruginosa Infection through Innate Lymphoid Cell Recruitment and Interleukin-22-Associated Mucosal Response.</a> Infect. Immun. 82 (1), 306-315 (2013).</li><li>Ader, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short+term+Candida+albicans+colonization+reduces+Pseudomonas+aeruginosa+load+and+lung+injury+in+a+mouse+model.">Short term Candida albicans colonization reduces Pseudomonas aeruginosa load and lung injury in a mouse model.</a> Crit. care. , 1-33 (2009).</li><li>Risling, T. E., Caulkett, N. A., Florence, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Open-drop+anesthesia+for+small+laboratory+animals.">Open-drop anesthesia for small laboratory animals.</a> Can Vet J. 53 (3), 299-302 (2012).</li><li>Stover, C. K., Pham, X. Q., 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=Complete+genome+sequence+of+Pseudomonas+aeruginosa+PAO1,+an+opportunistic+pathogen.">Complete genome sequence of Pseudomonas aeruginosa PAO1, an opportunistic pathogen.</a> Nature. 406 (6799), 959-964 (2000).</li><li>Boutoille, D., Marechal, X., Pichenot, M., Chemani, C., Guery, B. P., Faure, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FITC-albumin+as+a+marker+for+assessment+of+endothelial+permeability+in+mice:+comparison+with+125I-albumin.">FITC-albumin as a marker for assessment of endothelial permeability in mice: comparison with 125I-albumin.</a> Exp. Lung Res. 35 (4), 263-271 (2009).</li><li>Faure, E., Mear, J. -. 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=Pseudomonas+aeruginosa+type-3+secretion+system+dampens+host+defense+by+exploiting+the+NLRC4-coupled+inflammasome.">Pseudomonas aeruginosa type-3 secretion system dampens host defense by exploiting the NLRC4-coupled inflammasome.</a> American Journal of Respiratory and Critical Care Medicine. 189 (7), 799-811 (2014).</li><li>Peleg, A. Y., Hogan, D. A., Mylonakis, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Medically+important+bacterial-fungal+interactions.">Medically important bacterial-fungal interactions.</a> Nat. Rev. Micro. 8 (5), 340-349 (2010).</li></ol>

Animal models, particularly mammals, are useful to elucidate complex mechanisms of host-pathogen interaction in the fields of immunity. Of course, the need for information obtainable only from animal models must be essential; otherwise, use of animals must be replaced by in vitro models. This animal model illustrates the insight that can only be provided by an animal model since the interaction between pathogens is mediated by a multi-component host response. Mice currently used to study this host-pathogen inter...

Animal models, especially mice, have been extensively used to explore immune responses against pathogens. Although innate and acquired immunity differ between rodents and humans7, the ease in breeding and the development of knockouts for numerous genes, make mice an excellent model to study immune responses8. The immune response is complex and results from the interaction of a pathogen, the resident microbial flora and several immune (lymphocytes, neutrophils, macrophages) and non-immune (epithelial cells, endothelial cells) cellular types2. In vitro studies do not allow observing these complex interactions and mainly focus on unique cell-pathogen interactions. While animal models must be used with caution and limited to very specific and relevant questions, mouse models provide a good insight into the mammal immune response in vivo and may address parts of important clinical questions7.
In the airways, the microbial community is complex associating a large number of different microorganisms6. While what constitutes a &#34;normal&#34; airway microbiome remains to be determined, resident communities are frequently polymicrobial, and originate from diverse ecological sources. Patients with suppurative chronic lung disease (cystic fibrosis, bronchectasis) or mechanically ventilated patients exhibit a particular flora due to colonization of the airways by environmentally-acquired microorganisms9. Pseudomonas aeruginosa and Candida albicans are both problem pathogens5, frequently isolated together from tracheobronchial samples, and responsible of severe opportunistic infection in these patients, especially in the intensive care unit (ICU)4.
Isolation of these microorganisms during acute pneumonia in ICU results in anti-microbial treatment against P. aeruginosa but yeast are usually not considered pathogenic at this site5. In vitro interactions between P. aeruginosa and C. albicans have been widely reported and showed that these microorganisms can affect the growth and the survival of each other but studies could not conclude if the presence of C. albicans is detrimental or beneficial for the host10. Mouse models were developed to address this relevance of P. aeruginosa&#160;and C. albicans&#160;in vivo, but the interaction between microorganisms was not the key point. Indeed, the model was established to evaluate the involvement of C. albicans in host immune response, and outcome.
A previous model established by Roux et al already used an initial colonization with C. albicans followed by an acute lung infection induced by P. aeruginosa. Using their model, the authors found a deleterious role of prior C. albicans colonization11. However Roux et al used a high load of C. albicans in their model with 2 x 106 CFU/mouse during 3 consecutive days. We established a 4-day model of C. albicans airway colonization, or at least persistence without lung injury, In this model C. albicans was retrieved up to 4 days after a single instillation of 105 CFU per mouse (Figure 2B) 12,13. After 4 days, no evidence of inflammatory cell recruitment, inflammatory cytokine production nor epithelial damage was observed. At 24 - 48 hr, at the peak presence of C. albicans, even though a cellular and cytokine innate immune response was observed, there was no evidence of lung injury. Surprisingly, mice thus colonized with C. albicans 48 hr prior to intranasal instillation of P. aeruginosa had attenuated infection compared to mice with P. aeruginosa infection alone. Indeed, mice exhibited lesser lung injury and decreased bacterial burden12,13.
Several hypotheses could explain this beneficial effect of prior colonization with C. albicans on P. aeruginosa-mediated acute lung infection. First, an interspecies cross-talk involving each microorganisms quorum-sensing systems, the homoserinelactone-based P. aeruginosa system and the farnesol-based C. albicans system, were evaluated. Second, C. albicans acting as a &#34;decoy&#34; target for P. aeruginosa diverting the pathogen from lung epithelial cells was studied. Both hypotheses were invalidated (unpublished data). The third hypothesis was that of a &#34;priming&#34; of the innate immune system by C. albicans responsible for an enhanced subsequent innate response against P. aeruginosa. This last hypothesis was confirmed. Indeed C. albicans colonization led to a priming of innate immunity through IL-22, mainly secreted by innate lymphoid cells, resulting in increased bacterial clearance and reduced lung injury12.
In conclusion, the host is a central actor in the interaction between microorganisms modulating the innate immune response and involving different inflammatory cell types. While these complex immune interactions can be dissected in vitro the initial hypotheses can only be provided by appropriate in&#160;vivo models. The following protocol provides an example of in vivo study of host-mediated pathogen interaction that may be adapted to others microorganisms.

<table border="0" cellpadding="0" cellspacing="0" width="729">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sevorane, Sevoflurane</td>
			<td style="width:185px;">Abott</td>
			<td style="width:161px;">05458-02</td>
			<td style="width:167px;">250 mL plastic bottle</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Fluorescence Reader Mithras&#160; LB940</td>
			<td style="width:185px;">Berthold Technologies</td>
			<td style="width:161px;">reference in first column</td>
			<td>no comment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Bromo-cresol purple agar</td>
			<td style="width:185px;">Biomerieux</td>
			<td align="right" style="width:161px;">43021</td>
			<td>x20 per unit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pentobarbital sodique 5,47%</td>
			<td style="width:185px;">CEVA</td>
			<td align="right" style="width:161px;">6742145</td>
			<td>100 mL plastic bottle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2-headed valve&#160;</td>
			<td style="width:185px;">Distrimed</td>
			<td align="right" style="width:161px;">92831</td>
			<td>no comment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sterile inoculation loop 10 &#181;L</td>
			<td style="width:185px;">Dutscher</td>
			<td align="right" style="width:161px;">10175</td>
			<td>x1000 conditioning</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Insuline syringes 1 mL</td>
			<td style="width:185px;">Dutscher</td>
			<td align="right" style="width:161px;">30003</td>
			<td>per 100 conditioning</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2 positions Culture tube 8 mL</td>
			<td style="width:185px;">Dutscher</td>
			<td align="right" style="width:161px;">64300</td>
			<td>no comment</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrospec 10&#160;</td>
			<td style="width:185px;">General Electric life sciences</td>
			<td style="width:161px;">80-2116-30</td>
			<td>no comment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hemolysis tubes 13 x 75 mm&#160;</td>
			<td style="width:185px;">Gosselin</td>
			<td style="width:161px;">W1773X</td>
			<td>per 100</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">PBS - Phosphate-Buffered Saline</td>
			<td style="width:185px;">Life technologies</td>
			<td align="right" style="width:161px;">10010023</td>
			<td>packaged in 500 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">amikacin 1g</td>
			<td style="width:185px;">Mylan</td>
			<td align="right" style="width:161px;">62516778</td>
			<td>per 10&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Heparin 10 000 UI in 2 mL</td>
			<td style="width:185px;">Pan pharma</td>
			<td align="right" style="width:161px;">9128701</td>
			<td>x 10 per unit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">RAL 555 coloration kit</td>
			<td style="width:185px;">RAL Diagnostics</td>
			<td align="right" style="width:161px;">361550</td>
			<td>3 flacons of 100 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">1,5 mL microcentrifuge tube</td>
			<td style="width:185px;">Sarstedt</td>
			<td style="width:161px;">55.526.006</td>
			<td>x&#160; 1000</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Transparent 300 &#181;L 96-well plate</td>
			<td style="width:185px;">Sarstedt</td>
			<td style="width:161px;">82 1581500</td>
			<td>no comment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Yest-peptone-Dextrose Broth</td>
			<td style="width:185px;">Sigma</td>
			<td align="right" style="width:161px;">95763</td>
			<td>in powder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">FITC-albumin</td>
			<td style="width:185px;">Sigma</td>
			<td style="width:161px;">A9771</td>
			<td>in powder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Luria Bertani Broth</td>
			<td style="width:185px;">Sigma</td>
			<td style="width:161px;">L3022</td>
			<td>in powder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">25-gauge needle</td>
			<td style="width:185px;">Terumo or unisharp</td>
			<td style="width:161px;">A231</td>
			<td>x100 conditioning</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cytocentrifuge</td>
			<td style="width:185px;">Thermo Scientific</td>
			<td style="width:161px;">A78300003</td>
			<td>no comment</td>
		</tr>
	</tbody>
</table>

studying microbial communities in vivo: a model of host-mediated interaction between candida albicans and pseudomonas aeruginosa in the airways

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of the host depends on the involvement of an adapted immune response against the pathogen1. Immune response is complex and results from interaction of the pathogens and several immune or non-immune cellular types2. In vitro studies cannot characterise these interactions and focus on cell-pathogen interactions. Moreover, in the airway3, particularly in patients with suppurative chronic lung disease or in mechanically ventilated patients, polymicrobial communities are present and complicate host-pathogen interaction. Pseudomonas aeruginosa and Candida albicans are both problem pathogens4, frequently isolated from tracheobronchial samples, and associated to severe infections, especially in intensive care unit5. Microbial interactions have been reported between these pathogens in vitro but the clinical impact of these interactions remains unclear6. To study the interactions between C. albicans and P. aeruginosa, a murine model of C. albicans airways colonization, followed by a P. aeruginosa-mediated acute lung infection was performed.

As seen previously during the protocol description, the experiment needs 5 day to complete (Figure 1: experiment timeline). One operator is solicited during the entire run of the experiment and can handle the processes up to a maximum of 10 mice. If more animals are required, two persons are needed particularly for surgical sample collection. Indeed all samples must be collected in under 2 hr to avoid an increased passive alveolar-capillary leakage of FITC-labeled albumin in the last mice.
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Watch this Scientific Journal Video about Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways at JoVE.com

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

While in vitro study of host-pathogen interactions allow the characterization of specific immune responses, in vivo models are required to observe the effects of complex responses. Using Candida albicans exposure followed by Pseudomonas aeruginosa-mediated lung infection, we established a murine model of microbial interactions involved in ventilator-associated pneumonia pathogenicity.

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of ...

The overall goal of this procedure is to build a model to study the interactions between an individual bacterium and a single fungus. This message can help to answer key questions in the field of pathogen interactions, such as what factors are involved in cross-talk and interspecies dialect. The main advantage of this technique is the data generated from this in vivo model have clinical relevance.To intranasally install the fungus, first dilute two times ten to the sixth CFU of C.albicans per milliliter in sterile PBS. Next, after confirming the loss of the righting reflex in an adult hypotonic mouse, aspirate at least 50 microliters of the fungal suspension into a 200 microliter pipette. Now, grasp the mouse with one hand and turn the animal so that it is nestled on its back with its abdomen facing upright.When the mouse is in position, use the index finger of the hand holding the mouse to support the head, and the thumb to keep the jaw closed, and move the pipette tip close to the animal's nose. Then, carefully dispense a 50 microliter drop of fungus onto the nostrils, allowing the drop to be inhaled by the spontaneous breathing of the mouse. And place the mouse alone in a cage until it is fully recovered.Four days after C.albicans installation, shave the abdomen of the euthanized animal, followed by ethanol sterilization of the exposed skin. Next, use scissors to open the skin from the sternum to the mid-abdomen. Then, extend the incision along the rib cage on either side of the midline and fold back the skin on either side of the thorax.When the rib cage is visible, make a vertical incision on either side of the chest toward the clavicles, and use the sternum to recline the entire anterior chest wall to visualize the heart and lungs. Then, using a pre-heparinized syringe, puncture the heart next to the intraventricular artery, and withdraw a minimum of 500 microliters of blood. Place the blood sample on ice.Then, make a midline cervical incision to reveal the trachea. Carefully dissect the fascia around the trachea, followed by the placement of a suture under the trachea. Then, use a 20-gauge modified gavage needle to catheterize the trachea, securing the cannula with the previously placed suture.To perform a bronchoalveolar lavage, gently dispense 500 microliters of ice-cold PBS into the lung. Then, aspirate the lavage fluid and transfer the fluid into a two milliliter centrifuge tube on ice. After collecting two more 500 microliter samples, remove the lungs from the chest, and place a piece of lung into a 1.5 milliliter centrifuge tube for immediate storage at minus 80 degrees Celsius.Then, place another piece of lung tissue into a pre-weighed hemolysis tube containing PBS on ice. Finally, make an incision in the left side of the abdomen. Harvest the spleen into a second hemolysis tube containing one milliliter of PBS and place the tube on ice.A four days persistence model is obtained by intranasal installation of five times ten to the fifth CFU of C.albicans per mouse. During these four days, mice gain weight, but do not exhibit lung injury. As the CFU of the inoculum increases, however, so does the lung injury.With the maximum lung injury observed between 24 to 36 hours after infection. The bacterial burden, by contrast, demonstrates a one log CFU per milliliter decrease every 24 hours, with a cumulative bacterial dissemination increase observed over each day. In the bronchoalveolar lavage harvested from infected mice, neutrophils are widely recruited, with the differential cell count demonstrating a 90 percent neutrophil, 10 percent macrophage lymphocyte infiltrating immune cell population.Following this procedure, other methods like analysis of the bronchoalveolar lavage can be performed to answer additional questions about the characterization of the inflammatory response. After watching this video, you should have a good understanding of how to build a colonization Pseudomonas. Don't forget that working with luminescent Candida can be extremely hazardous, and the precautions, such as wearing protective gear to avoid droplet contamination, should always be taken while performing this procedure.

studying-microbial-communities-vivo-model-host-mediated-interaction

Research

JoVE Journal

Immunology and Infection

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

There is growing concern about the relevance of in vitro antimicrobial susceptibility tests when applied to isolates of P. aeruginosa from cystic fibrosis (CF) patients. Existing methods rely on single or a few isolates grown aerobically and planktonically. Predetermined cut-offs are used to define whether the bacteria are sensitive or resistant to any given antibiotic1. However, during chronic lung infections in CF, P. aeruginosa populations exist in biofilms and there is evidence that the environment is largely microaerophilic2. The stark difference in conditions between bacteria in the lung and those during diagnostic testing has called into question the reliability and even relevance of these tests3.
 Artificial sputum medium (ASM) is a culture medium containing the components of CF patient sputum, including amino acids, mucin and free DNA. P. aeruginosa growth in ASM mimics growth during CF infections, with the formation of self-aggregating biofilm structures and population divergence4,5,6. The aim of this study was to develop a microtitre-plate assay to study antimicrobial susceptibility of P. aeruginosa based on growth in ASM, which is applicable to both microaerophilic and aerobic conditions.
 An ASM assay was developed in a microtitre plate format. P. aeruginosa biofilms were allowed to develop for 3 days prior to incubation with antimicrobial agents at different concentrations for 24 hours. After biofilm disruption, cell viability was measured by staining with resazurin. This assay was used to ascertain the sessile cell minimum inhibitory concentration (SMIC) of tobramycin for 15 different P. aeruginosa isolates under aerobic and microaerophilic conditions and SMIC values were compared to those obtained with standard broth growth. Whilst there was some evidence for increased MIC values for isolates grown in ASM when compared to their planktonic counterparts, the biggest differences were found with bacteria tested in microaerophilic conditions, which showed a much increased resistance up to a &gt;128 fold, towards tobramycin in the ASM system when compared to assays carried out in aerobic conditions.
 The lack of association between current susceptibility testing methods and clinical outcome has questioned the validity of current methods3. Several in vitro models have been used previously to study P. aeruginosa biofilms7, 8. However, these methods rely on surface attached biofilms, whereas the ASM biofilms resemble those observed in the CF lung9 . In addition, reduced oxygen concentration in the mucus has been shown to alter the behavior of P. aeruginosa2 and affect antibiotic susceptibility10. Therefore using ASM under microaerophilic conditions may provide a more realistic environment in which to study antimicrobial susceptibility.

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

Current diagnostic antimicrobial susceptibility testing relies on the planktonic growth of isolates in nutrient rich, aerobic conditions. Here, we employ an alternative artificial sputum medium to study antimicrobial susceptibility of Pseudomonas aeruginosa biofilms under both aerobic and microaerophilic conditions more representative of the cystic fibrosis lung.

There  is growing concern about the relevance of in vitro antimicrobial  susceptibility tests when applied to isolates of P. aeruginosa from  cystic ...

Pseudomonas aeruginosa Induced Lung Injury Model

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. Here we have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa (P. aeruginosa or PA). Using this model, we were able to show lung inflammation at the early phase of injury. In addition, alveolar epithelial barrier leakiness was observed by analyzing bronchoalveolar lavage (BAL); and alveolar cell death was observed by Tunel assay using tissue prepared from injured lungs. At a later phase following injury, we observed cell proliferation required for the repair process. The injury was resolved 7 days from the initiation of P. aeruginosa injection. This model mimics the sequential course of lung inflammation, injury and repair during pneumonia. This clinically relevant animal model is suitable for studying pathology, mechanism of repair, following acute lung injury, and also can be used to test potential therapeutic agents for this disease.

Pseudomonas aeruginosa Induced Lung Injury Model

We have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa. This model mimics lung injury during pneumonia and is clinically relevant.

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. ...

Come to the Light Side: In Vivo Monitoring of Pseudomonas aeruginosa Biofilm Infections in Chronic Wounds in a Diabetic Hairless Murine Model

The presence of bacteria as structured biofilms in chronic wounds, especially in diabetic patients, is thought to prevent wound healing and resolution. Chronic mouse wounds models have been used to understand the underlying interactions between the microorganisms and the host. The models developed to date rely on the use of haired animals and terminal collection of wound tissue for determination of viable bacteria. While significant insight has been gained with these models, this experimental procedure requires a large number of animals and sampling is time consuming. We have developed a novel murine model that incorporates several optimal innovations to evaluate biofilm progression in chronic wounds: a) it utilizes hairless mice, eliminating the need for hair removal; b) applies pre-formed biofilms to the wounds allowing for the immediate evaluation of persistence and effect of these communities on host; c) monitors biofilm progression by quantifying light production by a genetically engineered bioluminescent strain of Pseudomonas aeruginosa, allowing real-time monitoring of the infection thus reducing the number of animals required per study. In this model, a single full-depth wound is produced on the back of STZ-induced diabetic hairless mice and inoculated with biofilms of the P. aeruginosa bioluminescent strain Xen 41. Light output from the wounds is recorded daily in an in vivo imaging system, allowing for in vivo and in situ rapid biofilm visualization and localization of biofilm bacteria within the wounds. This novel method is flexible as it can be used to study other microorganisms, including genetically engineered species and multi-species biofilms, and may be of special value in testing anti-biofilm strategies including antimicrobial occlusive dressings.

Come to the Light Side: In Vivo Monitoring of Pseudomonas aeruginosa Biofilm Infections in Chronic Wounds in a Diabetic Hairless Murine Model

Here we describe a novel diabetic murine model utilizing hairless mice for real-time, non-invasive, monitoring of biofilm wound infections of bioluminescent Pseudomonas aeruginosa. This method can be adapted to evaluate infection of other bacterial species and genetically modified microorganisms, including multi-species biofilms, and test the efficacy of antibiofilm strategies.

The presence of bacteria as structured biofilms in chronic wounds, especially in diabetic patients, is thought to prevent wound healing and resolution. ...

Visualization of Candida albicans in the Murine Gastrointestinal Tract Using Fluorescent In Situ Hybridization

Candida albicans is a fungal component of the gut microbiota in humans and many other mammals. Although C. albicans does not cause symptoms in most colonized hosts, the commensal reservoir does serve as a repository for infectious disease, and the presence of high fungal titers in the gut is associated with inflammatory bowel disease. Here, we describe a method to visualize C. albicans cell morphology and localization in a mouse model of stable gastrointestinal colonization. Colonization is established using a single dose of C. albicans in animals that have been treated with oral antibiotics. Segments of gut tissue are fixed in a manner that preserves the architecture of luminal contents (microorganisms and mucus) as well as the host mucosa. Finally, fluorescent in situ hybridization is performed using probes against fungal rRNA to stain for C. albicans and hyphae. A key advantage of this protocol is that it allows for simultaneous observation of C. albicans cell morphology and its spatial association with host structures during gastrointestinal colonization.

Visualization of Candida albicans in the Murine Gastrointestinal Tract Using Fluorescent In Situ Hybridization

The purpose of this protocol is to visualize Candida albicans cell shape and localization in the mammalian gastrointestinal tract.

Candida albicans is a fungal component of the gut microbiota in humans and many other mammals. Although C. albicans does not cause symptoms in most ...

A Delayed Inoculation Model of Chronic Pseudomonas aeruginosa Wound Infection

Pseudomonas aeruginosa (P. aeruginosa) is a major nosocomial pathogen of increasing relevance to human health and disease, particularly in the setting of chronic wound infections in diabetic and hospitalized patients. There is an urgent need for chronic infection models to aid in the investigation of wound pathogenesis and the development of new therapies against this pathogen. Here, we describe a protocol that uses delayed inoculation 24 hours after full-thickness excisional wounding. The infection of the provisional wound matrix present at this time forestalls either rapid clearance or dissemination of infection and instead establishes chronic infection lasting 7&#8211;10 days without the need for implantation of foreign materials or immune suppression. This protocol mimics a typical temporal course of post-operative infection in humans. The use of a luminescent P. aeruginosa strain (PAO1:lux) allows for quantitative daily assessment of bacterial burden for P. aeruginosa wound infections. This novel model may be a useful tool in the investigation of bacterial pathogenesis and the development of new therapies for chronic P. aeruginosa wound infections.

A Delayed Inoculation Model of Chronic Pseudomonas aeruginosa Wound Infection

We describe a delayed inoculation protocol for generating chronic wound infections in immunocompetent mice.

Pseudomonas aeruginosa (P. aeruginosa) is a major nosocomial pathogen of increasing relevance to human health and disease, particularly in the setting of ...

Clarifying and Imaging Candida albicans Biofilms

The microbial fungus Candida albicans can undergo a change from commensal colonization to virulence that is strongly correlated with its ability to switch from yeast-form growth to hyphal growth. Cells initiating this process become adherent to surfaces as well as to each other, with the resulting development of a biofilm colony. This commonly occurs not only on mucosal tissue surfaces in yeast infections, but also on medical implants such as catheters. It is well known that biofilm cells are resistant to antifungal drugs, and that cells that shed from the biofilm can lead to dangerous systemic infections. Biofilms range from heavily translucent to opaque due to refractive heterogeneity. Therefore, fungal biofilms are difficult to study by optical microscopy. To visualize internal structural, cellular, and subcellular features, we clarify fixed intact biofilms by stepwise solvent exchange to a point of optimal refractive index matching. For C. albicans biofilms, sufficient clarification is attained with methyl salicylate (n = 1.537) to enable confocal microscopy from apex to base in 600 &#181;m biofilms with little attenuation. In this visualization protocol we outline phase contrast refractometry, the growth of laboratory biofilms, fixation, staining, solvent exchange, the setup for confocal fluorescence microscopy, and representative results.

Clarifying and Imaging Candida albicans Biofilms

To view and quantify the internal features of Candida albicans biofilms, we prepare fixed intact specimens that are clarified by refractive index matching. Then, optical sectioning microscopy can be used to obtain three-dimensional image data though the full thickness of the biofilm.

The microbial fungus Candida albicans can undergo a change from commensal colonization to virulence that is strongly correlated with its ability to switch ...

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important role in the dissemination and pathogenesis of this opportunistic fungal pathogen. However, methods to visualize fungal hyphae in the GI tract in vivo are challenging which limits the understanding of environmental signals in controlling this morphogenesis process. The protocol described here demonstrates a novel ex vivo method for visualization of hyphal morphogenesis in gut homogenate extracts. Using an ex vivo assay, this study demonstrates that cecal contents from antibiotic treated mice, but not from untreated control mice, promote C. albicans hyphal morphogenesis in the gut content. Further, adding back specific groups of gut metabolites to the cecal contents from antibiotic-treated mice differentially regulates hyphal morphogenesis ex vivo. Taken together, this protocol represents a novel method to identify and investigate the environmental signals that control C. albicans hyphal morphogenesis in the GI tract.

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

The ex vivo assay described in this study using gut homogenate extracts and immunofluorescence staining represents a novel method to examine the hyphal morphogenesis of Candida albicans in the GI tract. This method can be utilized to investigate the environmental signals regulating morphogenetic transition in the gut.

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important ...

Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients

Early detection and eradication of Pseudomonas aeruginosa within the lungs of cystic fibrosis patients can reduce the chance of developing chronic infection. The development of chronic P. aeruginosa infections is associated with a decline in lung function and increased morbidity. Therefore, there is a great interest in elucidating the reasons for the failure to eradicate P. aeruginosa with antibiotic therapy which occurs in approximately 10-40% of pediatric patients. One of many factors that can affect host clearance of P. aeruginosa and antibiotic susceptibility is variations in spatial organization (such as aggregation or biofilm formation) and polysaccharide production. Therefore, we were interested in visualizing the in situ characteristics of P. aeruginosa within the sputum of CF patients. A tissue clearing technique was applied to sputum samples after embedding the samples into a hydrogel matrix to retain the 3D structures relative to host cells. After tissue clearing, fluorescent labels and dyes were added to allow visualization. Fluorescence in situ hybridization was performed for the visualization of bacterial cells, binding of fluorescently labeled anti-Psl-antibodies for the visualization of the exopolysaccharide and DAPI staining to stain host cells to obtain structural insight. These methods allowed for the high-resolution imaging of P. aeruginosa within the sputum of CF patients via confocal laser scanning microscopy.

Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients

This protocol provides methods for visualization of bacterial cells and polysaccharide synthesis locus (Psl) polysaccharide within the sputum of cystic fibrosis patients.

Early detection and eradication of Pseudomonas aeruginosa within the lungs of cystic fibrosis patients can reduce the chance of developing chronic ...

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a poor correlation between antibiotic susceptibility testing (AST) results using standard diagnostic methods (e.g., broth microdilution, disk diffusion, or Etest) and clinical outcomes after antibiotic treatment. Attempts to improve AST by the use of off-the-shelf biofilm growth platforms show little improvement in results. The limited ability of in vitro biofilm systems to mimic the physicochemical environment of the CF lung and, therefore bacterial physiology and biofilm architecture, also acts as a brake on the discovery of novel therapies for CF infection. Here, we present a protocol to perform AST of CF pathogens grown as mature, in vivo-like biofilms in an ex vivo CF lung model comprised of pig bronchiolar tissue and synthetic CF sputum (ex vivo&#160;pig lung, EVPL).
Several in vitro&#160;assays exist for biofilm susceptibility testing, using either standard laboratory medium or various formulations of synthetic CF sputum in microtiter plates. Both growth medium and biofilm substrate (polystyrene plate vs. bronchiolar tissue) are likely to affect biofilm antibiotic tolerance. We show enhanced tolerance of clinical Pseudomonas aeruginosa and Staphylococcus aureus isolates in the ex vivo model; the effects of antibiotic treatment of biofilms is not correlated with the minimum inhibitory concentration (MIC) in standard microdilution assays or a sensitive/resistant classification in disk diffusion assays.
The ex vivo platform could be used for bespoke biofilm AST of patient samples and as an enhanced testing platform for potential antibiofilm agents during pharmaceutical research and development. Improving the prescription or acceleration of antibiofilm drug discovery through the use of more in vivo-like testing platforms could drastically improve health outcomes for individuals with CF, as well as reduce the costs of clinical treatment and discovery research.

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

This workflow can be used to perform antibiotic susceptibility testing using an established&#160;ex vivo model of bacterial biofilm in the lungs of individuals with cystic fibrosis. Use of this model could enhance the clinical validity of MBEC (minimal biofilm eradication concentration) assays.

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a ...

Tools for the Real-Time Assessment of a Pseudomonas aeruginosa Infection Model

Pseudomonas aeruginosa (Pa) is one of the most common opportunistic pathogens associated with cystic fibrosis (CF). Once Pa colonization is established, a large proportion of the infecting bacteria form biofilms within airway sputum. Pa biofilms isolated from CF sputum have been shown to grow in small, dense aggregates of ~10-1,000 cells that are spatially organized and exhibit clinically relevant phenotypes such as antimicrobial tolerance. One of the biggest challenges to studying how Pa aggregates respond to the changing sputum environment is the lack of nutritionally relevant and robust systems that promote aggregate formation. Using a synthetic CF sputum medium (SCFM2), the life history of Pa aggregates can be observed using confocal laser scanning microscopy (CLSM) and image analysis at the resolution of a single cell. This in vitro system allows the observation of thousands of aggregates of varying size in real time, three dimensions, and at the micron scale. At the individual and population levels, having the ability to group aggregates by phenotype and position facilitates the observation of aggregates at different developmental stages and their response to changes in the microenvironment, such as antibiotic treatment, to be differentiated with precision.

Tools for the Real-Time Assessment of a Pseudomonas aeruginosa Infection Model

Synthetic cystic fibrosis sputum medium (SCFM2) can be utilized in combination with both confocal laser scanning microscopy and fluorescence-activated cell sorting to observe bacterial aggregates at high resolution. This paper details methods to assess aggregate populations during antimicrobial treatment as a platform for future studies.

Pseudomonas aeruginosa (Pa) is one of the most common opportunistic pathogens associated with cystic fibrosis (CF). Once Pa colonization is established, a ...