Name: come to the light side: in vivo monitoring of pseudomonas aeruginosa biofilm infections in chronic wounds in a diabetic hairless murine model
Uploaded: 2017-10-10T13:00:00
Description: Watch this Scientific Journal Video about Come to the Light Side: In Vivo Monitoring of Pseudomonas aeruginosa Biofilm Infections in Chronic Wounds in a Diabetic Hairless Murine Model at JoVE.com

The authors would like to thank the American Diabetes Association for supporting this work (Grant # #7-13-BS-180), the Michigan State University Research Technology Support Facility for providing training and access to the in vivo imaging system and the Michigan State University Investigative Histopathology Lab for processing the mouse biopsies for histopathological examination.

Animal experiments were approved by the Institutional Animal Care and Use Committee of Michigan State University.
1. Preparation of Occlusive Dressings and Silicone Spacers
<ol>
	<li>Cut the transparent occlusive dressing to make squares approximately 1 cm x 1 cm with scissors.</li>
	<li>Cut 10 mm circles on a 0.5 mm thick silicone sheet using a 10 mm biopsy punch.&#160;Center a 5 mm biopsy punch in the middle of the 10 mm circle and press firmly to create a hole to form a &#34;donut&#34;-li...

<ol>
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Here we describe a new mouse model for the study of biofilms in diabetic chronic wounds that has many advantages to create a reproducible, translatable, and flexible model.
The first innovation is the use of hairless mice. Other mouse models have been developed to study diabetic chronic wound healing10,11, but all have relied on the use of haired mice requiring the removal of fur by processes that involve either waxing or hair clipping...

Biofilms are complex communities of microorganisms embedded in a matrix of polymeric substances that have been highlighted as a contributing factor for the poor resolution of chronic wounds1. The study of these highly organized, persistent microbial populations is particularly important for diabetic patients where poor circulation on the limbs and altered peripheral sensory mechanisms lead to undetected lesions2. In the United States, it is estimated that 15% of diabetic patients will develop at least one ulcer during the course of their lives. This translates to an economic expenditure of around 28 billion dollars in treatment3,4, not to mention the immensurable emotional and social burden. Understanding the factors that allow microbial communities to persist in the wound bed and the impact these biofilms have in the healing events is imperative to drive better care for affected patients and propel the development of new treatment approaches. Therefore, the establishment of reproducible and translatable in vivo models for exploring bacterial-host interactions is paramount.
Murine models have been successfully developed to study the impact of biofilms in chronic wounds. These models, however, often utilize haired species and evaluate biofilm clearance by plate counts for viable bacterial cells of excised tissue from sacrificed animals, making them time consuming and costly.
A biophotonic alternative to the end point sampling of animals in evaluating infection was first proposed by Contag et al. (1995)5, who developed a method to capture luminescence from constitutively bioluminescent Salmonella typhimurium to measure antibiotic treatment efficacy. Other studies taking advantage of bioluminescence-emitting bacteria followed. For example, Rochetta et al. (2001)6 validated an infection model to study Escherichia coli thigh infections in mice by measuring luminescence using an intensified charge-coupled device and later, Kadurugamuwa et al. (2003)7 took advantage of the photon emitting properties of an engineered strain of Staphylococcus aureus to investigate the efficacy of several antibiotics in a catheter wound model in mice.
The method characterized here presents a straightforward protocol to induce diabetes in hairless mice, produce and inoculate wounds with pre-formed bioluminescent biofilms of P. aeruginosa, and conduct biophotonic monitoring of the infection using an in vivo imaging system. It offers a direct, rapid, in situ, non-invasive and quantitative process to evaluate biofilms in chronic wounds and in addition, allows for additional analysis such as microscopic imaging of the healing wounds, intermittent blood collection for cytokine measurements, and terminal tissue collection for histology.

<table>
	<tbody>
		<tr>
			<td>Opsite</td>
			<td>Smith &#38; Nephew</td>
			<td>Model 66000041</td>
			<td>Smith &#38; Nephew Flexfix Opsite Transparent Adhesive Film Roll 4&#34; x 11yards</td>
		</tr>
		<tr>
			<td>SKH-1 mice Crl:SKH1-Hrhr</td>
			<td>Charles River Breeding Laboratories</td>
			<td>SKH1</td>
			<td>Hairless mice, 8 weeks old</td>
		</tr>
		<tr>
			<td>Streptozotocin (STZ)</td>
			<td>Sigma Aldrich</td>
			<td>S0130-1G</td>
			<td>Streptozocin powder, 1g</td>
		</tr>
		<tr>
			<td>AccuChek glucometer</td>
			<td>Accu-Chek Roche</td>
			<td>Art No. 05046025001</td>
			<td>ACCU-CHEK CompactPlus Diabetes Monitoring Care Kit</td>
		</tr>
		<tr>
			<td>Pseudomonas aeruginosa Xen 41</td>
			<td>Perkin Elmer</td>
			<td>119229</td>
			<td>Bioluminescent Pseudomonas aeruginosa</td>
		</tr>
		<tr>
			<td>Polycarbonate membrane filters</td>
			<td>Sigma Aldrich</td>
			<td>P9199</td>
			<td>Millipore polycarbonate membrane filters with 0.2 &#956;m pore size</td>
		</tr>
		<tr>
			<td>Dulbelcco phosphate buffer saline (DPBS)</td>
			<td>Sigma Aldrich</td>
			<td>D8537</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td>Tryptic soy agar</td>
			<td>Sigma Aldrich</td>
			<td>22091</td>
			<td>Culture agar</td>
		</tr>
		<tr>
			<td>Meloxicam</td>
			<td>Henry Schein Animal Health</td>
			<td>49755</td>
			<td>Eloxiject (Meloxicam) 5mg/mL, solution for injection</td>
		</tr>
		<tr>
			<td>10% povidone-iodine (Betadine)</td>
			<td>Purdue Products LP</td>
			<td>301879-OA</td>
			<td>Swabstick, Betadine Solution. Antiseptic. Individ. Wrapped, 200/case</td>
		</tr>
		<tr>
			<td>4% paraformaldehyde</td>
			<td>Fisher Scientific</td>
			<td>AAJ61899AK</td>
			<td>Alfa Aesar Paraformaldehyde, 4% in PBS</td>
		</tr>
		<tr>
			<td>Capillary glass tube</td>
			<td>Fisher Scientific</td>
			<td>22-362-566</td>
			<td>Heparinized Micro-Hematocrit Capillary Tubes</td>
		</tr>
		<tr>
			<td>Silicone to make splints</td>
			<td>Invitrogen Life Technologies Corp</td>
			<td>P-18178</td>
			<td>Press-to-Seal Silicone Sheet, 13cm x 18cm, 0.5mm thick, set of 5 sheets</td>
		</tr>
		<tr>
			<td>Tryptic soy broth</td>
			<td>Sigma Aldrich</td>
			<td>22092</td>
			<td>Culture broth</td>
		</tr>
		<tr>
			<td>IVIS Spectrum</td>
			<td>Perkin Elmer</td>
			<td>124262</td>
			<td>In vivo imaging system</td>
		</tr>
		<tr>
			<td>IVIS Spectrum Isolation chamber</td>
			<td>Perkin Elmer</td>
			<td>123997</td>
			<td>XIC-3 animal isolation chamber</td>
		</tr>
		<tr>
			<td>HEPA filter</td>
			<td>Teleflex</td>
			<td>28022</td>
			<td>Gibeck ISO-Gard HEPA Light number 28022</td>
		</tr>
		<tr>
			<td>Biopsy punches</td>
			<td>VWR International Inc</td>
			<td>21909-142</td>
			<td>Disposable Biopsy Punch, 5mm, Sterile, pack of 50.</td>
		</tr>
		<tr>
			<td>Biopsy punches</td>
			<td>VWR International Inc</td>
			<td>21909-140</td>
			<td>Disposable Biopsy Punch, 4mm, Sterile, pack of 50.</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>J.T.Baker</td>
			<td>1916-01</td>
			<td>Dextrose, Anhydrous, Powder</td>
		</tr>
		<tr>
			<td>Citric acid</td>
			<td>Sigma Aldrich</td>
			<td>C2404-100G</td>
			<td>Citric Acid</td>
		</tr>
		<tr>
			<td>Mastisol</td>
			<td>Eloquest Healthcare</td>
			<td>HRI 0496-0523-48</td>
			<td>Mastisol Medical Liquid Adhesive 2/3 mL vial, box of 48</td>
		</tr>
		<tr>
			<td>Corning 96-well black plates</td>
			<td>Fisher Scientific</td>
			<td>07-200-567</td>
			<td>96-well clear bottom black polysterene microplates</td>
		</tr>
		<tr>
			<td>25 gauge 5/8 inch needle</td>
			<td>BD</td>
			<td>305122</td>
			<td>Regular bevel needle</td>
		</tr>
		<tr>
			<td>Bransonic M Ultrasonic Cleaning Bath</td>
			<td>Branson Ultrasonics</td>
			<td>N/A</td>
			<td>Ultrasonic Cleaner</td>
		</tr>
	</tbody>
</table>

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.

In developing this new model, we observed many advantages in utilizing hairless SKH-1 over C57BL/6J mice, which we have used in the past. Animals subjected to STZ injections normally experience gradual weight loss with the onset of diabetes; however, in wound healing experiments previously conducted by our laboratories reproducing the model presented by Dunn et al. (2012)9 using C57BL/6J, drastic weight loss was observed (Figure 1</str...

Watch this Scientific Journal Video about Come to the Light Side: In Vivo Monitoring of Pseudomonas aeruginosa Biofilm Infections in Chronic Wounds in a Diabetic Hairless Murine Model at JoVE.com

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.

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. ...

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