Name: in vivo mouse model of spinal implant infection
Uploaded: 2020-06-23T12:30:00
Description: Watch this Scientific Journal Video about In Vivo Mouse Model of Spinal Implant Infection at JoVE.com

The authors would like to acknowledge the receipt of both the Pediatric Orthopaedic Society of North America Biomet Spine Grant and the National Institutes of Health Clinical and Translational Science Institute KL2 Grant, and the HH Lee Surgical Research Grant as major funding sources for these experiments.

All animals were handled in strict accordance with good animal practice as defined in the federal regulations as set forth in the Animal Welfare Act (AWA), the 1996 Guide for the Care and Use of Laboratory Animals, PHS Policy for the Humane Care and Use of Laboratory Animals, as well as the institution&#8217;s policies and procedures as set forth in the Animal Care and Use Training Manual, and all animal work was approved by the University of California Los Angeles Chancellor&#8217;s Animal Research Committee (ARC).
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<ol>
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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=Rates+of+infection+after+spine+surgery+based+on+108,419+procedures:+a+report+from+the+Scoliosis+Research+Society+Morbidity+and+Mortality+Committee.">Rates of infection after spine surgery based on 108,419 procedures: a report from the Scoliosis Research Society Morbidity and Mortality Committee.</a> Spine. 36 (7), 556-563 (2011).</li><li>Abbey, D. M., Turner, D. M., Warson, J. S., Wirt, T. C., Scalley, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatment+of+postoperative+wound+infections+following+spinal+fusion+with+instrumentation.">Treatment of postoperative wound infections following spinal fusion with instrumentation.</a> Journal of Spinal Disorders. 8 (4), 278-283 (1995).</li><li>Silber, J. 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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=Risk+factors+for+surgical+site+infection+in+spinal+surgery.">Risk factors for surgical site infection in spinal surgery.</a> Journal of Neurosurgery. 98, 149-155 (2003).</li><li>Ofluoglu, E. 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=Implant-related+infection+model+in+rat+spine.">Implant-related infection model in rat spine.</a> Archives of Orthopaedic and Trauma Surgery. 127 (5), 391-396 (2007).</li><li>Guiboux, J. 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=The+role+of+prophylactic+antibiotics+in+spinal+instrumentation.+A+rabbit+model.">The role of prophylactic antibiotics in spinal instrumentation. A rabbit model.</a> Spine. 23 (6), 653-656 (1998).</li><li>Stavrakis, A. I., 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=Current+Animal+Models+of+Postoperative+Spine+Infection+and+Potential+Future+Advances.">Current Animal Models of Postoperative Spine Infection and Potential Future Advances.</a> Frontiers in Medicine (Lausanne). 2, 34 (2015).</li><li>Pribaz, J. R., 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=Mouse+model+of+chronic+post-arthroplasty+infection:+noninvasive+in+vivo+bioluminescence+imaging+to+monitor+bacterial+burden+for+long-term+study.">Mouse model of chronic post-arthroplasty infection: noninvasive in vivo bioluminescence imaging to monitor bacterial burden for long-term study.</a> Journal of Orthopaedic Research. 30 (3), 335-340 (2012).</li><li>Bernthal, N. 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=A+mouse+model+of+post-arthroplasty+Staphylococcus+aureus+joint+infection+to+evaluate+in+vivo+the+efficacy+of+antimicrobial+implant+coatings.">A mouse model of post-arthroplasty Staphylococcus aureus joint infection to evaluate in vivo the efficacy of antimicrobial implant coatings.</a> PLoS One. 5 (9), 12580 (2010).</li><li>Niska, J. 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=Monitoring+bacterial+burden,+inflammation+and+bone+damage+longitudinally+using+optical+and+muCT+imaging+in+an+orthopaedic+implant+infection+in+mice.">Monitoring bacterial burden, inflammation and bone damage longitudinally using optical and muCT imaging in an orthopaedic implant infection in mice.</a> PLoS One. 7 (10), 47397 (2012).</li><li>Francis, K. 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=Monitoring+bioluminescent+Staphylococcus+aureus+infections+in+living+mice+using+a+novel+luxABCDE+construct.">Monitoring bioluminescent Staphylococcus aureus infections in living mice using a novel luxABCDE construct.</a> Infection and Immunity. 68 (6), 3594-3600 (2000).</li><li>Dworsky, E. 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=Novel+in+vivo+mouse+model+of+implant+related+spine+infection.">Novel in vivo mouse model of implant related spine infection.</a> Journal of Orthopaedic Research. 35 (1), 193-199 (2017).</li><li>Hegde, S. 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=Activity+of+telavancin+against+heterogeneous+vancomycin-intermediate+Staphylococcus+aureus+(hVISA)+in+vitro+and+in+an+in+vivo+mouse+model+of+bacteraemia.">Activity of telavancin against heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) in vitro and in an in vivo mouse model of bacteraemia.</a> Journal of Antimicrobial Chemotherapy. 65 (4), 725-728 (2010).</li><li>Crandon, J. L., Kuti, J. L., Nicolau, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+efficacies+of+human+simulated+exposures+of+telavancin+and+vancomycin+against+methicillin-resistant+Staphylococcus+aureus+with+a+range+of+vancomycin+MICs+in+a+murine+pneumonia+model.">Comparative efficacies of human simulated exposures of telavancin and vancomycin against methicillin-resistant Staphylococcus aureus with a range of vancomycin MICs in a murine pneumonia model.</a> Antimicrobial Agents and Chemotherapy. 54 (12), 5115-5119 (2010).</li><li>Reyes, N., 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=Efficacy+of+telavancin+in+a+murine+model+of+bacteraemia+induced+by+methicillin-resistant+Staphylococcus+aureus.">Efficacy of telavancin in a murine model of bacteraemia induced by methicillin-resistant Staphylococcus aureus.</a> Journal of Antimicrobial Chemotherapy. 58 (2), 462-465 (2006).</li><li>Sakoulas, G., Eliopoulos, G. 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Implant related infections in the spine portend poor outcomes for patients1,2,3,4,5. Unlike many other areas in the body, infected hardware in the spine frequently cannot be removed due to the risk of instability and neurologic compromise. This unique challenge in the setting of biofilm bacteria resistant to systemic antibiotic therapy necessitate novel approa...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/60560">In vivo Mouse Model of Spinal Implant Infection</a>. The Authors section was updated from:
Benjamin V. Kelley1 
Stephen D. Zoller1 
Danielle Greig1 
Kellyn Hori1 
Nicolas Cevallos1 
Chad Ishmael1 
Peter Hsiue1 
Rishi Trikha1 
Troy Sekimura2 
Thomas Olson2 
Ameen Chaudry2 
Michael M. Le2 
Anthony A. Scaduto1 
Kevin P. Francis1 
Nicholas M. Bernthal1 
1Department of Orthopaedic Surgery, University of California Los Angeles 
2David Geffen School of Medicine, University of California Los Angeles
to:
Benjamin V. Kelley1 
Christopher Hamad1 
Stephen D. Zoller1 
Danielle Greig1 
Zeinab Mamouei1 
Rene Chun1 
Kellyn Hori1 
Nicolas Cevallos1 
Chad Ishmael1 
Peter Hsiue1 
Rishi Trikha1 
Troy Sekimura2 
Brandon Gettleman3 
Autreen Golzar2 
Adrian Lin2 
Thomas Olson2 
Ameen Chaudry2 
Michael M. Le2 
Anthony A. Scaduto1 
Kevin P. Francis1 
Nicholas M. Bernthal1 
1Department of Orthopaedic Surgery, University of California Los Angeles 
2David Geffen School of Medicine, University of California Los Angeles 
3University of South Carolina School of Medicine, University of South Carolina

An erratum was issued for:&#160;<a href="https://www.jove.com/t/60560">In vivo Mouse Model of Spinal Implant Infection</a>. The Authors section was updated.

Erratum: In vivo Mouse Model of Spinal Implant Infection

The purpose of this method is to describe a novel mouse model of spinal implant infection (SII). This model was designed to provide an inexpensive and accurate tool to flexibly assess the effect of host, pathogen, and/or implant variables in vivo. Testing potential therapeutics and treatment strategies for spinal implant infections in this model is aimed at guiding research development prior to application in larger animal models and clinical trials.
Implant related infection after spine surgery is a devastating complication and unfortunately occurs in approximately 3&#8211;8% of patients undergoing elective spine surgery1,2,3,4,5 and up to 65% of patients undergoing multilevel or revision surgery6. Treatment of spinal implant infections often requires multiple hospitalizations, multiple surgeries, and prolonged antibiotic therapy. SIIs portend poor patient outcomes including neurological compromise, disability, and an increased risk of mortality. Management of SII is extremely expensive, costing upwards of $900,000 per patient7.
Staphylococcus aureus is the most common virulent pathogen of SII8,9,10,11. Bacteria can seed the hardware directly during surgery, through the wound during the postoperative period, or later via hematogenous spread. In the presence of metal implants, S. aureus form biofilm that protects the bacteria from antibiotic therapy and immune cells. While removal of infected hardware may help effectively eradicate an infection, this is frequently not feasible in the spine without causing destabilization and risking neurologic compromise12.
In the absence of explanting infected hardware, novel approaches are needed to prevent, detect, and treat SII. Historically, there have been limited animal models of SII to efficiently assess the safety and efficacy of novel therapies. Previous animal models of SII require large numbers of animals and collection of data points requiring euthanasia including colony counting, histology, and culture13,14,15. Lacking longitudinal in vivo monitoring, these models only provide one data point per animal and are therefore expensive and inefficient.
Previous work studying a mouse model of knee arthroplasty infection established the value and accuracy of noninvasive in vivo optical imaging to longitudinally monitor infection burden16. The detection of bioluminescence allows bacterial burden to be quantified over a longitudinal time course in a single animal humanely, accurately, and efficiently. Moreover, prior studies have demonstrated a high correlation between in vivo bioluminescence and CFUs adherent to implants17. The capacity to track infection over time, has led to a more nuanced understanding of implant related infection. In addition, monitoring longitudinal infection in this way, has allowed the effectiveness of antibiotic therapy and novel antimicrobials to be accurately assessed16,17,18.
Leveraging these tools, we developed and validated a model of postoperative spinal implant infection. In the method presented, we utilize an inoculum of bioluminescent S. aureus Xen36 to establish an in vivo mouse model of SII to longitudinally monitor bacterial burden16,17,18. This novel model provides a valuable tool to efficiently test potential detection, prevention, and treatment strategies for SII prior to their application in larger animal models and clinical trials.

<table>
	<tbody>
		<tr>
			<td>Analytical Balance ME104</td>
			<td>Mettler Toledo</td>
			<td>30029067</td>
			<td>120 g capacity, 0.1 mg readability, backlit LCD, internal adjustment, metal base</td>
		</tr>
		<tr>
			<td>BD Bacto Tryptic Soy Broth</td>
			<td>Becton Dickinson (BD)</td>
			<td>BD 211825</td>
			<td>BD Bacto Tryptic Soy Broth (Soybean-Casein Digest Medium)</td>
		</tr>
		<tr>
			<td>Biomate 3S UV-VIS Spectrophotometer</td>
			<td>Thermo Scientific</td>
			<td>840-208300</td>
			<td>Spectrophotometer; Thermo Scientific; BioMate 3S; Six-position cell holder; Spectral bandwidth: 1.8nm; Long-life xenon lamp; Store up to 40 test methods; 16L x 13W x 9 in. H; 19 lb.; 100/240V US line cord</td>
		</tr>
		<tr>
			<td>Bioshield 720+ swinging bucket rotor</td>
			<td>Thermo Scientific</td>
			<td>75003183</td>
			<td>Rotor, Swinging bucket; Thermo Scientific; BIOShield 720 high speed; Capacity: 4 x 180mL (0.72L); Angle: 90 deg. ; Max. speed/RCF: 6300rpm/7188 x g; Max. radius: 16.2cm</td>
		</tr>
		<tr>
			<td>Branson Ultrasonics 2510R-MTH (Sonicator)</td>
			<td>Branson Ultrasonics</td>
			<td>CPX952217R</td>
			<td>*similar model, our model is discontinued* Branson Ultrasonics MH Series Heated Ultrasonic Cleaning Bath, 120V, 0.75 gal</td>
		</tr>
		<tr>
			<td>Bullet Blender Storm Homogenizer</td>
			<td>Next Advance</td>
			<td>BBY24M</td>
			<td>The Bullet Blender Storm is the most powerful member of the Bullet Blender family. Homogenize up to 24 of your toughest samples (mouse femur, skin, cartilage, tumor, etc.) in just minutes. Air cooling&#8482; minimizes sample heat up. Uses 1.5ml screw-cap RINO&#174; tubes or snap-cap Eppendorf&#174; Safe-lock&#8482; tubes.</td>
		</tr>
		<tr>
			<td>Germinator 500</td>
			<td>Electron Microscopy Sciences</td>
			<td>66118-10</td>
			<td>The Germinator 500 is designed to decontaminate metal micro-dissecting instruments only. It is to be 
			used exclusively for research purposes. The Germinator 500 should not be used as a substitute for 
			traditional methods of terminal sterilization. Effective sterilization cannot be assured due to lack of routine 
			sterilization-efficacy monitoring methods for glass bead sterilization. The Germinator 500 has been 
			designed and built to pass the Validation of Dry Sterilizer Spore Suspension Test: USP XXIII, Part 1211.</td>
		</tr>
		<tr>
			<td>Heracell 150i CO2 Incubator</td>
			<td>Thermo Scientific</td>
			<td>51026282</td>
			<td>Single 150L</td>
		</tr>
		<tr>
			<td>IVIS Lumina X5 Imaging System</td>
			<td>Perkin Elmer</td>
			<td>CLS148590</td>
			<td>The IVIS Lumina X5 high-throughput 2D optical imaging system combines high-sensitivity bioluminescence and fluorescence with high-resolution x-ray into a compact system that fits on your benchtop. With an expanded 5 mouse field of view for 2D optical imaging plus our unique line of accessories to accelerate setup and labeling, it has never been easier or faster to get robust data&#8212;and answers&#8212;on anatomical and molecular aspects of disease.</td>
		</tr>
		<tr>
			<td>MAXQ 4450 Digtial Incubating Bench Shaker</td>
			<td>Thermo Scientific</td>
			<td>SHKE4450</td>
			<td>Shaker, Incubated; Thermo Scientific; Digital; MaxQ 4450; Speed 15 to 500rpm +/-1rpm; 5 deg. C above ambient to 80 deg. C; 120V 50/60Hz</td>
		</tr>
		<tr>
			<td>PBS, Phosphate Buffered Saline</td>
			<td>Fisher Bioreagents</td>
			<td>BP24384</td>
			<td>PBS, Phosphate Buffered Saline, 1X Solution, pH 7.4</td>
		</tr>
		<tr>
			<td>Sorvall Legend Micro 21 Centrifuge, Ventilated</td>
			<td>Thermo Scientific</td>
			<td>75002436</td>
			<td>24 x 1.5/2.0mL rotor with ClickSeal biocontainment lid</td>
		</tr>
		<tr>
			<td>SORVALL LEGEND X1R 120V Centrifuge</td>
			<td>Thermo Scientific</td>
			<td>75004261</td>
			<td>Centrifuge, Benchtop; Thermo Scientific; Sorvall Legend X1R (Refrigerated), 1L capacity; Max. Speed/RCF 15,200rpm/25,830 x g; CFC-free cooling -10C to +40C; 120V 60Hz</td>
		</tr>
		<tr>
			<td>Staphylococcus aureus - Xen36</td>
			<td>Perkin Elmer</td>
			<td>119243</td>
			<td>Staphylococcus aureus - Xen36 bioluminescent pathogenic bacteria for in vivo and in vitro drug discovery. This product was derived from a parental strain from the American Type Culture Collection, used under license. Staph. aureus-Xen36 possesses a stable copy of the Photorhabdus luminescens lux operon on the native plasmid.</td>
		</tr>
		<tr>
			<td>TUTTNAUER AUTOCLAVE 2540E 120V</td>
			<td>Heidolph Tuttnauer</td>
			<td>23210401</td>
			<td>Sterilizer, Benchtop; Heidolph; Tuttnauer; Model 2540E; Self-contained design with refillable reservoir controls water purity for sterilization; 120V 50/60Hz; 1400w. With electronic controls</td>
		</tr>
		<tr>
			<td>Tween 80</td>
			<td>Fisher Bioreagents</td>
			<td>BP338-500</td>
			<td>Tween 80, Fisher BioReagents, Non-ionic detergent for selective protein extraction</td>
		</tr>
		<tr>
			<td>Vortex mixer VX-200</td>
			<td>Labnet Internation</td>
			<td>S0200</td>
			<td>120V touch or continuous mixer, 230V: 0 - 2,850 rpm,120V: 0 - 3,400 rpm</td>
		</tr>
		<tr>
			<td>0.9% Sodium Chloride</td>
			<td>Pfizer Injectables/Hospira</td>
			<td>00409-4888-10</td>
			<td>0.9% Sodium Chloride Injection, USP</td>
		</tr>
	</tbody>
</table>

in vivo mouse model of spinal implant infection

Spine implant infections portend poor outcomes as diagnosis is challenging and surgical eradication is at odds with mechanical spinal stability. The purpose of this method is to describe a novel mouse model of spinal implant infection (SII) that was created to provide an inexpensive, rapid, and accurate in vivo tool to test potential therapeutics and treatment strategies for spinal implant infections.
In this method, we present a model of posterior-approach spinal surgery in which a stainless-steel k-wire is transfixed into the L4 spinous process of 12-week old C57BL/6J wild-type mice and inoculated with 1 x 103 CFU of a bioluminescent strain of Staphylococcus aureus Xen36 bacteria. Mice are then longitudinally imaged for bioluminescence in vivo on post-operative days 0, 1, 3, 5, 7, 10, 14, 18, 21, 25, 28, and 35. Bioluminescence imaging (BLI) signals from a standardized field of view are quantified to measure in vivo bacterial burden.
To quantify bacteria adhering to implants and peri-implant tissue, mice are euthanized and the implant and surrounding soft tissue are harvested. Bacteria are detached from the implant by sonication, cultured overnight and then colony forming units (CFUs) are counted. The results acquired from this method include longitudinal bacterial counts as measured by in vivo S. aureus bioluminescence (mean maximum flux) and CFU counts following euthanasia.
While prior animal models of instrumented spine infection have involved invasive, ex vivo tissue analysis, the mouse model of SII presented in this paper leverages noninvasive, real time in vivo optical imaging of bioluminescent bacteria to replace static tissue study. Applications of the model are broad and may include utilizing alternative bioluminescent bacterial strains, incorporating other types of genetically engineered mice to contemporaneously study host immune response, and evaluating current or investigating new diagnostic and therapeutic modalities such as antibiotics or implant coatings.

The procedure presented here was used to assess the efficacy of antibiotic regimens in an in vivo mouse model of SII. Specifically, the efficacy of combination vancomycin and rifampin antibiotic therapy was compared to vancomycin monotherapy and untreated infected controls.
Prior to surgery, mice were randomized to either combination therapy, monotherapy, or infected control. A statistical power analysis was performed to calculate sample size. Anticipated means of mean maximum flux 1 x 10...

Watch this Scientific Journal Video about In Vivo Mouse Model of Spinal Implant Infection at JoVE.com

In Vivo Mouse Model of Spinal Implant Infection

The protocol describes a novel in vivo mouse model of spinal implant infection where a stainless-steel k-wire implant is infected with bioluminescent Staphylococcus aureus Xen36. Bacterial burden is monitored longitudinally with bioluminescent imaging and confirmed with colony forming unit counts after euthanasia.

Spine implant infections portend poor outcomes as diagnosis is challenging and surgical eradication is at odds with mechanical spinal stability. The ...

Postoperative infection is a devastating complication of spinal surgery. This mouse model of spinal implant infection allows researchers to study the effect of host, implant, and therapeutic factors on infection. This technique quantifies real-time longitudinal bacterial burden, humanely and efficiently, in-vivo.Using a frozen stock of S.aureus zen 36, streak the bacteria onto Luria broth plates containing 200 micrograms per milliliter of kanamycin and incubate for 12 to 16 hours at 37 degrees Celsius. At the end of the incubation, individually culture single colonies from the S.aureus zen 36 culture in tryptic soy broth containing 200 micrograms per milliliter kanamycin for 12 to 16 hours at 37 degrees Celsius and 200 revolutions per minute. The next day, dilute the culture in fresh broth at a one to 50 ratio and culture the bacteria for an additional two hours to allow the isolation of mid-logarithmic phase bacteria.At the end of the incubation, pellet the bacterial cells by centrifugation and wash the cells three times in one milliliter of fresh PBS per wash. After the last wash, measure the absorbance at 600 nanometers. The ideal optical density is 0.750.Then, re-suspend the bacteria at a one times 10 to the third colony forming units per two microliters of PBS concentration. Use clippers to remove hair from the sacrum and upper thoracic spine of the 12 week old male C-57 black six mouse. Deliver pain medicine via subcutaneous injection immediately before skin preparation and repeat in three days.Sterilize the surgical site using three alternating Betadine and alcohol wipes. After the third wipe, place the mouse in the prone position on a sterile surgical bed and maximally flex the hips. Before making an incision, confirm a lack of response to toe pinch.Palpate for the iliac crest to approximately the lumbar four vertebrae body and use a number 15 surgical scalpel blade to make a longitudinal, two centimeter skin incision. Palpate the spinous process to confirm the midline and continue the incision down to the bone. Dissect sub-periosteally on the right side of the L-4 spinous process, extending laterally to the transverse process, and pass an open absorbable braided suture size 5.0 cephalad and caudad to the L-4 body through the fascia.Using a 25-gauge spinal needle, ream the spinous process of L-4 and insert a 0.1 millimeter diameter, one centimeter long, L-shaped surgical grade stainless steel implant along the lamina, with the long arm laying cephalad. Inoculate the implant with one times 10 to the third colony forming units per two microliters of bioluminescent S.aureus zen 36, taking care to ensure that all of the solution contacts the implant. Immediately tie the suture to ensure containment of the inoculum to the implant, and use a second absorbable suture to close the skin in a running fashion.Place the mouse on a heating pad with monitoring until full recovery. Obtain postoperative radiographs to confirm the appropriate placement of the implant. To measure the bacterial burden, on the appropriate day post-infection, use clippers to remove any regrown hair from the sacrum to the upper thoracic spine and place the mouse onto a bioluminescent imaging platform.Using large bending settings with a 13 centimeter field of view, capture the bioluminescent signal for five minutes. Then, use bioluminescent imaging software to isolate a standard ovoid region of interest to quantify the mean and maximum total flux of the bioluminescence. At the appropriate experimental endpoint, after preparing the mouse as demonstrated for the surgical procedure, use a number 15 scalpel blade to sharply incise the old incision and use sterile scissors to bluntly dissect to the L-4 spinous process.When the implant can be identified, use a needle driver to gently twist and remove the implant from its position, and use sterile forceps and scissors to harvest approximately one gram of spinous process bone and soft tissue immediately surrounding the surgical implant. Place the tissue in one milliliter of PBS in a pre-weighed small conical rhino tube containing four sharp homogenizing beads and place the implant in 250 microliters of 0.3%TWEEN 80 in triptych soy broth. Weigh the tube of tissue and use a homogenizer to homogenize the sample.Vortex the implants at medium strength for two minutes, then sonicate them for 10 minutes. Dilute the implant in tissue samples one to 10, one to 101, one to 1000, and plate them on triptych soy broth plates containing 1%agar. Place the plates in an incubator at 37 degrees Celsius overnight.The following day, count the colony forming units from the implant and surrounding tissue cultures. Infected control mice demonstrate BLI signals that peak on post-infection day 10 and remain above one times 10 to the fifth photons per second per square centimeter per teridian until sacrifice, successfully modeling a chronic spinal implant infection. Mice treated with vancomycin monotherapy exhibit a significantly lower BLI signal compared to infected controls, with a two-fold reduction from post infections day 10 through 21.After post-infection day 21, there is no significant difference in BLI between the monotherapy and infected control groups. Mice treated with vancomycin-rifampin combination therapy have an even lower BLI signal that is 20 fold lower than infected controls on post-infection day 10. This significant reduction persists until post infection day 28, after which no significant difference in BLI is observed between any of the groups.Implants and surrounding tissue harvested and processed on day 35 revealed no significant differences in colony-forming units between infected control, monotherapy, and combination therapy groups. Following this procedure, the host immune response may also be studied such as by utilizing mice with fluorescently-labeled neutrophils. The development of this efficient mouse model has allowed us to identify effective novel treatments for spinal implant infection.

Research

JoVE Journal

Medicine

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