This work was supported by a Burroughs-Wellcome Career Award and by National Institutes of Health grant AI074832 to G. Y. Liu.

1. Preparing the MRSA for Infection (two Days Prior to Infection)
<ol>
<li>Inoculate a loopful of MRSA from a stock culture to a blood agar (Trypticase Soy Agar (TSA)) plate.</li>
<li>Check the hemolysis phenotype (a clear zone around each colony) on the blood agar plate.</li>
<li>Pick a colony that has a hemolytic phenotype that is consistent with other experiments.</li>
<li>Inoculate the colony into 3 mL Todd Hewitt Broth (THB),with the appropriated antibiotic when necessary, in a 15 mL snap-capped tube.</li>
<li>Incubate at 37&deg;C overnight with shaking at 220 rpm.</li>
</ol>
2. Preparing the Mice for Infection (one Day Prior to Infection)
<ol>
<li>Depending on the size of the mice, shave the fur off a 3 x 4 cm area on the back of mice.</li>
<li>Apply ~5 mm3 hair remover cream (purchased from a local drug store) to the shaved area.</li>
<li>Allow the hair remover cream to incubate on the skin surface for approximately 1 min.</li>
<li>Wet paper towels with ddH2O.</li>
<li>Wipe off the hair remover cream with the wet paper towel.</li>
</ol>
3. Preparing the MRSA for Infection (on the Day of Infection)
<ol>
<li>Dilute the overnight bacterial culture at 1:500 to 1:1000 with 10 mL of pre-warmed THB, in a 50 mL screw-capped tube.</li>
<li>Incubate at 37&deg;C for approximately 2.5 hours with shaking at 220 rpm, until A540 reaches 2.5.</li>
<li>Collect MRSA by centrifugation at 3,225 x g for 10 min at 4&deg;C.</li>
<li>Discard the supernatant.</li>
<li>Resuspend the bacterial pellet in 10 mL Dulbecco's phosphate buffered saline (DPBS).</li>
<li>Repeat steps 3 and 4.</li>
<li>Resuspend the bacterial pellet in DPBS at a desired concentration.</li>
<li>Serially dilute the bacterial suspension from 101 to 108.</li>
<li>Plate the diluted bacterial suspension onto blood agar plates.</li>
<li>Incubate the plates at 37&deg;C overnight.</li>
<li>Observe and record the hemolytic phenotype of the inocula.</li>
<li>Count the Colony Forming Units (CFU) number on the plate.</li>
<li>Calculate the inocula based on the CFU number on the plate.</li>
</ol>
4. Subcutaneous Infection of MRSA (on the Day of Infection and 3 Days Post-infection)
<ol>
<li>Inject subcutaneously 100 &mu;L bacterial suspension in the shaved area.</li>
<li>Observe the animals for 3 to 5 hours after injection to make sure the mice are alive.</li>
<li>Observe the lesion on the back of the animals daily and record the lesion area daily when it is needed. Lesion observation should include recording of lesion size and morphology. Both skin and muscle lesions are quantitated by multiplying the length and width of the lesion. Irregularly-shaped lesions need to be broken down into smaller symmetrical pieces, and each piece measured by the same method. Lesion measurements may also use a computer-assisted histomorphometric assessment program (ImageJ; open-source available from the NIH at <a href="http://rsb.info.nih.gov/ij">http://rsb.info.nih.gov/ij/</a>) 2.</li>
<li>Sacrifice the animals on day 3 post-infection by inhalation of isoflurane followed by cervical dislocation.</li>
<li>Observe and record the lesion on the skin.</li>
<li>Nick the skin with a pair of sterile scissors.</li>
<li>Peel the skin off carefully and observe and record the lesion on the muscle.</li>
<li>Excise the lesion and approximately 2 - 5 mm of the surrounding area.</li>
<li>Collect spleen and kidneys.</li>
<li>Homogenize the tissues using a tissue homogenizer or by repeated application of a plunger from a 1 mL syringe to a microfuge tube containing the tissue and 100 &mu;L of DPBS.</li>
<li>Add 900 &mu;L of DPBS to each tube.</li>
<li>Vortex the samples for 5 min.</li>
<li>Serially dilute the suspension with DPBS 101 to 106.</li>
<li>Plate the diluted suspensions on THA plates.</li>
</ol>
5. Representative Results:
<ol>
<li>Immediately after each subcutaneous injection, a bleb will be observed on the skin surface when infection is done correctly (Figure 1A). If no bleb is observed on the skin surface, the injection may be too deep, and this may affect the outcome of the infection (lesion size, CFU).</li>
<li>The bacterial suspension needs to be serially diluted and the CFU need to be examined on blood agar plates for each experiment. This step will yield important information: 1) whether the inocula have homogeneous phenotype; 2) the exact viable bacterial count for the infection.</li>
<li>The lesions and bacterial survival may be assessed at various time points post-infection. Here, we examined the infection on day 3 post-infection. The lesion sizes are analyzed on the skin surface (Figure 1B: 1x 109; Figure 1D: 1 x 107 CFU) and on the muscle surface (Figure 1C: 1x 109; Figure 1E: 1 x 107 CFU). The lesion area equals length (mm) x width (mm) may be measured for assessing the tissue damage (Figs. 2 A and B). This result may help determine the extent of tissue damage caused by a given virulence factor. Additionally, the lesions are excised and homogenized in DPBS, and plated to quantitate the CFU number (Figure 2C), which indicates the viability of the bacteria at the infection site.</li>
</ol>
<img src="/files/ftp_upload/2528/2528fig1.jpg" alt="Figure 1" /> 
Figure 1. The skin and muscle lesions. CD1 mice were inoculated subcutaneous on one flank with MRSA (LAC). Pictures were taken at time 0 and day 3 post-infection. (A) Time 0 post-infection (p.i.), (B)-(G) Day 3 p.i.; B, D. and F: skin lesions; C, E, and G: muscle lesions; B and C: 1x 109 CFU infected; D and E: 1x 107 CFU infected; F and G: mock.
<img src="/files/ftp_upload/2528/2528fig2.jpg" alt="Figure 2" /> 
Figure 2. Skin lesion size and viable bacteria count at the infection site on day 3 post-infection. Skin and muscle lesions on MRSA (LAC) infected CD1 mice. (A) Skin lesion size. (B) Muscle lesion size. (C) Total tissue CFU. H: 1 x 109 CFU inocula; L: 1 x 107 CFU inocula. *: p &lt; 0.05, Mann-Whitney test.

<ol>
	<li>Ahn, J. Y., Song, J. Y., Yun, Y. S., Jeong, G., Choi, I. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protection+of+Staphylococcus+aureus-infected+septic+mice+by+suppression+of+early+acute+inflammation+and+enhanced+antimicrobial+activity+by+ginsan.">Protection of Staphylococcus aureus-infected septic mice by suppression of early acute inflammation and enhanced antimicrobial activity by ginsan.</a> FEMS Immunol Med Microbiol. 46, 187-197 (2006).</li><li>Girish, V., Vijayalakshmi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Affordable+image+analysis+using+NIH+Image/ImageJ.">Affordable image analysis using NIH Image/ImageJ.</a> Indian J Cancer. 41, 47-47 (2004).</li><li>Hahn, B. L., Onunkwo, C. C., Watts, C. J., Sohnle, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systemic+dissemination+and+cutaneous+damage+in+a+mouse+model+of+staphylococcal+skin+infections.">Systemic dissemination and cutaneous damage in a mouse model of staphylococcal skin infections.</a> Microb Pathog. 47, 16-23 (2009).</li><li>Hruz, P., Zinkernagel, A. S., Jenikova, G., Botwin, G. J., Hugot, J. P., Karin, M., Nizet, V., Eckmann, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NOD2+contributes+to+cutaneous+defense+against+Staphylococcus+aureus+through+alpha-toxin-dependent+innate+immune+activation.">NOD2 contributes to cutaneous defense against Staphylococcus aureus through alpha-toxin-dependent innate immune activation.</a> Proc Natl Acad Sci U S A. 106, 12873-12878 (2009).</li><li>Ji, Y., Zhang, B., Van, S. F., Horn, P. W. a. r. r. e. n., Woodnutt, G., Burnham, M. K., Rosenberg, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+critical+staphylococcal+genes+using+conditional+phenotypes+generated+by+antisense+RNA.">Identification of critical staphylococcal genes using conditional phenotypes generated by antisense RNA.</a> Science. 293, 2266-2269 (2001).</li><li>Somerville, G. A., Beres, S. B., Fitzgerald, J. R., DeLeo, F. R., Cole, R. L., Hoff, J. S., Musser, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+serial+passage+of+Staphylococcus+aureus:+changes+in+physiology,+virulence+factor+production,+and+agr+nucleotide+sequence.">In vitro serial passage of Staphylococcus aureus: changes in physiology, virulence factor production, and agr nucleotide sequence.</a> J Bacteriol. 184, 1430-1437 (2002).</li><li>Tseng, C. W., Kyme, P., Low, J., Rocha, M. A., Alsabeh, R., Miller, L. G., Otto, M., Arditi, M., Diep, B. A., Nizet, V., Doherty, T. M., Beenhouwer, D. O., Liu, G. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Staphylococcus+aureus+Panton-Valentine+leukocidin+contributes+to+inflammation+and+muscle+tissue+injury.">Staphylococcus aureus Panton-Valentine leukocidin contributes to inflammation and muscle tissue injury.</a> PLoS One. 4, e6387-e6387 (2009).</li><li>von Kockritz-Blickwede, M., Rohde, M., Oehmcke, S., Miller, L. S., Cheung, A. L., Herwald, H., Foster, S., 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=Immunological+mechanisms+underlying+the+genetic+predisposition+to+severe+Staphylococcus+aureus+infection+in+the+mouse+model.">Immunological mechanisms underlying the genetic predisposition to severe Staphylococcus aureus infection in the mouse model.</a> Am J Pathol. 173, 1657-1668 (2008).</li></ol>

No conflicts of interest declared.

<ol>
<li>The murine skin and soft tissue infection model is a powerful tool for in vivo virulence assessment of a pathogen. The pathogenicity of S. aureus in skin and soft tissue infection may vary depending on a number of parameters. These include inoculum size, bacterial growth phase, depth of inoculation, age of mice, and the mouse genetic background 7, 8. When examining the virulence function using this model, it is critical to control for these parameters to ensure that results will be consistent. We have ...

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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>THB</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>95025-314</td>
<td>&nbsp;</td>
<tr>
<td>DPBS</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>21-031-CV</td>
<td>&nbsp;</td>
<tr>
<td>1 ml syringe</td>
<td>&nbsp;</td>
<td>BD</td>
<td>309602</td>
<td>&nbsp;</td>
<tr>
<td>27G1/2 needle</td>
<td>&nbsp;</td>
<td>BD</td>
<td>305109</td>
<td>&nbsp;</td>
<tr>
<td>Sheep Blood Agar (TSA)</td>
<td>&nbsp;</td>
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<td>90004-328</td>
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subcutaneous infection of methicillin resistant staphylococcus aureus (mrsa)

MRSA is a worldwide threat to public health, and MRSA skin and soft-tissue infections now account for more than half of all soft-tissue infections in the United States. Among soft-tissue infections, myositis, pyomyositis, and necrotizing fasciitis have been increasingly reported in association with MRSA arising from the community. To understand the interplay between MRSA and host immunity leading to more severe infection, the availability of animal models is critical, permitting the study of host and bacterial factors. Several infection models have been introduced to assess the pathogenesis of S. aureus during superficial skin infection. Here, we describe a subcutaneous infection model that examines the skin, subcutaneous, and muscle pathologies.

Watch this Scientific Journal Video about Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA at JoVE.com

Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA

Murine skin and soft tissue infection model is utilized for assessing the virulence function of methicillin resistant Staphylococcus aureus (MRSA) and the host immunological responses. Here, we presented a subcutaneous infection model for skin and soft tissue infection.

Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)

MRSA is a worldwide threat to public health, and MRSA skin and soft-tissue infections now account for more than half of all soft-tissue infections in the ...

subcutaneous-infection-methicillin-resistant-staphylococcus-aureus

Research

JoVE Journal

Immunology and Infection

22.9K 조회수.  Cedars-Sinai Medical Center. Murine 피부와 부드러운 조직 감염 모델은 methicillin 내성 포도상 구균 (MRSA) 및 호스트 면역 응답의 독성 기능을 평가하기위한 활용합니다. 여기, 우리는 피부와 부드러운 조직 감염 피하 감염 모델을 소개하고 있습니다.

비디오: Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA

The Use of Drip Flow and Rotating Disk Reactors for Staphylococcus aureus Biofilm Analysis

Most microbes in nature are thought to exist as surface-associated communities in biofilms.1 Bacterial biofilms are encased within a matrix and attached to a surface.2 Biofilm formation and development are commonly studied in the laboratory using batch systems such as microtiter plates or flow systems, such as flow-cells. These methodologies are useful for screening mutant and chemical libraries (microtiter plates)3 or growing biofilms for visualization (flow cells)4. Here we present detailed protocols for growing Staphylococcus aureus in two additional types of flow system biofilms: the drip flow biofilm reactor and the rotating disk biofilm reactor.
Drip flow biofilm reactors are designed for the study of biofilms grown under low shear conditions.5 The drip flow reactor consists of four parallel test channels, each capable of holding one standard glass microscope slide sized coupon, or a length of catheter or stint. The drip flow reactor is ideal for microsensor monitoring, general biofilm studies, biofilm cryosectioning samples, high biomass production, medical material evaluations, and indwelling medical device testing.6,7,8,9
The rotating disk reactor consists of a teflon disk containing recesses for removable coupons.10 The removable coupons can by made from any machinable material. The bottom of the rotating disk contains a bar magnet to allow disk rotation to create liquid surface shear across surface-flush coupons. The entire disk containing 18 coupons is placed in a 1000 mL glass side-arm reactor vessel. A liquid growth media is circulated through the vessel while the disk is rotated by a magnetic stirrer. The coupons are removed from the reactor vessel and then scraped to collect the biofilm sample for further study or microscopy imaging. Rotating disc reactors are designed for laboratory evaluations of biocide efficacy, biofilm removal, and performance of anti-fouling materials.9,11,12,13

The Use of Drip Flow and Rotating Disk Reactors for Staphylococcus aureus Biofilm Analysis

Protocols for utilizing open system flow biofilms with drip flow reactors and rotating disk reactors are presented in detail.

Most microbes in nature are thought to exist as surface-associated communities in biofilms.1  Bacterial biofilms are encased within a matrix and attached ...

Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus (MRSA) in Rat

Endovascular infections, including endocarditis, are life-threatening infectious syndromes1-3. Staphylococcus aureus is the most common world-wide cause of such syndromes with unacceptably high morbidity and mortality even with appropriate antimicrobial agent treatments4-6. The increase in infections due to methicillin-resistant S. aureus (MRSA), the high rates of vancomycin clinical treatment failures and growing problems of linezolid and daptomycin resistance have all further complicated the management of patients with such infections, and led to high healthcare costs7, 8. In addition, it should be emphasized that most recent studies with antibiotic treatment outcomes have been based in clinical settings, and thus might well be influenced by host factors varying from patient-to-patient. Therefore, a relevant animal model of endovascular infection in which host factors are similar from animal-to-animal is more crucial to investigate microbial pathogenesis, as well as the efficacy of novel antimicrobial agents. Endocarditis in rat is a well-established experimental animal model that closely approximates human native valve endocarditis. This model has been used to examine the role of particular staphylococcal virulence factors and the efficacy of antibiotic treatment regimens for staphylococcal endocarditis. In this report, we describe the experimental endocarditis model due to MRSA that could be used to investigate bacterial pathogenesis and response to antibiotic treatment.

Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus MRSA in Rat

Experimental rat endocarditis model due to methicillin-resistant S. aureus.

Endovascular infections, including endocarditis, are life-threatening infectious syndromes1-3. Staphylococcus aureus is the most common world-wide cause ...

Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source

S. aureus is a pathogenic bacterium that requires iron to carry out vital metabolic functions and cause disease. The most abundant reservoir of iron inside the human host is heme, which is the cofactor of hemoglobin. To acquire iron from hemoglobin, S. aureus utilizes an elaborate system known as the iron-regulated surface determinant (Isd) system1. Components of the Isd system first bind host hemoglobin, then extract and import heme, and finally liberate iron from heme in the bacterial cytoplasm2,3. This pathway has been dissected through numerous in vitro studies4-9. Further, the contribution of the Isd system to infection has been repeatedly demonstrated in mouse models8,10-14. Establishing the contribution of the Isd system to hemoglobin-derived iron acquisition and growth has proven to be more challenging. Growth assays using hemoglobin as a sole iron source are complicated by the instability of commercially available hemoglobin, contaminating free iron in the growth medium, and toxicity associated with iron chelators. Here we present a method that overcomes these limitations. High quality hemoglobin is prepared from fresh blood and is stored in liquid nitrogen. Purified hemoglobin is supplemented into iron-deplete medium mimicking the iron-poor environment encountered by pathogens inside the vertebrate host. By starving S. aureus of free iron and supplementing with a minimally manipulated form of hemoglobin we induce growth in a manner that is entirely dependent on the ability to bind hemoglobin, extract heme, pass heme through the bacterial cell envelope and degrade heme in the cytoplasm. This assay will be useful for researchers seeking to elucidate the mechanisms of hemoglobin-/heme-derived iron acquisition in S. aureus and possibly other bacterial pathogens.

Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source

Here we describe a growth assay for Staphylococcus aureus using hemoglobin as the sole source of available nutrient iron. This assay establishes the role of bacterial factors involved in hemoglobin-derived iron acquisition.

S. aureus is a pathogenic bacterium that requires iron to  carry out vital metabolic functions and cause disease. The most abundant  reservoir of iron ...

Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus

Staphylococcal Cassette Chromosome mec (SCCmec) typing is a very important molecular tool for understanding the epidemiology and clonal strain relatedness of methicillin-resistant Staphylococcus aureus (MRSA), particularly with the emerging outbreaks of community-associated MRSA (CA-MRSA) occurring on a worldwide basis. Traditional PCR typing schemes classify SCCmec by targeting and identifying the individual mec and ccr gene complex types, but require the use of many primer sets and multiple individual PCR experiments. We designed and published a simple multiplex PCR assay for quick-screening of major SCCmec types and subtypes I to V, and later updated it as new sequence information became available. This simple assay targets individual SCCmec types in a single reaction, is easy to interpret and has been extensively used worldwide. However, due to the sophisticated nature of the assay and the large number of primers present in the reaction, there is the potential for difficulties while adapting this assay to individual laboratories. To facilitate the process of establishing a MRSA SCCmec assay, here we demonstrate how to set up our multiplex PCR assay, and discuss some of the vital steps and procedural nuances that make it successful.

Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus

We demonstrate a simple multiplex PCR assay for quick-screening and typing of Staphylococcal Cassette Chromosome mec (SCCmec) types I-V for methicillin-resistant Staphylococcus aureus, and provide some of the vital steps and procedural nuances that make it successful for adapting this assay to individual laboratories.

Staphylococcal Cassette Chromosome mec (SCCmec) typing  is a very important molecular tool for understanding the epidemiology and  clonal strain ...

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy

We present methods to study the effect of phenol soluble modulins (PSMs) and other toxins produced and secreted by Staphylococcus aureus on neutrophils. To study the effects of the PSMs on neutrophils we isolate fresh neutrophils using density gradient centrifugation. These neutrophils are loaded with a dye that fluoresces upon calcium mobilization. The activation of neutrophils by PSMs initiates a rapid and transient increase in the free intracellular calcium concentration. In a flow cytometry experiment this rapid mobilization can be measured by monitoring the fluorescence of a pre-loaded dye that reacts to the increased concentration of free Ca2+. Using this method we can determine the PSM concentration necessary to activate the neutrophil, and measure the effects of specific and general inhibitors of the neutrophil activation.	
	To investigate the expression of the PSMs in the intracellular space, we have constructed reporter fusions of the promoter of the PSM&alpha; operon to GFP. When these reporter strains of S. aureus are phagocytosed by neutrophils, the induction of expression can be observed using fluorescence microscopy.

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy

We present methods to study the effect of PSMs and other toxins secreted by Staphylococcus aureus on neutrophils using flow cytometry and fluorescence microscopy.

We present methods to study the effect of phenol soluble modulins (PSMs)  and other toxins produced and secreted by Staphylococcus  aureus on neutrophils. ...

Demonstrating a Multi-drug Resistant Mycobacterium tuberculosis Amplification Microarray

Simplifying microarray workflow is a necessary first step for creating MDR-TB microarray-based diagnostics that can be routinely used in lower-resource environments. An amplification microarray combines asymmetric PCR amplification, target size selection, target labeling, and microarray hybridization within a single solution and into a single microfluidic chamber. A batch processing method is demonstrated with a 9-plex asymmetric master mix and low-density gel element microarray for genotyping multi-drug resistant Mycobacterium tuberculosis (MDR-TB). The protocol described here can be completed in 6 hr and provide correct genotyping with at least 1,000 cell equivalents of genomic DNA. Incorporating on-chip wash steps is feasible, which will result in an entirely closed amplicon method and system. The extent of multiplexing with an amplification microarray is ultimately constrained by the number of primer pairs that can be combined into a single master mix and still achieve desired sensitivity and specificity performance metrics, rather than the number of probes that are immobilized on the array. Likewise, the total analysis time can be shortened or lengthened depending on the specific intended use, research question, and desired limits of detection. Nevertheless, the general approach significantly streamlines microarray workflow for the end user by reducing the number of manually intensive and time-consuming processing steps, and provides a simplified biochemical and microfluidic path for translating microarray-based diagnostics into routine clinical practice.

Demonstrating a Multi-drug Resistant Mycobacterium tuberculosis Amplification Microarray

An amplification microarray combines asymmetric PCR amplification and microarray hybridization into a single chamber, which significantly streamlines microarray workflow for the end user. Simplifying microarray workflow is a necessary first step for creating microarray-based diagnostics that can be routinely used in lower-resource environments.

Simplifying microarray workflow is a necessary first step for creating MDR-TB microarray-based diagnostics that can be routinely used in lower-resource ...

Targeting Biofilm Associated Staphylococcus aureus Using Resazurin Based Drug-susceptibility Assay

Most pathogenic bacteria are able to form biofilms during infection, but due to the difficulty of manipulating and assessing biofilms, the vast majority of laboratory work is conducted with planktonic cells. Here, we describe a peg plate biofilm assay as performed with Staphylococcus aureus. Bacterial biofilms are grown on pegs attached to a 96-well microtiter plate lid, washed through gentle submersion in buffer, and placed in a drug challenge plate. After subsequent incubation they are again washed and moved to a final recovery plate, in which the fluorescent dye resazurin serves as a viability indicator. This assay offers greatly increased ease-of-use, reliability, and reproducibility, as well as a wealth of data when conducted as a kinetic read. Moreover, this assay can be adapted to a medium-throughput drug screening approach by which an endpoint fluorescent readout is taken instead, offering a path for drug discovery efforts.

Targeting Biofilm Associated Staphylococcus aureus Using Resazurin Based Drug-susceptibility Assay

Most bacterial infections produce a biofilm. By virtue of their environment, biofilm associated bacteria are often phenotypically drug resistant. Novel antibacterial molecules that kill bacteria in biofilms are thus a high priority. We establish an assay to quickly screen for antimicrobial compounds that are effective at eradicating biofilms.

Most pathogenic bacteria are able to form biofilms during infection, but due to the difficulty of manipulating and assessing biofilms, the vast majority ...

Protective Efficacy and Pulmonary Immune Response Following Subcutaneous and Intranasal BCG Administration in Mice

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data have encouraged pulmonary tuberculosis vaccines as a promising strategy to prevent pulmonary disease, which is responsible for transmission. In this work, we describe the methodology used to demonstrate in the mouse model the benefits of intranasal BCG vaccination when compared to subcutaneous. Our data revealed greater protective efficacy following intranasal BCG administration. In addition, our results indicate that pulmonary vaccination triggers a higher immune response in lungs, including Th1 and Th17 responses, as well as an increase of immunoglobulin A (IgA) concentration in respiratory airways. Our data show correlation between protective efficacy and the presence of IL17-producing cells in lungs post-Mycobacterium tuberculosis challenge, suggesting a role for this cytokine in the protective response conferred by pulmonary vaccination. Finally, we detail the global workflow we have developed to study respiratory vaccination in the mouse model, which could be extrapolated to other tuberculosis vaccines, apart from BCG, targeting the mucosal response or other pulmonary routes of administration such as the intratracheal or aerosol.

We herein detail the methodology followed to compare protective efficacy and lung immune response induced by intranasal and subcutaneous immunization with BCG in mouse model. Our results show the benefits of pulmonary vaccination and suggest a role for IL17-mediated response in vaccine-induced protection.

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data ...

Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR (RS-PCR)

The ribosomal spacer PCR (RS-PCR) is a highly resolving and robust genotyping method for S. aureus that allows a high throughput at moderate costs and is, therefore, suitable to be used for routine purposes. For best resolution, data evaluation and data management, a miniaturized electrophoresis system is required. Together with such an electrophoresis system and the in-house developed software (freely available here) assignment of the pattern of bands to a genotype is standardized and straight forward. DNA extraction is simple (boiling prep), setting-up of the reactions is easy and they can be run on any standard PCR machine. PCR cycling is common except prolonged ramping and elongation times. Compared to spa typing and Multi Locus Sequence Typing (MLST), RS-PCR does not require DNA sequencing what simplifies the analysis considerably and allows a high throughput. Furthermore, the resolution for bovine strains of S. aureus is at least as good as spa typing and better than MLST or pulsed-field gel electrophoresis (PFGE). The RS-PCR data base includes presently a total of 141 genotypes and variants. The method is highly associated with the virulence gene pattern, contagiosity and pathogenicity of S. aureus strains involved in bovine mastitis. S. aureus genotype B (GTB) is contagious and causes herds problems causing large costs in the Switzerland and other European countries. All the other genotypes observed in Switzerland infect individual cows and quarters. Genotyping by RS-PCR allows the reliable prediction of the epidemiological and the pathogenic potential of S. aureus involved in bovine intramammary infection (IMI), two key factors for clinical veterinary medicine. Because of these beneficial properties together with moderate costs and a high sample throughput the goal of this publication is to give a detailed, step-by-step protocol for easily establishing and running RS-PCR for genotyping S. aureus in other laboratories.

Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR

Here, ribosomal spacer PCR (RS-PCR) is used together with a miniaturized electrophoresis system as a fast and high resolution method for genotyping S. aureus at moderate costs allowing a high throughput.

The ribosomal spacer PCR (RS-PCR) is a highly resolving and robust genotyping method for S. aureus that allows a high throughput at moderate costs and is, ...

Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus

One important feature of the major opportunistic human pathogen Staphylococcus aureus is its extraordinary ability to rapidly acquire resistance to antibiotics. Genomic studies reveal that S. aureus carries many virulence and resistance genes located in mobile genetic elements, suggesting that horizontal gene transfer (HGT) plays a critical role in S. aureus evolution. However, a full and detailed description of the methodology used to study HGT in S. aureus is still lacking, especially regarding natural transformation, which has been recently reported in this bacterium. This work describes three protocols that are useful for the in vitro investigation of HGT in S. aureus: conjugation, phage transduction, and natural transformation. To this aim, the cfr gene (chloramphenicol/florfenicol resistance), which confers the Phenicols, Lincosamides, Oxazolidinones, Pleuromutilins, and Streptogramin A (PhLOPSA)-resistance phenotype, was used. Understanding the mechanisms through which S. aureus transfers genetic materials to other strains is essential to comprehending the rapid acquisition of resistance and helps to clarify the modes of dissemination reported in surveillance programs or to further predict the spreading mode in the future.

Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus

We describe here three different protocols for the in vitro investigation of conjugation, transduction, and natural transformation in Staphylococcus aureus.

One important feature of the major opportunistic human pathogen Staphylococcus aureus is its extraordinary ability to rapidly acquire resistance to ...