This work has been supported by Elizabeth E. Kennedy Research Award.

1，准备生产菌株的<ol><li>连胜肺炎球菌菌株对细菌生产的5％羊血的胰蛋白酶大豆琼脂从-80°C冰箱个股板块进行测试。 注：该菌株的抑制作用被测试的初期生长，使用血板大大增加了实验的可重复性。此外，其他能产生细菌素的非肺炎球菌菌株可使用虽然生长条件可能需要修改为特定的有机体。我们已经用缓症链球菌和乳酸乳球菌中的覆盖试验成功。 </li><li>在37℃下孵育平板过夜（O / N），用5％的CO 2。 </li><li>该生产菌株的培养后，吹打过氧化氢酶的3000至4000台准备胰酶大豆琼脂（TSA）平板上有25ml的TSA板，并使用无菌玻璃珠流传过氧化氢酶的解决方案。让板干燥下约10分钟生物安全柜。 </li><li>收集细菌的数量明显到一个枪头。刺枪头到TSA的干板。 注：不止一个的生产菌株可捅成一个单一的TSA板。它使得得到的光晕不重叠是很重要的，以空间出来的刺伤。 <ol><li>如果可能的话，包括已知的细菌素生产的，作为阳性对照，并在覆盖作为阴性对照使用的菌株。 注：阳性和阴性对照是此前已公布，并根据要求提供10。 </li></ol></li><li>孵育TSA板包含多个刺，在37℃，5％CO 2中6小时。 </li></ol>叠加应变2制作甘油股票<ol><li>备之前，覆盖测定当天甘油原液（培养物中加入甘油后生长至中期指数期，然后保存于-80℃）。接种肺炎球菌的海峡殖民地5-10AIN为敏感或信息素的分泌托德休伊特中有0.5％的酵母提取物（THY）进行测试。 注：BLPC诱导记者，施工已如前所述2株可根据要求提供。 </li><li>孵育5-10殖民地玻璃管用5毫升THY与盖紧盖子在37℃水浴中，不晃动。 </li><li>孵育培养物在37℃，直到它们达到的OD 0.3 620〜0.5。 注意：这将需要大约4-5小时，具体取决于所使用的菌株。 <ol><li>轻轻翻转试管前测量外径几次。 </li></ol></li><li>如果实验不能在同一天进行，或者在将来的应变会被多次使用，使甘油原液和恢复试验在稍后的日期。甘油股，加甘油文化的20％的最终浓度。分装到培养的1.5 ml离心管中，并储存在-80℃。注：样品可为stored几个月在-80℃。如果不是在甘油的股票，直接利用样本进行叠加分析。 </li></ol> 3，叠加分析<ol><li>之前叠加应用，混合叠加组成部分。在15 mL锥形管，加入5 ml祢，过氧化氢酶3,000-4,000 U和200微升这是不是长大的那一天，或者是在室温下解冻文化的甘油覆盖应变肉汤培养物。如果使用报告菌株，添加50μl的第X-gal的（40毫克/毫升），以覆盖混合物。用一个锥形管，每盘。 </li><li>在室温下平衡，然后加入熔融的TSA的覆盖混合物。 </li><li>从孵化器刺伤应变删除TSA板。熔化的固体TSA微波炉，并保持在55℃水浴中待用。加入熔融TSA 3毫升与1.5％琼脂冷却至55℃以叠加混合​​物。 <ol><li>立即移液之前，请准备叠加混合，混合物会开始凝固很快。注：如果叠加电镀开始之前固化，其结果将是无法解释的。 </li></ol></li><li>移液器向上和向下几次了500毫升吸管小心不要引入气泡到混合物混合叠加混合物。慢慢的吸液管直接覆盖混合到捅TSA板。保持在台式数分钟使琼脂变硬的板。 <ol><li>不要旋转盘来分发叠加混合，这将拉动从被刺的文化发展到覆盖。 </li></ol></li><li>小心地TSA板覆盖到含有5％的CO 2 O 2 / N（约16-18小时）37℃培养箱中培养。 </li><li>过夜生长后观察平板上。该板块应该会出现在覆盖株生长不透明的，除非发生抑制或信息素信号的地方的地方。这些将分别出现在左右应变刺伤清除或蓝色区域。 注：虽然测量电的蓝色或结算的直径对此语句可以用于定量评估来确定，在直径不同也可取决于细菌的被刺到板的量。覆盖法是一种定性分析，任何定量评估应谨慎解释。任何可见的结算相比于阴性对照被视为活性。 </li></ol>

<ol>
	<li>Dawid, S., Roche, A. M., Weiser, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+blp+bacteriocins+of+Streptococcus+pneumoniae+mediate+intraspecies+competition+both+in+vitro+and+in+vivo.">The blp bacteriocins of Streptococcus pneumoniae mediate intraspecies competition both in vitro and in vivo.</a> Infect Immun. 75 (1), 443-451 (2007).</li><li>Sawa, 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=Isolation+and+characterization+of+enterocin+W,+a+novel+two-peptide+lantibiotic+produced+by+Enterococcus+faecalis+NKR-4-1.">Isolation and characterization of enterocin W, a novel two-peptide lantibiotic produced by Enterococcus faecalis NKR-4-1.</a> Appl Environ Microbiol. 78 (3), 900-903 (2012).</li><li>Kochan, T. J., Dawid, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+HtrA+protease+of+Streptococcus+pneumoniae+controls+density-dependent+stimulation+of+the+bacteriocin+blp+locus+via+disruption+of+pheromone+secretion.">The HtrA protease of Streptococcus pneumoniae controls density-dependent stimulation of the bacteriocin blp locus via disruption of pheromone secretion.</a> J Bacteriol. 195 (7), 1561-1572 (2013).</li><li>Lux, T., Nuhn, M., Hakenbeck, R., Reichmann, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diversity+of+bacteriocins+and+activity+spectrum+in+Streptococcus+pneumoniae.">Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae.</a> J Bacteriol. 189 (21), 7741-7751 (2007).</li><li>Reichmann, P., Hakenbeck, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allelic+variation+in+a+peptide-inducible+two-component+system+of+Streptococcus+pneumoniae.">Allelic variation in a peptide-inducible two-component system of Streptococcus pneumoniae.</a> FEMS Microbiol Lett. 190 (2), 231-236 (2000).</li><li>Saizieu, 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=Microarray-based+identification+of+a+novel+Streptococcus+pneumoniae+regulon+controlled+by+an+autoinduced+peptide.">Microarray-based identification of a novel Streptococcus pneumoniae regulon controlled by an autoinduced peptide.</a> J Bacteriol. 182 (17), 4696-4703 (2000).</li><li>Barbour, A., Philip, K., Muniandy, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+production,+purification,+characterization+and+mechanism+of+action+of+salivaricin+9+lantibiotic+produced+by+Streptococcus+salivarius+NU10.">Enhanced production, purification, characterization and mechanism of action of salivaricin 9 lantibiotic produced by Streptococcus salivarius NU10.</a> PLoS One. 8 (10), 77751 (2013).</li><li>Wladyka, 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=Isolation,+biochemical+characterization,+and+cloning+of+a+bacteriocin+from+the+poultry-associated+Staphylococcus+aureus+strain+CH-91.">Isolation, biochemical characterization, and cloning of a bacteriocin from the poultry-associated Staphylococcus aureus strain CH-91.</a> Appl Microbiol Biotechnol. 97 (16), 7229-7239 (2013).</li><li>Shea, E. F., 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=Bactofencin+a,+a+new+type+of+cationic+bacteriocin+with+unusual+immunity.">Bactofencin a, a new type of cationic bacteriocin with unusual immunity.</a> 4 (6), 00498-00413 (2013).</li><li>Son, M. 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=Conserved+mutations+in+the+pneumococcal+bacteriocin+transporter+gene,+blpA,+result+in+a+complex+population+consisting+of+producers+and+cheaters.">Conserved mutations in the pneumococcal bacteriocin transporter gene, blpA, result in a complex population consisting of producers and cheaters.</a> MBio. 2 (5), (2011).</li><li>Kochan, T. J., Dawid, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+HtrA+protease+of+Streptococcus+pneumoniae+controls+density-dependent+stimulation+of+the+bacteriocin+blp+locus+via+disruption+of+pheromone+secretion.">The HtrA protease of Streptococcus pneumoniae controls density-dependent stimulation of the bacteriocin blp locus via disruption of pheromone secretion.</a> J Bacteriol. 195, 1561-1572 (2013).</li><li>Widdick, D. 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The authors have nothing to disclose.

这个覆盖测定法是一种快速的方式来确定用于细菌素生产活动的范围，并表明肺炎球菌菌株之间可能出现的竞争性相互作用。覆盖测定法可适于用于筛选多株为细菌素生产上的单个板。我们已通过使用一个48针复制器从一个半到96孔板的接种SBA板成功筛选大应变的集合与该测定。隔夜培养后，成长正在使用的复制和穿孔板与复制的引脚的琼脂表面转移到TSA的板块。 被调节在像?...

肺炎链球菌 ，鼻咽部的多种微生物社会的共同殖民者，能够通过生产细菌产生抗菌肽（细菌素）与其他肺炎球菌和密切相关的物种竞争。每一个完全测序肺炎球菌菌株检测到包含最新版本的B acteriocin- 升 IKE p eptide轨迹，BLP的。细菌素生产由肺炎球菌已被证明是既在体外的结果，并在体内竞争1-4重要。竞争的动力学是由沿与同源免疫蛋白多样的细菌素的表达响应于一个特定的肽信息素的影响。感应的BLP轨迹是由一个群体感应系统，其中的肽信息素，BLPC，结合到传感器激酶，BlpH控制，并开始导致信号级联转录BLP轨迹5,6。有BLPC四个等位基因变异，每绑定到其同源BlpH 6。对于细胞生存其自身细菌素的影响，其编码同源免疫蛋白的基因被转录于同一操纵子作为各细菌的基因。如果竞争者应变是不能够上调BLP轨迹响应于外源信息素，或如菌株缺少所需的保护的特定免疫基因发生杀伤。该转运体复合物，BlpAB是所必需的肽信息素的分泌，加工和细菌的肽2,4。最近，它已被证明，肺炎球菌菌株的显著一部分是“骗子”，这意味着他们在blpA基因，使它们无法分泌信息素和细菌素1,2保守突变。这些菌株能够外感BLPC 2所分泌的嘶鸣回应无聊株允许生产的免疫蛋白。 虽然细菌素，从上清液粗制剂可以从生产者菌株用生化方法步骤，以达到纯度来制备，这种方法是不实用的筛选分离的大的集合，如果细菌素的表达水平是低的肉汤生长培养2,7- 9。覆盖测定法作为一种快速的方法来调查可能存在的在体外的菌株之间的竞争动态。要做到这一点，肺炎球菌菌株是预先接种到琼脂平板，让它生长，以达到局部细菌浓度足以诱导BLP轨迹。第二应变，然后接种到熔融的软琼脂溶液中，然后施加在预接种菌株来测试灵敏度。以评估为BLP轨迹（独立抑制活性）的活性，菌株可与一系列日来覆盖稀土前面所述BLPC记者株。这些菌株被构造成包含三个不同blpH等位基因是由肺炎链球菌分泌的三种最常见的BLPC信息素响应之一。记者菌株具有一个集成的lacZ基因，该基因是一个BlpH依赖的启动子的控制下，并携带的缺失在BLPC基因，防止自励10,11。

<table border="0" cellpadding="0" cellspacing="0" width="753">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Name of Material/ Equipment</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:351px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Trypticase Soy Agar with 5% Sheep Blood</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">B21261X&#160;</td>
			<td>For growth from freezer cultures</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Catalase</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">C100-500mg</td>
			<td>4,741 Units per plate</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Todd Hewitt Broth + Yeast Extract (THY)</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">DF0492-17-6&#160;</td>
			<td>30 g of THB, 5 g yeast extract, 1 L ddH20 autoclave</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Trypticase Soy Broth + Agar plates (TSA)</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">B11768&#160;</td>
			<td>30 g of TS, 15 g agar, 1 L ddH20 autoclave</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">5-Bromo-4-chloro-3-indolyl &#946;-D-galactopyranoside (X-gal)</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">B4252-50MG</td>
			<td>Dissolve in dimethylformamide</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Petri dishes</td>
			<td style="width:71px;">Fisher</td>
			<td>FB0875712</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Spectrophometer</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>Measures the OD620 of cultures</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">37 &#176;C water bath</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">37 &#176;C incubator with 5% CO2</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">15 ml conical tube</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

using the overlay assay to qualitatively measure bacterial production of and sensitivity to pneumococcal bacteriocins

Streptococcus pneumoniae colonizes the highly diverse polymicrobial community of the nasopharynx where it must compete with resident organisms. We have shown that bacterially produced antimicrobial peptides (bacteriocins) dictate the outcome of these competitive interactions. All fully-sequenced pneumococcal strains harbor a bacteriocin-like peptide (blp) locus. The blp locus encodes for a range of diverse bacteriocins and all of the highly conserved components needed for their regulation, processing, and secretion. The diversity of the bacteriocins found in the bacteriocin immunity region (BIR) of the locus is a major contributor of pneumococcal competition. Along with the bacteriocins, immunity genes are found in the BIR and are needed to protect the producer cell from the effects of its own bacteriocin. The overlay assay is a quick method for examining a large number of strains for competitive interactions mediated by bacteriocins. The overlay assay also allows for the characterization of bacteriocin-specific immunity, and detection of secreted quorum sensing peptides. The assay is performed by pre-inoculating an agar plate with a strain to be tested for bacteriocin production followed by application of a soft agar overlay containing a strain to be tested for bacteriocin sensitivity. A zone of clearance surrounding the stab indicates that the overlay strain is sensitive to the bacteriocins produced by the pre-inoculated strain. If no zone of clearance is observed, either the overlay strain is immune to the bacteriocins being produced or the pre-inoculated strain does not produce bacteriocins. To determine if the blp locus is functional in a given strain, the overlay assay can be adapted to evaluate for peptide pheromone secretion by the pre-inoculated strain. In this case, a series of four lacZ-reporter strains with different pheromone specificity are used in the overlay.

中有重叠测定两种可能的结果。它应当能够看到被刺菌株生长过夜孵育后。在图1A中，覆盖层的应变是敏感的正在生产的细菌素。间隙的区域可以显现周边刺伤应变。此外，被刺应变到覆盖混合物的旋涡是可能的，并且可以在图1A中可以看出。在图1B中，覆盖应变都难被分泌所指出的不存在包围短截卤代的细菌素。它也有可能是在被刺应变不分泌细菌素。对于?...

Watch this Scientific Journal Video about Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins at JoVE.com

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Competition in Streptococcus pneumoniae is mediated by bacteriocins, small antimicrobial peptides with inhibitory activity towards pneumococcus and other related species.&#160; Here we describe an optimized bacterial overlay assay that allows for the characterization of bacteriocin activity and inhibitory spectrum, bacteriocin-specific immunity, and detection of secreted quorum sensing peptides.

使用复分析定性测量细菌生产和敏感性，以肺炎球菌细菌素

Streptococcus pneumoniae colonizes the highly diverse polymicrobial community of the nasopharynx where it must compete with resident organisms.  We have ...

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Research

JoVE Journal

Immunology and Infection

13.4K 次观看.  University of Michigan. Competition in Streptococcus pneumoniae is mediated by bacteriocins, small antimicrobial peptides with inhibitory activity towards pneumococcus and other related species.  Here we describe an optimized bacterial overlay assay that allows for the characterization of bacteriocin activity and inhibitory spectrum, bacteriocin-specific immunity, and detection of secreted quorum sensing peptides. 

视频: Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Using Luciferase to Image Bacterial Infections in Mice

Imaging is a valuable technique that can be used to monitor biological processes. In particular, the presence of cancer cells, stem cells, specific immune cell types, viral pathogens, parasites and bacteria can be followed in real-time within living animals 1-2. Application of bioluminescence imaging to the study of pathogens has advantages as compared to conventional strategies for analysis of infections in animal models3-4. Infections can be visualized within individual animals over time, without requiring euthanasia to determine the location and quantity of the pathogen. Optical imaging allows comprehensive examination of all tissues and organs, rather than sampling of sites previously known to be infected. In addition, the accuracy of inoculation into specific tissues can be directly determined prior to carrying forward animals that were unsuccessfully inoculated throughout the entire experiment. Variability between animals can be controlled for, since imaging allows each animal to be followed individually. Imaging has the potential to greatly reduce animal numbers needed because of the ability to obtain data from numerous time points without having to sample tissues to determine pathogen load3-4.
This protocol describes methods to visualize infections in live animals using bioluminescence imaging for recombinant strains of bacteria expressing luciferase. The click beetle (CBRLuc) and firefly luciferases (FFluc) utilize luciferin as a substrate5-6. The light produced by both CBRluc and FFluc has a broad wavelength from 500 nm to 700 nm, making these luciferases excellent reporters for the optical imaging in living animal models7-9. This is primarily because wavelengths of light greater than 600 nm are required to avoid absorption by hemoglobin and, thus, travel through mammalian tissue efficiently. Luciferase is genetically introduced into the bacteria to produce light signal10. Mice are pulmonary inoculated with bioluminescent bacteria intratracheally to allow monitoring of infections in real time. After luciferin injection, images are acquired using the IVIS Imaging System. During imaging, mice are anesthetized with isoflurane using an XGI-8 Gas Anethesia System. Images can be analyzed to localize and quantify the signal source, which represents the bacterial infection site(s) and number, respectively. After imaging, CFU determination is carried out on homogenized tissue to confirm the presence of bacteria. Several doses of bacteria are used to correlate bacterial numbers with luminescence. Imaging can be applied to study of pathogenesis and evaluation of the efficacy of antibacterial compounds and vaccines.

Methods for bioluminescence imaging of bacterial infections in living animals are decribed. Pathogens are modified to express luciferase allowing optical whole body imaging of infections in live animals. Animal models can be infected with luciferase expressing pathogens and the resulting course of disease visualized in real-time by bioluminescence imaging.

用荧光素酶在小鼠细菌性感染的形象

Imaging is a valuable technique that can be used to monitor biological processes.  In particular, the presence of cancer cells, stem cells, specific ...

科研

免疫与感染

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb (BCG lux/M.Tb lux)

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal titers. Studies of serum bactericidal titers in response to childhood vaccines have enabled us to develop and validate cut-off levels for protective immune responses and such cut-offs are in routine use. No such assays have been taken forward into the routine assessment of vaccines that induce primarily cell-mediated immunity in the form of effector T cell responses, such as TB vaccines. In the animal model, the performance of a given vaccine candidate is routinely evaluated in standardized bactericidal assays, and all current novel TB-vaccine candidates have been subjected to this step in their evaluation prior to phase 1 human trials. The assessment of immunogenicity and therefore likelihood of protective efficacy of novel anti-TB vaccines should ideally undergo a similar step-wise evaluation in the human models now, including measurements in bactericidal assays.
Bactericidal assays in the context of tuberculosis vaccine research are already well established in the animal models, where they are applied to screen potentially promising vaccine candidates. Reduction of bacterial load in various organs functions as the main read-out of immunogenicity. However, no such assays have been incorporated into clinical trials for novel anti-TB vaccines to date.
Although there is still uncertainty about the exact mechanisms that lead to killing of mycobacteria inside human macrophages, the interaction of macrophages and T cells with mycobacteria is clearly required. The assay described in this paper represents a novel generation of bactericidal assays that enables studies of such key cellular components with all other cellular and humoral factors present in whole blood without making assumptions about their relative individual contribution. The assay described by our group uses small volumes of whole blood and has already been employed in studies of adults and children in TB-endemic settings. We have shown immunogenicity of the BCG vaccine, increased growth of mycobacteria in HIV-positive patients, as well as the effect of anti-retroviral therapy and Vitamin D on mycobacterial survival in vitro. Here we summarise the methodology, and present our reproducibility data using this relatively simple, low-cost and field-friendly model.
Note: Definitions/Abbreviations
BCG lux = M. bovis BCG, Montreal strain, transformed with shuttle plasmid pSMT1 carrying the luxAB genes from Vibrio harveyi, under the control of the mycobacterial GroEL (hsp60) promoter. 
CFU = Colony Forming Unit (a measure of mycobacterial viability).

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb BCG lux/M.Tb lux

We describe an alternative approach to the enumeration of mycobacteria in vitro, which uses reporter-gene tagged mycobacteria instead of colony-forming units (CFU). &#x201C;Survival&#x201D; of organisms as well as host response-markers are measured simultaneously, providing a low-cost, versatile and functional system for studies of host/pathogen interactions in the context of tuberculosis.

一个功能全血含量测量分枝杆菌的生存能力，记者基因标记卡介苗或M. TB（卡介苗勒克斯 / M. TB勒克斯）

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal ...

A Visual Assay to Monitor T6SS-mediated Bacterial Competition

Type VI secretion systems (T6SSs) are molecular nanomachines allowing Gram-negative bacteria to transport and inject proteins into a wide variety of target cells1,2. The T6SS is composed of 13 core components and displays structural similarities with the tail-tube of bacteriophages3. The phage uses a tube and a puncturing device to penetrate the cell envelope of target bacteria and inject DNA. It is proposed that the T6SS is an inverted bacteriophage device creating a specific path in the bacterial cell envelope to drive effectors and toxins to the surface. The process could be taken further and the T6SS device could perforate other cells with which the bacterium is in contact, thus injecting the effectors into these targets. The tail tube and puncturing device parts of the T6SS are made with Hcp and VgrG proteins, respectively4,5.
The versatility of the T6SS has been demonstrated through studies using various bacterial pathogens. The Vibrio cholerae T6SS can remodel the cytoskeleton of eukaryotic host cells by injecting an "evolved" VgrG carrying a C-terminal actin cross-linking domain6,7. Another striking example was recently documented using Pseudomonas aeruginosa which is able to target and kill bacteria in a T6SS-dependent manner, therefore promoting the establishment of bacteria in specific microbial niches and competitive environment8,9,10.
In the latter case, three T6SS-secreted proteins, namely Tse1, Tse2 and Tse3 have been identified as the toxins injected in the target bacteria (Figure 1). The donor cell is protected from the deleterious effect of these effectors via an anti-toxin mechanism, mediated by the Tsi1, Tsi2 and Tsi3 immunity proteins8,9,10. This antimicrobial activity can be monitored when T6SS-proficient bacteria are co-cultivated on solid surfaces in competition with other bacterial species or with T6SS-inactive bacteria of the same species8,11,12,13.
The data available emphasized a numerical approach to the bacterial competition assay, including time-consuming CFU counting that depends greatly on antibiotic makers. In the case of antibiotic resistant strains like P. aeruginosa, these methods can be inappropriate. Moreover, with the identification of about 200 different T6SS loci in more than 100 bacterial genomes14, a convenient screening tool is highly desirable. We developed an assay that is easy to use and requires standard laboratory material and reagents. The method offers a rapid and qualitative technique to monitor the T6SS-dependent bactericidal/bacteriostasis activity by using a reporter strain as a prey (in this case Escherichia coli DH5&alpha;) allowing a-complementation of the lacZ gene. Overall, this method is graphic and allows rapid identification of T6SS-related phenotypes on agar plates. This experimental protocol may be adapted to other strains or bacterial species taking into account specific conditions such as growth media, temperature or time of contact.

We describe a qualitative assay to monitor bacterial competition mediated by the Pseudomonas aeruginosa type VI secretion system (T6SS). The assay relies on the survival/killing of Escherichia coli target cells carrying a lacZ-reporter. This technique is adjustable to assess the bactericidal/bacteriostasis activity of T6SS-proficient microorganisms.

的视觉检测，以监测T6SS介导的细菌竞争

Type VI secretion systems (T6SSs) are molecular  nanomachines allowing Gram-negative bacteria to transport and inject proteins  into a wide variety of ...

Using Click Chemistry to Measure the Effect of Viral Infection on Host-Cell RNA Synthesis

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, it is therefore important to have a quick and reliable way of measuring transcriptional activity in infected cells. Traditionally, transcription has been measured either by incorporation of radioactive nucleosides such as 3H-uridine followed by detection via autoradiography or scintillation counting, or incorporation of halogenated uridine analogs such as 5-bromouridine (BrU) followed by detection via immunostaining. The use of radioactive isotopes, however, requires specialized equipment and is not feasible in a number of laboratory settings, while the detection of BrU can be cumbersome and may suffer from low sensitivity.
The recently developed click chemistry, which involves a copper-catalyzed triazole formation from an azide and an alkyne, now provides a rapid and highly sensitive alternative to these two methods. Click chemistry is a two step process in which nascent RNA is first labeled by incorporation of the uridine analog 5-ethynyluridine (EU), followed by detection of the label with a fluorescent azide. These azides are available as several different fluorophores, allowing for a wide range of options for visualization.
This protocol describes a method to measure transcriptional suppression in cells infected with the Rift Valley fever virus (RVFV) strain MP-12 using click chemistry. Concurrently, expression of viral proteins in these cells is determined by classical intracellular immunostaining. Steps 1 through 4 detail a method to visualize transcriptional suppression via fluorescence microscopy, while steps 5 through 8 detail a method to quantify transcriptional suppression via flow cytometry. This protocol is easily adaptable for use with other viruses.

This method describes the use of click chemistry to measure changes in host cell transcription after infection with the Rift Valley fever virus (RVFV) strain MP-12. Results can be visualized qualitatively via fluorescence microscopy or obtained quantitatively through flow cytometry. This method is adaptable for use with other viruses.

使用点击化学测量的影响，病毒感染宿主细胞RNA合成

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, ...

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a prerequisite for pneumococcal infections such as pneumonia and otitis media. In vitro adherence assays can be used to study the attachment of pneumococci to epithelial cell monolayers and to investigate potential interventions, such as the use of probiotics, to inhibit pneumococcal&#160;colonization.&#160;The protocol described here is used to investigate the effects of the probiotic Streptococcus salivarius on the adherence of pneumococci to the human epithelial cell line CCL-23 (sometimes referred to as HEp-2 cells). The assay involves three main steps: 1) preparation of epithelial and bacterial cells, 2) addition of bacteria to epithelial cell monolayers, and 3) detection of adherent pneumococci by viable counts (serial dilution and plating) or quantitative real-time PCR (qPCR). This technique is relatively straightforward and does not require specialized equipment other than a tissue culture setup. The assay can be used to test other probiotic species and/or potential inhibitors of pneumococcal colonization and can be easily modified to address other scientific questions regarding pneumococcal adherence and invasion.

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

In vitro adherence assays can be used to study the attachment of Streptococcus pneumoniae to epithelial cell monolayers and to investigate potential interventions such as the use of probiotics for inhibiting pneumococcal colonization.

使用一个调查益生素对肺炎球菌定植的影响<em&gt;体外</em&gt;粘附试验

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a ...

Cell-based Flow Cytometry Assay to Measure Cytotoxic Activity

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells to kill CD4+ T cells loaded with their cognate peptide. Target CD4+ T cells are divided into two populations, labeled with two different concentrations of CFSE. One population is pulsed with the peptide of interest (CFSE-low) while the other remains un-pulsed (CFSE-high). Pulsed and un-pulsed CD4+ T cells are mixed at an equal ratio and incubated with an increasing number of purified CD8+ T cells. The specific killing of autologous target CD4+ T cells is analyzed by flow cytometry after coculture with CD8+ T cells containing the antigen-specific effector CD8+ T cells detected by peptide/MHCI tetramer staining. The specific lysis of target CD4+ T cells measured at different effector versus target ratios, allows for the calculation of lytic units, LU30/106 cells. This simple and straightforward assay allows for the accurate measurement of the intrinsic capacity of CD8+ T cells to kill target CD4+ T cells.

This protocol describes a sensitive, cell-based cytotoxicity assay. By enumerating the decrease in frequency of live target CD4+ T cells in the presence of an increasing number of effector CD8+ T cells, this assay allows for the direct assessment of cytolytic activity of antigen-specific CD8+ T cells.

基于细胞的流式细胞仪检测，以测量细胞毒活性

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells ...

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal epidemiology, capsular serotyping can provide useful information for vaccine efficacy and impact studies.&#160;The Quellung reaction is the gold standard method for pneumococcal capsular serotyping. The method involves testing a pneumococcal cell suspension with pooled and specific antisera directed against the capsular polysaccharide. The antigen-antibody reactions are observed microscopically. The protocol has three main steps: 1) preparation of a bacterial cell suspension, 2) mixing of cells and antisera on a glass slide, and 3) reading the Quellung reaction using a microscope. The Quellung reaction is reasonably simple to perform and can be applied wherever a suitable microscope and antisera are available.

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

The Quellung reaction is the gold standard technique for serotyping Streptococcus pneumoniae. This technique utilizes a microscope and specific pneumococcal antisera and is commonly used in reference and research laboratories worldwide.

荚膜血清型<em&gt;肺炎链球菌</em&gt;使用荚膜肿胀反应

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal ...

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major cause of morbidity and mortality world-wide. Current vaccines target the pneumococcal capsule, and there are over 90 capsular serotypes. Serotyping pneumococcal isolates is therefore important for assessing the impact of vaccination programs and for epidemiological purposes. The World Health Organization has recommended latex agglutination as an alternative method to the &#8216;gold standard&#8217; Quellung test for serotyping pneumococci. Latex agglutination is a relatively simple, quick and inexpensive method; and is therefore suitable for resource-poor settings as well as laboratories with high-volume workloads. Latex agglutination reagents can be prepared in-house utilizing commercially-sourced antibodies that are passively attached to latex particles. This manuscript describes a method of production and quality control of latex agglutination reagents, and details a sequential testing approach which is time- and cost-effective. 
This method of production and quality control may also be suitable for other testing purposes.

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination testing is a simple, rapid and inexpensive method for serotyping Streptococcus pneumoniae, and has also been widely applied in diagnostic microbiology. This manuscript describes the in-house production of latex agglutination reagents, quality control procedures and the application of this technique to pneumococcal serotyping.

荚膜血清型<em&gt;肺炎链球菌</em&gt;乳胶凝集

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major ...

Methods to Inhibit Bacterial Pyomelanin Production and Determine the Corresponding Increase in Sensitivity to Oxidative Stress

Pyomelanin is an extracellular red-brown pigment produced by several bacterial and fungal species. This pigment is derived from the tyrosine catabolism pathway and contributes to increased oxidative stress resistance. Pyomelanin production in Pseudomonas aeruginosa is reduced in a dose dependent manner through treatment with 2-[2-nitro-4-(trifluoromethyl)benzoyl]-1,3-cyclohexanedione (NTBC). We describe a titration method using multiple concentrations of NTBC to determine the concentration of drug that will reduce or abolish pyomelanin production in bacteria. The titration method has an easily quantifiable outcome, a visible reduction in pigment production with increasing drug concentrations. We also describe a microtiter plate method to assay antibiotic minimum inhibitory concentration (MIC) in bacteria. This method uses a minimum of resources and can easily be scaled up to test multiple antibiotics in one microtiter plate for one strain of bacteria. The MIC assay can be adapted to test the affects of non-antibiotic compounds on bacterial growth at specific concentrations. Finally, we describe a method for testing bacterial sensitivity to oxidative stress by incorporating H2O2 into agar plates and spotting multiple dilutions of bacteria onto the plates. Sensitivity to oxidative stress is indicated by reductions in colony number and size for the different dilutions on plates containing H2O2 compared to a no H2O2 control. The oxidative stress spot plate assay uses a minimum of resources and low concentrations of H2O2. Importantly, it also has good reproducibility. This spot plate assay could be adapted to test bacterial sensitivity to various compounds by incorporating the compounds in agar plates and characterizing the resulting bacterial growth.

Bacterial pyomelanin production results in increased resistance to oxidative stress and virulence. We report on techniques that can be used to determine inhibition of pyomelanin production and assay the resulting increase in sensitivity to oxidative stress in bacteria, as well as determine antibiotic minimum inhibitory concentration (MIC).

方法来抑制细菌Pyomelanin生产和确定敏感性氧化应激的影响相应增加

Pyomelanin is an extracellular red-brown pigment produced by several bacterial and fungal species. This pigment is derived from the tyrosine catabolism ...

Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds

The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, including work with bacteriophages and bacteriocins, proteinaceous antibacterial agents. This approach is relatively inexpensive, with minimal resource requirements. This technique consists of spotting supernatant from a donor strain (potentially harboring a toxic compound(s)) onto a solidified soft agar overlay that is seeded with a bacterial test strain (potentially sensitive to the toxic compound(s)). We utilized this technique to screen a library of Pseudomonas syringae strains for intraspecific killing. By combining this approach with a precipitation step and targeted gene deletions, multiple toxic compounds produced by the same strain can be differentiated. The two antagonistic agents commonly recovered using this technique are bacteriophages and bacteriocins. These two agents can be differentiated using two simple additional tests. Performing a serial dilution on a supernatant containing bacteriophage will result in individual plaques becoming less in number with greater dilution, whereas serial dilution of a supernatant containing bacteriocin will result a clearing zone that becomes uniformly more turbid with greater dilution. Additionally, a bacteriophage will produce a clearing zone when spotted onto a fresh soft agar overlay seeded with the same strain, whereas a bacteriocin will not produce a clearing zone when transferred to a fresh soft agar lawn, owing to the dilution of the bacteriocin.

We describe a simple method for screening bacterial cultures for the production of compounds inhibitory towards other bacteria.