The work was carried out with financial support from the National Institute of Health and American Lung Association.

1. Growing biofilms of M. tuberculosis in a 250mL screw capped bottle
<ol>
 <li>Media preparation: Dissolve 0.5g of KH2PO4, 0.5g of MgSO4, 4g of L-Asparagine, 2g of Citric acid, 0.05g of Ferric Ammonium Citrate, 60mL of glycerol in 900mL of water. Adjust the pH to 7.0 with NaOH. Autoclave, cool and just prior to starting the experiment, add sterile ZnSO4 to a final concentration of 0.1% w/v. Since mc27000 is a pantothenate auxotroph this strain also requires pantothenic acid at 10&mu;g/mL of final concentration.</li>
</ol>
Note: This is a standard composition of Sauton's media used for M. tuberculosis. However, if required other specialized media can also be used for other mycobacterial species.
<ol start="2">
 <li>Inoculums preparation: Grow M. tuberculosis in 7H9OADC with 0.05% Tween-80 for one week, or OD600 of 0.7 to 1.0. The culture can be directly used as inoculum at a 1:100 dilution.</li>
 <li>Dispense 25mL of Sauton's media to a 250mL screw capped polystyrene bottle (Corning). Add 250&mu;l of the inoculum to the medium, cap the bottle very tightly and place it undisturbed in a humidified 37&deg;C incubator for 3 weeks. Observe the bottle once every day to ensure that there is no contamination.</li>
 <li>At the end of third week, loosen the cap of the bottle to allow further growth of M. tuberculosis at the interface. If the cap is not loosened at this stage then the insufficient oxygen concentration in the container will retard further growth of bacteria.</li>
</ol>

2. Growth of M. tuberculosis biofilms in 12-well plates
<ol>
 <li>Prepare the media and inoculum of mc27000 as described in sections A1 and A2.</li>
 <li>Mix 60mL of media with 600&mu;l of inoculum. Dispense 4.5mL of the mixture into each well of the plate. Cover the plate with lid. Wrap the plate several times with parafilm. Incubate the plate undisturbed in humidified incubator at 37&deg;C for 5 weeks.</li>
</ol>
3. Determining the frequency of drug tolerant persisters in M. tuberculosis biofilms
<ol>
 <li>Grow M. tuberculosis biofilms in a 12-well format as described in section B. This will take a total of about 5-weeks.</li>
 <li>Once the biofilms are matured (after 5 weeks of incubation) inject your choice of antibiotic at desired concentration into the media beneath the biofilms using a microtip in a pipette.</li>
</ol>
Note: The volume of the media beneath the pellicles reduces to about 3.0mL. So investigators should accordingly calculate the amount of drug.
<ol start="3">
 <li>Swirl the plate gently so that the antibiotic is thoroughly diffused in the medium. For statistically significant results, inject the antibiotic in four wells. In parallel, inject the same volume of solvent in which the antibiotic was dissolved in other four wells, and leave the last four wells of the plate untouched. Cover the plate with lid and put fresh layers of parafilm around the plate. Place it back in the incubator for desired time period.</li>
 <li>At the end of the incubation, open the plate and add Tween-80 to the final concentration of 0.1% (volume/volume) in each of the wells. Swirl the whole plate gently for uniform dispersal of the detergent. Incubate the plate at room temperature for 15 minutes. Mix the content of each well with pipette several times so that entire content can be uniformly transferred to a 15mL conical tube.</li>
 <li>Spin down the content of the tube at 4000rpm for 10 minutes at room temperature. Resuspend the pellet in 5mL of fresh wash buffer (PBS with 10% glycerol and 0.05% Tween-80). Repeat the washing three times. Resuspend the pellet in 5mL of wash buffer. Keep it on the rocker for overnight at 4&deg;C.</li>
</ol>
Note: Although low temperature was originally developed for M. smegmatis (to minimize its growth during dispersion) and used for M. tuberculosis as well, the slow growing species can most likely be rocked at room temperature without any impact on result. Rocking at room temperature could be necessary if working in BSL-3 facility.
<ol start="6">
 <li>Prepare a sterile syringe fitted with microtip (2-200&mu;l) by cutting its broad end to the appropriate size, fitting it to the syringe and wrapping it with parafilm. Pass the whole content of the tube through the tip-fitted syringe and collect in a fresh 15mL tubes. Repeat this step 5 to 6 times till you observe a fairly homogenous suspension.</li>
 <li>Prepare serial dilutions of the suspension and plate the dilutions on 7H11OADC plate to determine the number of viable colonies in each well. Incubate the plates for three weeks in 37&deg;C incubator. Determine the frequency of persisters in the biofilm population by calculating the ratio of number of colonies obtained in antibiotic treated to those obtained on solvent treated plates.</li>
</ol>
4. Representative Results
When cultured in a bottle, growth of M. tuberculosis can be seen at the base of the bottle by the end of the first week. By the end of the second week, patchy growth of bacteria on the air-media interface can be seen, although growth at the air-media interface is consistently visible at the end of the third week (Fig. 1A). At this time the attachment of the bacteria to the wall of the container is also observed. From this point onward the growth of the culture primarily occurs on the air-media interface. The liquid beneath the surface growth is clear. Typically, the structure matures by the end of the fifth week (Fig. 1B). If incubation is prolonged, the structures will begin to sink to the bottom of the container. Intriguingly, tightening of the cap until the end of third week is an important step in the process, and for unknown reasons a loose-capped bottle significantly retards initiation of growth on the interface 9.
In the 12-well format, a robust biofilm at the air-media interface is seen in each of the wells at the end of five weeks (Fig 2A). If the plates are not wrapped completely then differential biofilm growth is observed. In the worst case, significant media evaporation can stall the growth of the bacteria (Fig 2B). Thus, wrapping of the plate is necessary both to prevent the evaporation as well as to provide environment for biofilm formation (see previous paragraph).
The number of viable bacilli in biofilms determined with this technique is quite reproducible. Response of M. tuberculosis biofilms varies with the nature of the antibiotics. For a bactericidal antibiotic such as rifampicin, loss of viability follows a biphasic trend 9. A rapid decline in the viability during the first three to four days followed by a persistent phase in which a small percentage of the population remain completely recalcitrant to antibiotics irrespective of the concentration of the antibiotic or the time of exposure. Figure 3 shows the number of viable bacilli in mature biofilms after a 7-day exposure to 50&mu;g/mL (50 times higher than the MIC) of rifampicin.
<img alt="Figure 1A." src="/files/ftp_upload/3820/3820fig1A.jpg" /> 
Figure 1A. Early appearance of M. tuberculosis bacilli on the air-media interface of bacteria after 3 weeks of incubation.
<img alt="Figure 1B." src="/files/ftp_upload/3820/3820fig1B.jpg" /> 
Figure 1B. Matured biofilms of M. tuberculosis on the air-media interface after five weeks of incubation.
<img alt="Figure 2A." src="/files/ftp_upload/3820/3820fig2A.jpg" /> 
Figure 2A. 5-week old biofilms of M. tuberculosis grown in 12-well format.
<img alt="Figure 2B." src="/files/ftp_upload/3820/3820fig2B.jpg" /> 
Figure 2B. A failed attempt to grow M. tuberculosis biofilms in 12-well plate without parafilm.
<img alt="Figure 3." src="/files/ftp_upload/3820/3820fig3.jpg" /> 
Figure 3. A representative plot showing the frequency of drug tolerant persisters in M. tuberculosis biofilms grown in 12-well format and exposed to 50&mu;g/mL of Rifampicin for seven days.

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	<li>Saltini, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemotherapy+and+diagnosis+of+tuberculosis.">Chemotherapy and diagnosis of tuberculosis.</a> Respir. Med. 100, 2085-2097 (2006).</li><li>Hall-Stoodley, L., Stoodley, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilm+formation+and+dispersal+and+the+transmission+of+human+pathogens.">Biofilm formation and dispersal and the transmission of human pathogens.</a> Trends Microbiol. 13, 7-10 (2005).</li><li>Costerton, J. W., Stewart, P. S., Greenberg, E. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+biofilms:+a+common+cause+of+persistent+infections.">Bacterial biofilms: a common cause of persistent infections.</a> Science. 284, 1318-1322 (1999).</li><li>Blankenship, J. R., Mitchell, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+build+a+biofilm:+a+fungal+perspective.">How to build a biofilm: a fungal perspective.</a> Curr Opin Microbiol. 9, 588-594 (2006).</li><li>Henke, J. M., Bassler, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+social+engagements.">Bacterial social engagements.</a> Trends Cell Biol. 14, 648-656 (2004).</li><li>Kolter, R., Losick, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One+for+all+and+all+for+one.">One for all and all for one.</a> Science. 280, 226-227 (1998).</li><li>Branda, S. S., Vik, S., Friedman, L., Kolter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilms:+the+matrix+revisited.">Biofilms: the matrix revisited.</a> Trends Microbiol. 13, 20-26 (2005).</li><li>Ojha, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GroEL1:+a+dedicated+chaperone+involved+in+mycolic+acid+biosynthesis+during+biofilm+formation+in+mycobacteria.">GroEL1: a dedicated chaperone involved in mycolic acid biosynthesis during biofilm formation in mycobacteria.</a> Cell. 123, 861-873 (2005).</li><li>Ojha, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+Mycobacterium+tuberculosis+biofilms+containing+free+mycolic+acids+and+harbouring+drug-tolerant+bacteria.">Growth of Mycobacterium tuberculosis biofilms containing free mycolic acids and harbouring drug-tolerant bacteria.</a> Mol. Microbiol. 69, 164-174 (2008).</li><li>Ojha, A. K., Trivelli, X., Guerardel, Y., Kremer, L., Hatfull, G. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzymatic+hydrolysis+of+trehalose+dimycolate+releases+free+mycolic+acids+during+mycobacterial+growth+in+biofilms.">Enzymatic hydrolysis of trehalose dimycolate releases free mycolic acids during mycobacterial growth in biofilms.</a> J. Biol. Chem. 285, 17380-17389 (2010).</li><li>Dye, C., Lonnroth, K., Jaramillo, E., Williams, B. G., Raviglione, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trends+in+tuberculosis+incidence+and+their+determinants+in+134+countries.">Trends in tuberculosis incidence and their determinants in 134 countries.</a> Bull World Health Organ. 87, 683-691 (2009).</li><li>Jindani, A., Dore, C. J., Mitchison, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bactericidal+and+sterilizing+activities+of+antituberculosis+drugs+during+the+first+14+days.">Bactericidal and sterilizing activities of antituberculosis drugs during the first 14 days.</a> Am. J. Respir. Crit. Care Med. 167, 1348-1354 (2003).</li><li>Carter, G., Wu, M., Drummond, D. C., Bermudez, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+biofilm+formation+by+clinical+isolates+of+Mycobacterium+avium.">Characterization of biofilm formation by clinical isolates of Mycobacterium avium.</a> J. Med. Microbiol. 52, 747-752 (2003).</li><li>Hall-Stoodley, L., Lappin-Scott, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilm+formation+by+the+rapidly+growing+mycobacterial+species+Mycobacterium+fortuitum.">Biofilm formation by the rapidly growing mycobacterial species Mycobacterium fortuitum.</a> FEMS Microbiol. Lett. 168, 77-84 (1998).</li><li>Alibaud, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-dependent+regulation+of+mycolic+acid+cyclopropanation+in+saprophytic+mycobacteria:+role+of+the+Mycobacterium+smegmatis+1351+gene+(MSMEG_1351)+in+CIS-cyclopropanation+of+alpha-mycolates.">Temperature-dependent regulation of mycolic acid cyclopropanation in saprophytic mycobacteria: role of the Mycobacterium smegmatis 1351 gene (MSMEG_1351) in CIS-cyclopropanation of alpha-mycolates.</a> J. Biol. Chem. 285, 21698-21707 (2010).</li></ol>

We have nothing to disclose.

Tuberculosis (TB), caused by the infection of Mycobacterium tuberculosis, remains a major threat to the global public health. Nearly one third of the world's population is estimated to be asymptomatically infected by the pathogen, about 9 million new cases show up in clinic every year with symptoms of active TB and about 1.7 million die of the infection every year 11. The huge burden of the disease is primarily contributed by lack of a vaccine and a highly complicated chemotherapy that involves a mult...

<table border="1">
	<tbody>
		<tr>
			<td>Equipment and supplies</td>
			<td>SUPPLIER</td>
			<td>CATALOG NUMBER</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>VWR</td>
			<td>Model # 1923/25</td>
		</tr>
		<tr>
			<td>Polystyrene culture bottles</td>
			<td>Fisher Scientific</td>
			<td>03-374-300</td>
		</tr>
		<tr>
			<td>12-well tissue culture plate</td>
			<td>VWR</td>
			<td>62406-165</td>
		</tr>
		<tr>
			<td>50-mL conical tubes</td>
			<td>VWR</td>
			<td>89039-660</td>
		</tr>
		<tr>
			<td>Rocker</td>
			<td>Thermo Scientific</td>
			<td>57019-662</td>
		</tr>
		<tr>
			<td>Chromatographic refrigerator</td>
			<td>VWR</td>
			<td>55702-520</td>
		</tr>
		<tr>
			<td>petri dish</td>
			<td>VWR</td>
			<td>25384-342</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>REAGENT</td>
			<td>SUPPLIER</td>
			<td>CATALOG NUMBER</td>
		</tr>
		<tr>
			<td>KH2PO4 (monobasic)</td>
			<td>EMD</td>
			<td>PX1565-1</td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Fisher</td>
			<td>M65-500</td>
		</tr>
		<tr>
			<td>L-asparagine</td>
			<td>Sigma</td>
			<td>A4284-100G</td>
		</tr>
		<tr>
			<td>citric acid</td>
			<td>Sigma</td>
			<td>C1857-100G</td>
		</tr>
		<tr>
			<td>ferric ammonium citrate</td>
			<td>Sigma</td>
			<td>F5879-100G</td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>EMD</td>
			<td>GX0185-5</td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Sigma</td>
			<td>S8045-500G</td>
		</tr>
		<tr>
			<td>ZnSO4</td>
			<td>Sigma</td>
			<td>Z4750-500G</td>
		</tr>
		<tr>
			<td>D-pantothenic acid</td>
			<td>Sigma</td>
			<td>P2250-25G</td>
		</tr>
		<tr>
			<td>Difco Middlebrook 7H9 Broth</td>
			<td>Becton Dickinson</td>
			<td>271310</td>
		</tr>
		<tr>
			<td>Middlebrook OADC Enrichment</td>
			<td>BBL</td>
			<td>212351</td>
		</tr>
		<tr>
			<td>Tween-80</td>
			<td>Fisher</td>
			<td>T164-500</td>
		</tr>
		<tr>
			<td>250mL storage bottle</td>
			<td>Corning</td>
			<td>430281</td>
		</tr>
		<tr>
			<td>12 well plates</td>
			<td>Falcon (BD)</td>
			<td>353043</td>
		</tr>
		<tr>
			<td>rifampicin</td>
			<td>Sigma</td>
			<td>R3501-1G</td>
		</tr>
		<tr>
			<td>methanol</td>
			<td>J.T. Baker</td>
			<td>9070-05</td>
		</tr>
		<tr>
			<td>10mlLsyringe</td>
			<td>Becton Dickinson</td>
			<td>301604</td>
		</tr>
		<tr>
			<td>1-200&mu;L pipet tips</td>
			<td>VWR</td>
			<td>89079-458</td>
		</tr>
		<tr>
			<td>parafilm M</td>
			<td>VWR</td>
			<td>PM-996</td>
		</tr>
		<tr>
			<td>15mL centrifuge tube</td>
			<td>Greiner Bio-One</td>
			<td>188-285</td>
		</tr>
		<tr>
			<td>Difco Mycobacteria 7H11 Agar</td>
			<td>Becton Dickinson</td>
			<td>283810</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Fisher</td>
			<td>BP358-1</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P9333-500G</td>
		</tr>
		<tr>
			<td>Na2HPO4 (dibasic)</td>
			<td>Sigma</td>
			<td>S0876-500G</td>
		</tr>
	</tbody>
</table>

growth of mycobacterium tuberculosis biofilms

Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, has an extraordinary ability to survive against environmental stresses including antibiotics. Although stress tolerance of M. tuberculosis is one of the likely contributors to the 6-month long chemotherapy of tuberculosis 1, the molecular mechanisms underlying this characteristic phenotype of the pathogen remain unclear. Many microbial species have evolved to survive in stressful environments by self-assembling in highly organized, surface attached, and matrix encapsulated structures called biofilms 2-4. Growth in communities appears to be a preferred survival strategy of microbes, and is achieved through genetic components that regulate surface attachment, intercellular communications, and synthesis of extracellular polymeric substances (EPS) 5,6. The tolerance to environmental stress is likely facilitated by EPS, and perhaps by the physiological adaptation of individual bacilli to heterogeneous microenvironments within the complex architecture of biofilms 7.
In a series of recent papers we established that M. tuberculosis and Mycobacterium smegmatis have a strong propensity to grow in organized multicellular structures, called biofilms, which can tolerate more than 50 times the minimal inhibitory concentrations of the anti-tuberculosis drugs isoniazid and rifampicin 8-10. M. tuberculosis, however, intriguingly requires specific conditions to form mature biofilms, in particular 9:1 ratio of headspace: media as well as limited exchange of air with the atmosphere 9. Requirements of specialized environmental conditions could possibly be linked to the fact that M. tuberculosis is an obligate human pathogen and thus has adapted to tissue environments. In this publication we demonstrate methods for culturing M. tuberculosis biofilms in a bottle and a 12-well plate format, which is convenient for bacteriological as well as genetic studies. We have described the protocol for an attenuated strain of M. tuberculosis, mc27000, with deletion in the two loci, panCD and RD1, that are critical for in vivo growth of the pathogen 9. This strain can be safely used in a BSL-2 containment for understanding the basic biology of the tuberculosis pathogen thus avoiding the requirement of an expensive BSL-3 facility. The method can be extended, with appropriate modification in media, to grow biofilm of other culturable mycobacterial species.
Overall, a uniform protocol of culturing mycobacterial biofilms will help the investigators interested in studying the basic resilient characteristics of mycobacteria. In addition, a clear and concise method of growing mycobacterial biofilms will also help the clinical and pharmaceutical investigators to test the efficacy of a potential drug.

Watch this Scientific Journal Video about Growth of Mycobacterium tuberculosis Biofilms at JoVE.com

Growth of Mycobacterium tuberculosis Biofilms

Mycobacterium tuberculosis forms drug tolerant biofilms when cultured in certain conditions. Here we describe methods for culturing M. tuberculosis biofilms and determining the frequency of drug tolerant persisters. These protocols will be useful for further studies into the mechanisms of drug tolerance in M. tuberculosis.

Growth of Mycobacterium tuberculosis Biofilms

Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, has an extraordinary ability to survive against environmental stresses including ...

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Immunology and Infection

23.6K Views.  University of Pittsburgh. Mycobacterium tuberculosis forms drug tolerant biofilms when cultured in certain conditions. Here we describe methods for culturing M. tuberculosis biofilms and determining the frequency of drug tolerant persisters. These protocols will be useful for further studies into the mechanisms of drug tolerance in M. tuberculosis.

Video: Growth of Mycobacterium tuberculosis Biofilms

Antimicrobial Susceptibility Testing of Mycobacterium Tuberculosis Complex for First and Second Line Drugs by Broth Dilution in a Microtiter Plate Format

The rapid detection of antimicrobial resistance is important in the effort to control the increase in resistant Mycobacterium 
tuberculosis (Mtb). Antimicrobial susceptibility testing (AST) of Mtb has traditionally been performed by the agar method of proportion or by 
macrobroth testing on an instrument such as the BACTEC (Becton Dickinson, Sparks, MD), VersaTREK (TREK Diagnostics, Cleveland, OH) or BacT/ALERT (bioM&eacute;rieux, Hazelwood, MO). The agar proportion method, while considered the &#x201C;gold&#x201D; standard of AST, is labor intensive and requires calculation of resistance by performing colony counts on drug-containing agar as compared to drug-free agar. If there is &ge;1% growth on the drug-containing medium as compared to drug-free medium, the organism is considered resistant to that drug. The macrobroth methods require instrumentation and test break point ("critical") drug concentrations for the first line drugs (isoniazid, ethambutol, rifampin, and pyrazinamide). The method described here is commercially available in a 96 well microtiter plate format [MYCOTB (TREK Diagnostics)] and contains increasing concentrations of 12 antimicrobials used for treatment of tuberculosis including both first (isoniazid, rifampin, ethambutol) and second line drugs (amikacin, cycloserine, ethionamide, kanamycin, moxifloxacin, ofloxacin, para-aminosalicylic acid, rifabutin, and streptomycin). Pyrazinamide, a first line drug, is not included in the microtiter plate due to its need for acidic test conditions. Advantages of the microtiter system include both ease of set up and faster turn around time (14 days) compared with traditional agar proportion (21 days). In addition, the plate can be set up from inoculum prepared using either broth or solid medium. Since the microtiter plate format is new and since Mtb presents unique safety challenges in the laboratory, this protocol will describe how to safely setup, incubate and read the microtiter plate.

Antimicrobial susceptibility testing of Mycobacterium tuberculosis is challenging but critical for patient care. This microtiter plate format offers testing of 12 antimycobacterial drugs and provides minimum inhibitory concentration (MIC) values, which will aid in appropriate treatment.

The rapid detection of antimicrobial resistance is important in the effort to control the increase in resistant Mycobacterium 
tuberculosis (Mtb). ...

Sample Preparation of Mycobacterium tuberculosis Extracts for Nuclear Magnetic Resonance Metabolomic Studies

Mycobacterium tuberculosis is a major cause of mortality in human beings on a global scale. The emergence of both multi- (MDR) and extensively-(XDR) drug-resistant strains threatens to derail current disease control efforts. Thus, there is an urgent need to develop drugs and vaccines that are more effective than those currently available. The genome of M. tuberculosis has been known for more than 10 years, yet there are important gaps in our knowledge of gene function and essentiality. Many studies have since used gene expression analysis at both the transcriptomic and proteomic levels to determine the effects of drugs, oxidants, and growth conditions on the global patterns of gene expression. Ultimately, the final response of these changes is reflected in the metabolic composition of the bacterium including a few thousand small molecular weight chemicals. Comparing the metabolic profiles of wild type and mutant strains, either untreated or treated with a particular drug, can effectively allow target identification and may lead to the development of novel inhibitors with anti-tubercular activity. Likewise, the effects of two or more conditions on the metabolome can also be assessed. Nuclear magnetic resonance (NMR) is a powerful technology that is used to identify and quantify metabolic intermediates. In this protocol, procedures for the preparation of M. tuberculosis cell extracts for NMR metabolomic analysis are described. Cell cultures are grown under appropriate conditions and required Biosafety Level 3 containment,1 harvested, and subjected to mechanical lysis while maintaining cold temperatures to maximize preservation of metabolites. Cell lysates are recovered, filtered sterilized, and stored at ultra-low temperatures. Aliquots from these cell extracts are plated on Middlebrook 7H9 agar for colony-forming units to verify absence of viable cells. Upon two months of incubation at 37 &deg;C, if no viable colonies are observed, samples are removed from the containment facility for downstream processing. Extracts are lyophilized, resuspended in deuterated buffer and injected in the NMR instrument, capturing spectroscopic data that is then subjected to statistical analysis. The procedures described can be applied for both one-dimensional (1D) 1H NMR and two-dimensional (2D) 1H-13C NMR analyses. This methodology provides more reliable small molecular weight metabolite identification and more reliable and sensitive quantitative analyses of cell extract metabolic compositions than chromatographic methods. Variations of the procedure described following the cell lysis step can also be adapted for parallel proteomic analysis.

Sample Preparation of Mycobacterium tuberculosis Extracts for Nuclear Magnetic Resonance Metabolomic Studies

The metabolomic profile of Mycobacterium tuberculosis is determined after growth in broth cultures. Conditions can be varied to test the effects of nutritional supplements, oxidants, and anti-tuberculosis agents on the metabolic profile of this microorganism. Procedure for extract preparation is applicable for both 1D 1H and 2D 1H-13C NMR analyses.

Mycobacterium tuberculosis is a major cause of mortality in human beings on a global scale. The emergence of both multi- (MDR) and extensively-(XDR) ...

An Experimental Model to Study Tuberculosis-Malaria Coinfection upon Natural Transmission of Mycobacterium tuberculosis and Plasmodium berghei

Coinfections naturally occur due to the geographic overlap of distinct types of pathogenic organisms. Concurrent infections most likely modulate the respective immune response to each single pathogen and may thereby affect pathogenesis and disease outcome. Coinfected patients may also respond differentially to anti-infective interventions. Coinfection between tuberculosis as caused by mycobacteria and the malaria parasite Plasmodium, both of which are coendemic in many parts of sub-Saharan Africa, has not been studied in detail. In order to approach the challenging but scientifically and clinically highly relevant question how malaria-tuberculosis coinfection modulate host immunity and the course of each disease, we established an experimental mouse model that allows us to dissect the elicited immune responses to both pathogens in the coinfected host. Of note, in order to most precisely mimic naturally acquired human infections, we perform experimental infections of mice with both pathogens by their natural routes of infection, i.e. aerosol and mosquito bite, respectively.

An Experimental Model to Study Tuberculosis-Malaria Coinfection upon Natural Transmission of Mycobacterium tuberculosis and Plasmodium berghei

Tuberculosis and malaria are two of the most prevalent infections in humans and major causes of morbidity and mortality in impoverished populations in the tropics. We established an experimental model system to study outcome of malaria-tuberculosis coinfection in mice after challenge with both pathogens via their natural route of infection.

Coinfections naturally occur due to the geographic overlap of distinct types of pathogenic organisms. Concurrent infections most likely modulate the ...

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 ...

A Novel Microdissection Approach to Recovering Mycobacterium tuberculosis Specific Transcripts from Formalin Fixed Paraffin Embedded Lung Granulomas

Microdissection has been used for the examination of tissues at DNA, RNA, and protein levels for over a decade. Laser capture microscopy (LCM) is the most common microdissection technique used today. In this technique, a laser is used to focally melt a thermoplastic membrane that overlies a dehydrated tissue section1. The tissue section composite is then lifted and separated from the membrane. Although this technique can be used successfully for tissue examination, it is time consuming and expensive. Furthermore, the successful completion of procedures using this technique requires the use of a laser, thus limiting its use. A new more affordable and practical microdissection approach called mesodissection is a possible solution to the pitfalls of LCM. This technique employs the MESO-1/MeSectr system to mill the desired tissue from a slide mounted tissue sample while concurrently dispensing and aspirating fluid to recover the desired tissue sample into a consumable mill bit. Before the dissection process begins, the user aligns the formalin fixed paraffin embedded (FFPE) slide with a hematoxylin and eosin stained (H&#38;E) reference slide. Thereafter, the operator annotates the desired dissection area and proceeds to dissect the appropriate segment. The program generates an archived image of the dissection. The main advantage of mesodissection is the short duration needed to dissect a slide, taking an average of ten minutes from set up to sample generation in this experiment. Additionally, the system is significantly more cost effective and user friendly. A slight disadvantage is that it is not as precise as laser capture microscopy. In this article we demonstrate how mesodissection can be used to extract RNA from slides from FFPE granulomas caused by Mycobacterium tuberculosis (Mtb).

A Novel Microdissection Approach to Recovering Mycobacterium tuberculosis Specific Transcripts from Formalin Fixed Paraffin Embedded Lung Granulomas

Microdissection has been extensively employed for the examination of DNA, RNA, and protein within tissue. Laser capture microscopy (LCM) is the most commonly used method, but a new milling technique, mesodissection, is recently available. We demonstrate RNA extraction from mesodissected formalin fixed paraffin embedded tissue slides of Mycobacterium tuberculosis granulomas.

Microdissection has been used for the examination of tissues at DNA, RNA, and protein levels for over a decade. Laser capture microscopy (LCM) is the most ...

A 3D Human Lung Tissue Model for Functional Studies on Mycobacterium tuberculosis Infection

Tuberculosis (TB) still holds a major threat to the health of people worldwide, and there is a need for cost-efficient but reliable models to help us understand the disease mechanisms and advance the discoveries of new treatment options. In vitro cell cultures of monolayers or co-cultures lack the three-dimensional (3D) environment and tissue responses. Herein, we describe an innovative in vitro model of a human lung tissue, which holds promise to be an effective tool for studying the complex events that occur during infection with Mycobacterium tuberculosis (M. tuberculosis). The 3D tissue model consists of tissue-specific epithelial cells and fibroblasts, which are cultured in a matrix of collagen on top of a porous membrane. Upon air exposure, the epithelial cells stratify and secrete mucus at the apical side. By introducing human primary macrophages infected with M. tuberculosis to the tissue model, we have shown that immune cells migrate into the infected-tissue and form early stages of TB granuloma. These structures recapitulate the distinct feature of human TB, the granuloma, which is fundamentally different or not commonly observed in widely used experimental animal models. This organotypic culture method enables the 3D visualization and robust quantitative analysis that provides pivotal information on spatial and temporal features of host cell-pathogen interactions. Taken together, the lung tissue model provides a physiologically relevant tissue micro-environment for studies on TB. Thus, the lung tissue model has potential implications for both basic mechanistic and applied studies. Importantly, the model allows addition or manipulation of individual cell types, which thereby widens its use for modelling a variety of infectious diseases that affect the lungs.

A 3D Human Lung Tissue Model for Functional Studies on Mycobacterium tuberculosis Infection

Human tuberculosis infection is a complex process, which is difficult to model in vitro. Here we describe a novel 3D human lung tissue model that recapitulates the dynamics that occur during infection, including the migration of immune cells and early granuloma formation in a physiological environment.

Tuberculosis (TB) still holds a major threat to the health of people worldwide, and there is a need for cost-efficient but reliable models to help us ...

Ratiometric Imaging of Extracellular pH in Dental Biofilms

The pH in bacterial biofilms on teeth is of central importance for dental caries, a disease with a high worldwide prevalence. Nutrients and metabolites are not distributed evenly in dental biofilms. A complex interplay of sorption to and reaction with organic matter in the biofilm reduces the diffusion paths of solutes and creates steep gradients of reactive molecules, including organic acids, across the biofilm. Quantitative fluorescent microscopic methods, such as fluorescence life time imaging or pH ratiometry, can be employed to visualize pH in different microenvironments of dental biofilms. pH ratiometry exploits a pH-dependent shift in the fluorescent emission of pH-sensitive dyes. Calculation of the emission ratio at two different wavelengths allows determining local pH in microscopic images, irrespective of the concentration of the dye. Contrary to microelectrodes the technique allows monitoring both vertical and horizontal pH gradients in real-time without mechanically disturbing the biofilm. However, care must be taken to differentiate accurately between extra- and intracellular compartments of the biofilm. Here, the ratiometric dye, seminaphthorhodafluor-4F 5-(and-6) carboxylic acid (C-SNARF-4) is employed to monitor extracellular pH in in vivo grown dental biofilms of unknown species composition. Upon exposure to glucose the dye is up-concentrated inside all bacterial cells in the biofilms; it is thus used both as a universal bacterial stain and as a marker of extracellular pH. After confocal microscopic image acquisition, the bacterial biomass is removed from all pictures using digital image analysis software, which permits to exclusively calculate extracellular pH. pH ratiometry with the ratiometric dye is well-suited to study extracellular pH in thin biofilms of up to 75 &#181;m thickness, but is limited to the pH range between 4.5 and 7.0.

A pH-sensitive ratiometric dye is used in combination with confocal laser scanning microscopy and digital image analysis to monitor extracellular pH in dental biofilms in real-time.

The pH in bacterial biofilms on teeth is of central importance for dental caries, a disease with a high worldwide prevalence. Nutrients and metabolites ...

System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. With the increased spread of multi drug-resistant TB (MDR-TB), there is a real urgency to develop new therapeutic strategies against M. tuberculosis infections. Traditionally, compounds are evaluated based on their antibacterial activity under in vitro growth conditions in broth; however, results are often misleading for intracellular pathogens like M. tuberculosis since in-broth phenotypic screening conditions are significantly different from the actual disease conditions within the human body. Screening for inhibitors that work inside macrophages has been traditionally difficult due to the complexity, variability in infection, and slow replication rate of M. tuberculosis. In this study, we report a new approach to rapidly assess the effectiveness of compounds on the viability of M. tuberculosis in a macrophage infection model. Using a combination of a cytotoxicity assay and an in-broth M. tuberculosis viability assay, we were able to create a screening system that generates a comprehensive analysis of compounds of interest. This system is capable of producing quantitative data at a low cost that is within reach of most labs and yet is highly scalable to fit large industrial settings.

System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis

We have developed a modular high-throughput screening system for discovering novel compounds against Mycobacterium tuberculosis, targeting intracellular and in-broth growing bacteria as well as cytotoxicity against the mammalian host cell.

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. With the increased spread ...

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to effectiveness in the clinical setting. This is likely due to a lack of consideration for the physiologically relevant cellular penetration barriers that exist in the infected host. We recently established an alternative infection model that generates large macrophage aggregate structures containing densely packed M. tuberculosis (Mtb) at its core, which was suitable for drug susceptibility testing. This infection model is inexpensive, rapid, and most importantly BSL-2 compatible. Here, we describe the experimental procedures to generate Mtb/macrophage aggregate structures that would produce macrophage-passaged Mtb for drug susceptibility testing. In particular, we demonstrate how this infection system could be directly adapted to the 96-well plate format showing throughput capability for the screening of compound libraries against Mtb. Overall, this assay is a valuable addition to the currently available Mtb drug discovery toolbox due to its simplicity, cost effectiveness, and scalability.

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

New models and assays that would improve the early drug development process for next-generation anti-tuberculosis drugs are highly desirable. Here, we describe a quick, inexpensive, and BSL-2 compatible assay to evaluate drug efficacy against Mycobacterium tuberculosis that can be easily adapted for high-throughput screening.

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to ...

Analysis of 18FDG PET/CT Imaging as a Tool for Studying Mycobacterium tuberculosis Infection and Treatment in Non-human Primates

Mycobacterium tuberculosis remains the number one infectious agent in the world today. With the emergence of antibiotic resistant strains, new clinically relevant methods are needed that evaluate the disease process and screen for potential antibiotic and vaccine treatments. Positron Emission Tomography/Computed Tomography (PET/CT) has been established as a valuable tool for studying a number of afflictions such as cancer, Alzheimer&#39;s disease, and inflammation/infection. Outlined here are a number of strategies that have been employed to evaluate PET/CT images in cynomolgus macaques that are infected intrabronchially with low doses of M. tuberculosis. Through evaluation of lesion size on CT and uptake of 18F-fluorodeoxyglucose (FDG) in lesions and lymph nodes in PET images, these described methods show that PET/CT imaging can predict future development of active versus latent disease and the propensity for reactivation from a latent state of infection. Additionally, by analyzing the overall level of lung inflammation, these methods determine antibiotic efficacy of drugs against M. tuberculosis in the most clinically relevant existing animal model. These image analysis methods are some of the most powerful tools in the arsenal against this disease as not only can they evaluate a number of characteristics of infection and drug treatment, but they are also directly translatable to a clinical setting for use in human studies.

Analysis of 18FDG PET/CT Imaging as a Tool for Studying Mycobacterium tuberculosis Infection and Treatment in Non-human Primates

Here, we present a protocol to describe the analysis of 18F-FDG PET/CT imaging in non-human primates that have been infected with M. tuberculosis to study disease process, drug treatment, and disease reactivation.

Mycobacterium tuberculosis remains the number one infectious agent in the world today. With the emergence of antibiotic resistant strains, new clinically ...