TB acknowledges a research fellowship from Cystic Fibrosis Canada.

Note that Research Ethics Board (REB) is required to collect and store sputum samples from human subjects. These studies were approved by the Hospital for Sick Children REB#1000019444.
1. Preparing CF Sputum Samples
<ol>
	<li>Collect sputum sample from patients during routine visits to the cystic fibrosis clinic and keep on ice.</li>
	<li>Transport sputum sample on ice within the first hour of collection, to the research laboratory, to undergo processing.</li>
</ol>
2. Sputum Processing
<ol>
	<li>Record the volume of the sputum sample obtained. Add phosphate buffered saline (PBS) to 2x the volume of the sample (i.e., 2 parts PBS, 1 part sample).</li>
	<li>Mix the sample well with a transfer pipette. Vortex the sample on the highest setting for 1 min to mix completely.</li>
	<li>Aliquot 1 ml of the above mixture into the appropriate number 1.5 ml microcentrifuge tubes and spin down at 5,000 x g for 20 min at 4 &#176;C.</li>
	<li>Following centrifugation, remove the supernatant and discard the pellet.</li>
	<li>Filter sterilize the supernatant through a 0.22 &#181;m filter and collect in a clean microcentrifuge tube. 
	NOTE: Sterility of filtrate is tested by plating on LB agar and inoculating liquid media.</li>
	<li>Store sputum supernatant at -80 &#176;C for future use. 
	NOTE: Sputum from multiple patients can also be pooled following filtration.</li>
	<li>Prior to use, dilute sputum filtrate 1/10 v/v (100 &#956;l of sputum, 900 &#956;l of media) in desired media. 
	NOTE: Here, standard lysogeny broth (LB) media was used.</li>
</ol>
3. Chambered Coverglass Method for Biofilm Formation
<ol>
	<li>Grow bacterial isolate of interest overnight in desired media at 37 &#176;C with shaking (200 rpm). 
	Note: A number of different bacteria were used, including clinical isolates Pseudomonas aeruginosa, Staphylococcus aureus, Burkholderia cepacia complex and Achromobacter xylosoxidans. Choice of media depends on strains and conditions of interest, however LB media can be used for initial experiments.</li>
	<li>From overnight culture, place 40 &#956;l of culture into 4 ml of fresh media and grow for 3-4 hr at 37 &#176;C with shaking (200 RPM) to obtain a culture with an optical density at 600 nm (OD600) of approximately 0.5-0.6.</li>
	<li>Dilute the culture from step 3.2 to 1/5 in desired media with 10% sputum filtrate or without sputum filtrate (as control). Other concentration of sputum filtrate can be tested (i.e., 50% or 100%).</li>
	<li>Use 200 &#956;l of the dilution to seed wells of slide chambers.</li>
	<li>Allow bacteria to attach for 4 hr at 37 &#176;C without shaking.</li>
	<li>After 4 hr, remove the media and gently wash the biofilm with 1x fresh media. Replace with 200 &#956;l fresh media. 
	NOTE: To study the effects of sputum on the biofilm, the fresh media should contain sputum supernatant.</li>
	<li>Allow biofilms to grow for desired amount of time at 37 &#176;C without shaking, replacing media every 12 hr, without washing until the time for microscopy. 
	NOTE: To study the effect of sputum supernatants on biofilm antibiotic susceptibility, antibiotics are added to the media following 24 hr of biofilm growth and are maintained in the media until staining and imaging of biofilms.</li>
</ol>
4. Staining Biofilms and Confocal Microscopy
<ol>
	<li>Following desired growth time (24-48 hr works best), remove media from chamber wells and gently wash each chamber twice with 300 &#956;l of sterile PBS.</li>
	<li>Prepare staining mixture for biofilm by mixing 1 &#181;l of each dye (provided in the viability kit) for each ml of solution needed. Make dye in water or media solution. 
	NOTE: Water is recommended by the manufacturer.</li>
	<li>Add 200 &#181;l of dye mixture to each well of chambered coverglass and incubate at room temperature, in the dark for 45 min.</li>
	<li>Remove staining mixture from chambers and wash each well with 300 &#956;l of sterile PBS. Remove PBS and replace with fresh water or media.</li>
	<li>Proceed with visualization of biofilms via confocal microscopy.</li>
</ol>
5. Visualizing Biofilms with Confocal Microscopy
<ol>
	<li>Read stained biofilms in chambers immediately after staining (within 1 hr). Minimize delay in visualization of the slides by staining 1 to 2 8-well chambers at a time.</li>
	<li>Perform imaging using confocal microscope with lasers for excitation and filter sets for acquisition. 
	NOTE: Here, the spinning disk confocal system with spectral borealis lasers (Green: 491nm, Red: 561 nm) were used for excitation. Emission filter sets of 515/40 and 624/40 were used to visualize the stains from the biofilm viability kit.</li>
	<li>Take images using a 25X water objective on confocal microscope with camera.</li>
	<li>Use Z-Stacks to model the biofilm. Take images every 0.5-1 &#956;m starting from the first in-focus plane to the last in-focus frame of the biofilm (typically spanning 30-80 &#956;m for 48 hr biofilms)</li>
	<li>Take 3-5 images from each well. 
	NOTE: Thus for an 8 well chambered coverglass, 24-40 images will be generated.</li>
	<li>Save images for analysis. 
	NOTE: Images should be saved as OME-TIFF files to be analyzed using COMSTAT18,19. Instructions for biofilm image analysis can be found at http://www.comstat.dk/. Once images are imported, parameters such as average thickness, biomass and surface coverage for each channel (red and green) can be analyzed.</li>
</ol>

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	<li>Beaudoin, T., Waters, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infections+with+biofilm+formation:+selection+of+antimicrobials+and+role+of+prolonged+antibiotic+therapy.">Infections with biofilm formation: selection of antimicrobials and role of prolonged antibiotic therapy.</a> Pediatr.Infect.Dis.J. , (2016).</li><li>Donlan, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilms:+microbial+life+on+surfaces.">Biofilms: microbial life on surfaces.</a> Emerg.Infect.Dis. 8 (9), 881-890 (2002).</li><li>Hobley, L., Harkins, C., MacPhee, C. E., Stanley-Wall, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Giving+structure+to+the+biofilm+matrix:+an+overview+of+individual+strategies+and+emerging+common+themes.">Giving structure to the biofilm matrix: an overview of individual strategies and emerging common themes.</a> FEMS Microbiol.Rev. 39 (5), 649-669 (2015).</li><li>Katharios-Lanwermeyer, S., Xi, C., Jakubovics, N. S., Rickard, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mini-review:+Microbial+coaggregation:+ubiquity+and+implications+for+biofilm+development.">Mini-review: Microbial coaggregation: ubiquity and implications for biofilm development.</a> Biofouling. 30 (10), 1235-1251 (2014).</li><li>Donlan, R. M. <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:+a+clinically+relevant+microbiological+process.">Biofilm formation: a clinically relevant microbiological process.</a> Clin.Infect.Dis. 33 (8), 1387-1392 (2001).</li><li>Bjarnsholt, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+in+vivo+biofilm.">The in vivo biofilm.</a> Trends Microbiol. 21 (9), 466-474 (2013).</li><li>Mah, T. F., Pitts, B., Pellock, B., Walker, G. C., Stewart, P. S., O'Toole, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+genetic+basis+for+Pseudomonas+aeruginosa+biofilm+antibiotic+resistance.">A genetic basis for Pseudomonas aeruginosa biofilm antibiotic resistance.</a> Nature. 426 (6964), 306-310 (2003).</li><li>Mah, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilm-specific+antibiotic+resistance.">Biofilm-specific antibiotic resistance.</a> Future Microbiol. 7 (9), 1061-1072 (2012).</li><li>Beaudoin, T., Zhang, L., Hinz, A. J., Parr, C. J., Mah, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biofilm-specific+antibiotic+resistance+gene+ndvB+is+important+for+expression+of+ethanol+oxidation+genes+in+Pseudomonas+aeruginosa+biofilms.">The biofilm-specific antibiotic resistance gene ndvB is important for expression of ethanol oxidation genes in Pseudomonas aeruginosa biofilms.</a> J. Bacteriol. 194 (12), 3128-3136 (2012).</li><li>Beaudoin, T., Aaron, S. D., Giesbrecht-Lewis, T., Vandemheen, K., Mah, T. F. <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+clonal+strains+of+Pseudomonas+aeruginosa+isolated+from+cystic+fibrosis+patients+in+Ontario,+Canada.">Characterization of clonal strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients in Ontario, Canada.</a> Can. J. Microbiol. 56 (7), 548-557 (2010).</li><li>Vidya, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+infection+phenotypes+of+Pseudomonas+aeruginosa+are+associated+with+failure+of+eradication+in+children+with+cystic+fibrosis.">Chronic infection phenotypes of Pseudomonas aeruginosa are associated with failure of eradication in children with cystic fibrosis.</a> Eur.J.Clin.Microbiol.Infect.Dis. , (2015).</li><li>Beaudoin, T., Lafayette, S., Nguyen, D., Rousseau, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mucoid+Pseudomonas+aeruginosa+caused+by+mucA+mutations+result+in+activation+of+TLR2+in+addition+to+TLR5+in+airway+epithelial+cells.">Mucoid Pseudomonas aeruginosa caused by mucA mutations result in activation of TLR2 in addition to TLR5 in airway epithelial cells.</a> Biochem.Biophys.Res.Commun. 428 (1), 150-154 (2012).</li><li>Beaudoin, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+level+of+p38alpha+mitogen-activated+protein+kinase+activation+in+airway+epithelial+cells+determines+the+onset+of+innate+immune+responses+to+planktonic+and+biofilm+Pseudomonas+aeruginosa.">The level of p38alpha mitogen-activated protein kinase activation in airway epithelial cells determines the onset of innate immune responses to planktonic and biofilm Pseudomonas aeruginosa.</a> J.Infect.Dis. 207 (10), 1544-1555 (2013).</li><li>LaFayette, S. L., 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=Cystic+fibrosis-adapted+quorum+sensing+mutants+cause+hyperinflammatory+responses.">Cystic fibrosis-adapted quorum sensing mutants cause hyperinflammatory responses.</a> Sci.Adv. 1 (6), e1500199 (2015).</li><li>Staudinger, B. J., 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=Conditions+associated+with+the+cystic+fibrosis+defect+promote+chronic+Pseudomonas+aeruginosa+infection.">Conditions associated with the cystic fibrosis defect promote chronic Pseudomonas aeruginosa infection.</a> Am.J.Respir.Crit.Care Med. 189 (7), 812-824 (2014).</li><li>Kennedy, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activity+of+Tobramycin+against+Cystic+Fibrosis+Isolates+of+Burkholderia+cepacia+Complex+Grown+as+Biofilms.">Activity of Tobramycin against Cystic Fibrosis Isolates of Burkholderia cepacia Complex Grown as Biofilms.</a> Antimicrob.Agents Chemother. 60 (1), 348-355 (2015).</li><li>Tom, S. K., Yau, Y. C., Beaudoin, T., LiPuma, J. J., Waters, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+High-Dose+Antimicrobials+on+Biofilm+Growth+of+Achromobacter+Species+Isolated+from+Cystic+Fibrosis+Patients.">Effect of High-Dose Antimicrobials on Biofilm Growth of Achromobacter Species Isolated from Cystic Fibrosis Patients.</a> Antimicrob.Agents Chemother. 60 (1), 650-652 (2015).</li><li>Heydorn, 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=Quantification+of+biofilm+structures+by+the+novel+computer+program+COMSTAT.">Quantification of biofilm structures by the novel computer program COMSTAT.</a> Microbiology. 146 (Pt 10), 2395-2407 (2000).</li><li>Vorregaard, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Informatics and Mathematical Modelling. , (2008).</li><li>Jurcisek, J. A., Dickson, A. C., Bruggeman, M. E., Bakaletz, L. O. <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+Biofilm+Formation+in+an+8-well+Chamber+Slide.">In vitro Biofilm Formation in an 8-well Chamber Slide.</a> J. Vis. Exp. (47), e2481 (2011).</li></ol>

The methods described herein allow for visualization of bacterial biofilms grown in the presence of exogenous products. Not surprisingly, the production of the exoproducts is of importance when using this type of system. For instance, Dithiothreitol (DTT), is often used on human sputum samples to help liquefy the samples. However, the effect of DTT alone can decrease biofilm development and viability (data not shown). Thus, proper controls for all conditions are necessary. Furthermore, the addition of human sputum products creates inherent variability on the experiment due to the fact that the sputum of each patient has a unique microbiome. To adjust for this, we have used pooled sputum samples to avoid patient specific results. Additionally, the choice of appropriate media is important when using any model system. Standard media for biofilm growth of the intended organism are recommended for initial setup of the system. If the goal of the experiment is to identify how exogenous products are affecting biofilm formation, a nutrient rich media that provides adequate biofilm formation is suggested. This will allow sufficient nutrition for growth while determining how exogenous factors may affect the biofilm. Other media, such as minimal or defined media, can be used to better mimic certain conditions. Other media have been used with good results in this system (data not shown). The attachment of the biofilms to the chambered coverglass is robust, however great care must be taken when removing/adding media or during washing steps of the biofilms to prevent disrupting the biofilms.
The use of the live-dead stain as per manufacturer&#39;s protocol has yielded good results for the system described. A number of factors can affect the fluorescence ratio of the images (including dye uptake of bacteria, relative density of biofilm and detector gain settings), however, this method should relate to what is observed in the images. Other measures may be used to represent the relative amount of dead/live biofilm, such as the biomass from the dead cells as a ratio of the total biomass present in the biofilm (as derived from COMSTAT). Using bacterial counts to confirm biofilm viability in repeated experiments is recommended to confirm the visual observations of this model. Due to inherent heterogeneity of biofilms, multiple images from each chamber and multiple chambers should be used for each condition in an experiment. This adds to the cost and duration of these experiments.
The acquisition of images is important prior to the analysis of data from these experiments. Care must be taken to not over saturate images and when determining the microscope setup. Depending on the level of detail required and the microscope available, a number of different objectives (10X, 25X, 40X and 63X) can be used to acquire images, though we find that 25X objective gives better images. The thickness of the Z-stack can also affect overall image quality and level of detail. Having images taken every 0.5-1 &#956;m seems to provide clear images at 25X objective, while keeping the Z-stack images at a size that can be analyzed by COMSTAT on standard computer systems.
These experiments are more costly and time consuming than other attachment assays, and cannot be done in a high throughput manner. In this procedure, bacteria attach to a borosilicate surface, which is not reflective of an in vivo condition and may affect biofilm formation and development. However, they provide additional information and can generate hypotheses for mechanism related to biofilm antibiotic resistance and physiological response to exogenous signal. If the goal of the experiment is to understand how biofilms change in response to different factors, rather than identifying anti-biofilm compounds using high-throughput methods for instance, the additional information gained using this technique makes the method worthwhile. Thus the current method is a significant advancement over previous limited attachment assays such as the crystal violet assay, which is most commonly used to study biofilms.
Critical steps to this procedure include: 1) Ensuring timely processing of sputum samples to avoid degradation; 2) Being gentle with media changes on the biofilms to avoid disruption of the biofilm and 3) Doing repeated measurements of biofilm imaging to ensure an accurate representation of the biofilm thickness due to the heterogeneity of biofilm formation.
Once the system is set-up for a given bacterial species, one can test a number of different conditions, including the effects of exogenous factors on multiple clinical isolates. This system has been used to study the effect of antibiotics on biofilms exposed to human sputum16 and to compare highly resistant and intermediately resistant clinical isolates.17 Modifications to the chambered coverglass, such as coating the bottom with mucin or collagen micro-scaffold (e.g., puracol), can further extend the range of experiments possible. It may be possible to adapt this system to study direct interactions, such as those between epithelial cells and bacteria, or between different bacterial species. This is an expansion of the model described by Jurcisek et al.20 The method uses slide chamber growth similar to that described here and uses formalin to fix biofilms prior to visualization. Alternatively, in this method we visualize biofilms immediately after staining and do not use a fixative. In addition, we add exogenous factors to test the effect of antibiotic on biofilms. This model thus has the potential to considerably further our understanding of bacterial biofilms in human disease.

Bacterial biofilms are groups of microorganisms that are attached to one another and encased in a self-secreted matrix.1,2 Classically, they represent bacteria physically attached to an abiotic or biotic surface formed under conditions of flow. Biofilms have also been shown to grow in static conditions (absence of flow) and distal from surfaces, such as at the air-liquid interface of thermal pools or pellicles formed in test tubes. These biofilms have long been recognized in the environment and are a major detriment to industrial processes, as they can form in water reservoirs or in pipes, resulting in biofouling, corrosion and blockages.3,4
Biofilms are also critical in healthcare settings, as they have been shown be involved in catheter related infections, pulmonary infections in cystic fibrosis patients, as well as in numerous other infections.5,6 One of the hallmarks of biofilm infections is the decreased susceptibility of bacteria to antibiotics and impaired clearance by the innate immune system.7-9 The most well studied, clinically relevant scenarios involving biofilm-based infection occurs in patients with cystic fibrosis (CF), who are chronically infected with Pseudomonas aeruginosa biofilms. P. aeruginosa can undergo a number of changes during establishment of chronic infection that make it very difficult to treat.10,11 Biofilms can differentially activate innate immunity and drive inflammation.12-14 As these infections lead to increased morbidity and mortality in CF patients, it is crucial to understand factors that can affect biofilm development in this context.
A recent study suggests that host-factors are critical in the formation of P. aeruginosa biofilm aggregates.15 These biofilms contribute to reduced susceptibility to antibiotics and host defense mechanisms. The presence of host-derived factors, such as neutrophil elastase, as well as secreted products from microorganisms present in the CF lung, have the potential to greatly modulate biofilm formation and development.16 Additionally, biofilms interact with the host to modulate expression of numerous pathways and initiate inflammation. While high throughput methods, such as the standard crystal violet assay, can provide some information with regards to the biofilm process, visualization of the biofilm in response to these factors provide more in-depth information.
In this manuscript we describe a method for using factors from the sputum of patients with CF to study the development of biofilms in vitro. This method allows for rapid visualization of biofilms exposed to sputum containing host factors using a commercial biofilm viability kit. This technique can be used to visually identify changes that occur during biofilm growth in the presence of exogenous products, and represents an improved method to analyze the changes in biofilm development under various conditions.

<table><tbody><tr><td>Lab-Tek II Chambered coverglass, #1.5 borosilicate, 8-well</td><td>Thermo Sicher Scientific</td><td>155409</td><td></td></tr><tr><td>Filmtracer Live/Dead Biofilm Viabilty Kit</td><td>Thermo Fisher Scientific</td><td>L10316</td><td></td></tr><tr><td>Blood agar plates</td><td>Thermo Fisher Scientific</td><td>R10215</td><td>Confirming viability via CFU counts or selecting colonies for innoculation</td></tr><tr><td>COMSTAT</td><td>Availble software online</td><td></td><td>COMSTAT is software to analyze biofilm images. Available www.comstat.dk&amp;nbsp;</td></tr><tr><td>Millers LB Broth</td><td>Thermo Fisher Scientific</td><td>12780-052</td><td>Standard media for overnight gowth/biofilm growth</td></tr><tr><td>Millex-GV Syringe Filters</td><td>Millipore</td><td>SLGV013SL</td><td>Filtering of sputum supernants</td></tr><tr><td>Phosphate Buffered Saline (Dulbecco A)</td><td>Oxoid</td><td>BR0014G</td><td>Washing of biofilm chambers after media removal</td></tr><tr><td>Zeiss AxioVert 200M</td><td>Carl Zeiss</td><td></td><td></td></tr><tr><td>Hamamatsu C9100-13 EM-CCD</td><td>QS Technologies Inc.</td><td></td><td></td></tr><tr><td>Spectral Borealis</td><td>Qs Technologies Inc.</td><td></td><td></td></tr><tr><td>Perkin Elmer Volocity</td><td>QS Technologies Inc.</td><td></td><td>Instructions for this software can be found at: http://cellularimaging.perkinelmer.com/pdfs/manuals/VolocityuserGuide.pdf</td></tr></tbody></table>

visualizing the effects of sputum on biofilm development using a chambered coverglass model

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the development and persistence of many health related infections. One of the most well described and studied biofilms in human disease occurs in chronic pulmonary infection of cystic fibrosis patients. When studying biofilms in the context of the host, many factors can impact biofilm formation and development. In order to identify how host factors may affect biofilm formation and development, we used a static chambered coverglass method to grow biofilms in the presence of host-derived factors in the form of sputum supernatants. Bacteria are seeded into chambers and exposed to sputum filtrates. Following 48 hr of growth, biofilms are stained with a commercial biofilm viability kit prior to confocal microscopy and analysis. Following image acquisition, biofilm properties can be assessed using different software platforms. This method allows us to visualize key properties of biofilm growth in presence of different substances including antibiotics.

The overall design of the experiment is represented in Figure 1. The use of this protocol provides a convenient method to visualize the changes in biofilms grown for different periods of time (e.g., 24, 48 or 72 hr). Importantly, exogenous signals, such as sputum filtrates, can be added to visualize the changes in biofilm development. As seen in Figure 2, the presence of 10% sputum filtrates can change the architecture of the biofilm (Figure 2A, lower panels).16 These images can be analyzed using COMSTAT software to obtain key biofilm matrices, including average thickness of the biofilm, total biomass and surface coverage. This is reflected in an overall increase in biofilm thickness (Figures 2B, and 3).16 The effects of antibiotics on biofilms in the presence sputum is shown in Figure 3. By visualizing the changes in biofilm development, one can better appreciate how different factors can affect biofilm growth, to a much better extent than traditional biofilm assays, such as crystal violet staining.
<img alt="Figure 1" src="/files/ftp_upload/54819/54819fig1.jpg" /> 
Figure 1: Overall design of experiment. Flow diagram of basic protocol. An overnight (O/N) culture is diluted 1/1,000 and allowed to grow to a final OD600 of 0.5. This is further diluted 1/1,000 and 200 &#181;l is seeded into well of chambered coverglass and allowed to attach for 3-4 hr. Following this, media is removed and replaced with fresh media. Biofilms are allowed to grow for desired time. Media, exogenous products or antibiotics can be added to the biofilms. Following growth, media is removed, biofilms are stained and confocal imaging is performed. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54819/54819fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/54819/54819fig2.jpg" /> 
Figure 2: Representative images of biofilm development following exposure to sputum filtrates. (A) Representative images of Burkholderia cepacia complex (BCC) clinical isolates following 48 hr of growth in chambered coverglass with media alone (top panels) or in the presence of 10% sputum filtrates (lower panels) followed by staining with biofilm viability kit. 1 scale unit represent 19.68 &#956;m. (B-C) Average thickness of isolates (B) and dead:live ratio (C) of multiple images of BCC isolates grown for 48 hr in slide chambers in the absence (white bars) or presence (black bars) of sputum filtrates . Each bar represents the mean of 45 images plotted with the standard error of the mean. **p &#60;0.001 compared to control (media alone) using Kruskal-Wallis test. Figure adapted from Kennedy et al.16 <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54819/54819fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/54819/54819fig3.jpg" /> 
Figure 3: Representative images of antibiotic treatment on biofilms exposed to sputum filtrate. (A) Images of Burkholderia vietnamiensis clinical isolates following 48 hr of growth in chambered coverglass with media alone (left) or in the presence of 10% sputum filtrates (right) with or without 1,000 &#956;g/m of tobramycin. Biofilms were grown for 24 hr in media alone or media supplemented with 10% (v/v) sputum filtrates. After 24 hr, media was removed and replaced with media (+/- sputum) containing antibiotics. 1 scale unit represent 19.68 &#956;m. (B-C) Average thickness of isolates (B) and dead:live ratio (C) of multiple images (n = 9) of B. vietnamiensis isolates grown for 48 hr in slide chambers in the absence or presence of sputum filtrates . Each bar represents the mean of 45 images plotted with the standard error of the mean. **p &#60;0.001 compared to control (0 &#181;g/ml) using Kruskal-Wallis test. Figure adapted from Kennedy et al.16 <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54819/54819fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

This protocol describes the visualization of biofilm development following exposure to host-factors using a slide chamber model. This model allows for direct visualization of biofilm development as well as analysis of biofilm parameters using computer software programs.

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the ...

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8.3K Views.  Hospital for Sick Children. This protocol describes the visualization of biofilm development following exposure to host-factors using a slide chamber model. This model allows for direct visualization of biofilm development as well as analysis of biofilm parameters using computer software programs.

Video: Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living surfaces. In this paper, we describe protocols for forming Pseudomonas aeruginosa biofilms on human airway epithelial cells (CFBE cells) grown in culture. In the first method (termed the Static Co-culture Biofilm Model), P. aeruginosa is incubated with CFBE cells grown as confluent monolayers on standard tissue culture plates. Although the bacterium is quite toxic to epithelial cells, the addition of arginine delays the destruction of the monolayer long enough for biofilms to form on the CFBE cells. The second method (termed the Flow Cell Co-culture Biofilm Model), involves adaptation of a biofilm flow cell apparatus, which is often used in biofilm research, to accommodate a glass coverslip supporting a confluent monolayer of CFBE cells. This monolayer is inoculated with P. aeruginosa and a peristaltic pump then flows fresh medium across the cells. In both systems, bacterial biofilms form within 6-8 hours after inoculation. Visualization of the biofilm is enhanced by the use of P. aeruginosa strains constitutively expressing green fluorescent protein (GFP). The Static and Flow Cell Co-culture Biofilm assays are model systems for early P. aeruginosa infection of the Cystic Fibrosis (CF) lung, and these techniques allow different aspects of P. aeruginosa biofilm formation and virulence to be studied, including biofilm cytotoxicity, measurement of biofilm CFU, and staining and visualizing the biofilm.

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

This paper describes different methods of growing Pseudomonas aeruginosa biofilms on cultured human airway epithelial cells. These protocols can be adapted to study different aspects of biofilm formation, including visualization of the biofilm, staining of the biofilm, measuring the colony forming units (CFU) of the biofilm, and studying biofilm cytotoxicity.

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living ...

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological properties compared to free living microorganisms. Biofilms in nature are often difficult to investigate and reside under poorly defined conditions1. Using a transparent substratum it is possible to device a system where simple biofilms can be examined in a non-destructive way in real-time: here we demonstrate the assembly and operation of a flow cell model system, for in vitro 3D studies of microbial biofilms generating high reproducibility under well-defined conditions2,3.
The system consists of a flow cell that serves as growth chamber for the biofilm. The flow cell is supplied with nutrients and oxygen from a medium flask via a peristaltic pump and spent medium is collected in a waste container. This construction of the flow system allows a continuous supply of nutrients and administration of e.g. antibiotics with minimal disturbance of the cells grown in the flow chamber. Moreover, the flow conditions within the flow cell allow studies of biofilm exposed to shear stress. A bubble trapping device confines air bubbles from the tubing which otherwise could disrupt the biofilm structure in the flow cell.
The flow cell system is compatible with Confocal Laser Scanning Microscopy (CLSM) and can thereby provide highly detailed 3D information about developing microbial biofilms. Cells in the biofilm can be labeled with fluorescent probes or proteins compatible with CLSM analysis. This enables online visualization and allows investigation of niches in the developing biofilm. Microbial interrelationship, investigation of antimicrobial agents or the expression of specific genes, are of the many experimental setups that can be investigated in the flow cell system.

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Protocol describing the application of a flow cell system for growing and analyzing microbial biofilms for Confocal Laser Scanning Microscopy (CLSM).

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological ...

Microtiter Dish Biofilm Formation Assay

Biofilms are communities of microbes attached to surfaces, which can be found in medical, industrial and natural settings. In fact, life in a biofilm probably represents the predominate mode of growth for microbes in most environments. Mature biofilms have a few distinct characteristics. Biofilm microbes are typically surrounded by an extracellular matrix that provides structure and protection to the community. Microbes growing in a biofilm also have a characteristic architecture generally comprised of macrocolonies (containing thousands of cells) surrounded by fluid-filled channels. Biofilm-grown microbes are also notorious for their resistance to a range of antimicrobial agents including clinically relevant antibiotics.
The microtiter dish assay is an important tool for the study of the early stages in biofilm formation, and has been applied primarily for the study of bacterial biofilms, although this assay has also been used to study fungal biofilm formation. Because this assay uses static, batch-growth conditions, it does not allow for the formation of the mature biofilms typically associated with flow cell systems. However, the assay has been effective at identifying many factors required for initiation of biofilm formation (i.e, flagella, pili, adhesins, enzymes involved in cyclic-di-GMP binding and metabolism) and well as genes involved in extracellular polysaccharide production. Furthermore, published work indicates that biofilms grown in microtiter dishes do develop some properties of mature biofilms, such a antibiotic tolerance and resistance to immune system effectors.
This simple microtiter dish assay allows for the formation of a biofilm on the wall and/or bottom of a microtiter dish. The high throughput nature of the assay makes it useful for genetic screens, as well as testing biofilm formation by multiple strains under various growth conditions. Variants of this assay have been used to assess early biofilm formation for a wide variety of microbes, including but not limited to, pseudomonads, Vibrio cholerae, Escherichia coli, staphylocci, enterococci, mycobacteria and fungi.
In the protocol described here, we will focus on the use of this assay to study biofilm formation by the model organism Pseudomonas aeruginosa. In this assay, the extent of biofilm formation is measured using the dye crystal violet (CV). However, a number of other colorimetric and metabolic stains have been reported for the quantification of biofilm formation using the microtiter plate assay. The ease, low cost and flexibility of the microtiter plate assay has made it a critical tool for the study of biofilms.

The assay describes a rapid means to measure early biofilm formation in bacteria and fungi. This method uses a microtiter plate as the substratum for microbial biofilm formation, and the biofilm is visualized using crystal violet strain. The assay provides either a qualitative or quantitative assay for early biofilm formation.

Biofilms are communities of microbes attached to surfaces, which can be found in medical, industrial and natural settings.  In fact, life in a biofilm ...

In vitro Biofilm Formation in an 8-well Chamber Slide

The chronic nature of many diseases is attributed to the formation of bacterial biofilms which are recalcitrant to traditional antibiotic therapy. Biofilms are community-associated bacteria attached to a surface and encased in a matrix. The role of the extracellular matrix is multifaceted, including facilitating nutrient acquisition, and offers significant protection against environmental stresses (e.g. host immune responses). In an effort to acquire a better understanding as to how the bacteria within a biofilm respond to environmental stresses we have used a protocol wherein we visualize bacterial biofilms which have formed in an 8-well chamber slide. The biofilms were stained with the BacLight Live/Dead stain and examined using a confocal microscope to characterize the relative biofilm size, and structure under varying incubation conditions. Z-stack images were collected via confocal microscopy and analyzed by COMSTAT. This protocol can be used to help elucidate the mechanism and kinetics by which biofilms form, as well as identify components that are important to biofilm structure and stability.

In vitro Biofilm Formation in an 8-well Chamber Slide

This article describes the procedure for the formation and visualization of a bacterial biofilm grown within an 8-well chamber slide

The chronic nature of many diseases is attributed to the formation of bacterial biofilms which are recalcitrant to traditional antibiotic therapy. ...

Use of a High-throughput In Vitro Microfluidic System to Develop Oral Multi-species Biofilms

There are few high-throughput in vitro systems which facilitate the development of multi-species biofilms that contain numerous species commonly detected within in vivo oral biofilms. Furthermore, a system that uses natural human saliva as the nutrient source, instead of artificial media, is particularly desirable in order to support the expression of cellular and biofilm-specific properties that mimic the in vivo communities. We describe a method for the development of multi-species oral biofilms that are comparable, with respect to species composition, to supragingival dental plaque, under conditions similar to the human oral cavity. Specifically, this methods article will describe how a commercially available microfluidic system can be adapted to facilitate the development of multi-species oral biofilms derived from and grown within pooled saliva. Furthermore, a description of how the system can be used in conjunction with a confocal laser scanning microscope to generate 3-D biofilm reconstructions for architectural and viability analyses will be presented. Given the broad diversity of microorganisms that grow within biofilms in the microfluidic system (including Streptococcus, Neisseria, Veillonella, Gemella, and Porphyromonas), a protocol will also be presented describing how to harvest the biofilm cells for further subculture&#160;or DNA extraction and analysis. The limits of both the microfluidic biofilm system and the current state-of-the-art data analyses will be addressed. Ultimately, it is envisioned that this article will provide a baseline technique that will improve the study of oral biofilms and aid in the development of additional technologies that can be integrated with the microfluidic platform.

Use of a High-throughput In Vitro Microfluidic System to Develop Oral Multi-species Biofilms

The goal of this methods paper is to describe the use of a microfluidic system for the development of multi-species biofilms that contain species typically identified in human supragingival dental plaque.&#160;Methods to describe biofilm architecture, biofilm viability, and an approach to harvest biofilm for culture-dependent or culture-independent analyses are highlighted.

There are few high-throughput in vitro systems which facilitate the development of multi-species biofilms that contain numerous species commonly detected ...

Bioengineering

Methodologies for Studying B. subtilis Biofilms as a Model for Characterizing Small Molecule Biofilm Inhibitors

This work assesses different methodologies to study the impact of small molecule biofilm inhibitors, such as D-amino acids, on the development and resilience of Bacillus subtilis biofilms. First, methods are presented that select for small molecule inhibitors with biofilm-specific targets in order to separate the effect of the small molecule inhibitors on planktonic growth from their effect on biofilm formation. Next, we focus on how inoculation conditions affect the sensitivity of multicellular, floating B. subtilis cultures to small molecule inhibitors. The results suggest that discrepancies in the reported effects of such inhibitors such as D-amino acids are due to inconsistent pre-culture conditions. Furthermore, a recently developed protocol is described for evaluating the contribution of small molecule treatments towards biofilm resistance to antibacterial substances. Lastly, scanning electron microscopy (SEM) techniques are presented to analyze the three-dimensional spatial arrangement of cells and their surrounding extracellular matrix in a B. subtilis biofilm. SEM facilitates insight into the three-dimensional biofilm architecture and the matrix texture. A combination of the methods described here can greatly assist the study of biofilm development in the presence and absence of biofilm inhibitors, and shed light on the mechanism of action of these inhibitors.

Methodologies for Studying B. subtilis Biofilms as a Model for Characterizing Small Molecule Biofilm Inhibitors

This study presents the development of reproducible methodologies to study biofilm inhibitors and their effects on Bacillus subtilis multicellularity.

This work assesses different methodologies to study the impact of small molecule biofilm inhibitors, such as D-amino acids, on the development and ...

The WinCF Model - An Inexpensive and Tractable Microcosm of a Mucus Plugged Bronchiole to Study the Microbiology of Lung Infections

Many chronic airway diseases result in mucus plugging of the airways. Lungs of an individual with cystic fibrosis are an exemplary case where their mucus-plugged bronchioles create a favorable habitat for microbial colonization. Various pathogens thrive in this environment interacting with each other and driving many of the symptoms associated with CF disease. Like any microbial community, the chemical conditions of their habitat have a significant impact on the community structure and dynamics. For example, different microorganisms thrive in differing levels of oxygen or other solute concentrations. This is also true in the CF lung, where oxygen concentrations are believed to drive community physiology and structure. The methods described here are designed to mimic the lung environment and grow pathogens in a manner more similar to that from which they cause disease. Manipulation of the chemical surroundings of these microbes is then used to study how the chemistry of lung infections governs its microbial ecology. The method, called the WinCF system, is based on artificial sputum medium and narrow capillary tubes meant to provide an oxygen gradient similar to that which exists in mucus-plugged bronchioles. Manipulating chemical conditions, such as the media pH of the sputum or antibiotics pressure, allows for visualization of the microbiological differences in those samples using colored indicators, watching for gas or biofilm production, or extracting and sequencing the nucleic acid contents of each sample.

The mucus plugged airways of cystic fibrosis (CF) patients are an ideal environment for microbial pathogens to thrive. The manuscript describes a novel method for studying the CF lung microbiome in an environment that mimics where they cause disease and how alterations of chemical conditions can drive microbial dynamics.

Many chronic airway diseases result in mucus plugging of the airways. Lungs of an individual with cystic fibrosis are an exemplary case where their ...

Visualization of Biofilm Formation in Candida albicans Using an Automated Microfluidic Device

Candida albicans is the most common fungal pathogen of humans, causing about 15% of hospital-acquired sepsis cases. A major virulence attribute of C. albicans is its ability to form biofilms, structured communities of cells attached to biotic and abiotic surfaces. C. albicans biofilms can form on host tissues, such as mucosal layers, and on medical devices, such as catheters, pacemakers, dentures, and joint prostheses. Biofilms pose significant clinical challenges because they are highly resistant to physical and chemical perturbations, and can act as reservoirs to seed disseminated infections. Various in vitro assays have been utilized to study C. albicans biofilm formation, such as microtiter plate assays, dry weight measurements, cell viability assays, and confocal scanning laser microscopy. All of these assays are single end-point assays, where biofilm formation is assessed at a specific time point. Here, we describe a protocol to study biofilm formation in real-time using an automated microfluidic device under laminar flow conditions. This method allows for the observation of biofilm formation as the biofilm develops over time, using customizable conditions that mimic those of the host, such as those encountered in vascular catheters. This protocol can be used to assess the biofilm defects of genetic mutants as well as the inhibitory effects of antimicrobial agents on biofilm development in real-time.

Visualization of Biofilm Formation in Candida albicans Using an Automated Microfluidic Device

This protocol describes the use of a customizable automated microfluidic device to visualize biofilm formation in Candida albicans under host physiological conditions.

Candida albicans is the most common fungal pathogen of humans, causing about 15% of hospital-acquired sepsis cases. A major virulence attribute of C. ...

Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients

Early detection and eradication of Pseudomonas aeruginosa within the lungs of cystic fibrosis patients can reduce the chance of developing chronic infection. The development of chronic P. aeruginosa infections is associated with a decline in lung function and increased morbidity. Therefore, there is a great interest in elucidating the reasons for the failure to eradicate P. aeruginosa with antibiotic therapy which occurs in approximately 10-40% of pediatric patients. One of many factors that can affect host clearance of P. aeruginosa and antibiotic susceptibility is variations in spatial organization (such as aggregation or biofilm formation) and polysaccharide production. Therefore, we were interested in visualizing the in situ characteristics of P. aeruginosa within the sputum of CF patients. A tissue clearing technique was applied to sputum samples after embedding the samples into a hydrogel matrix to retain the 3D structures relative to host cells. After tissue clearing, fluorescent labels and dyes were added to allow visualization. Fluorescence in situ hybridization was performed for the visualization of bacterial cells, binding of fluorescently labeled anti-Psl-antibodies for the visualization of the exopolysaccharide and DAPI staining to stain host cells to obtain structural insight. These methods allowed for the high-resolution imaging of P. aeruginosa within the sputum of CF patients via confocal laser scanning microscopy.

Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients

This protocol provides methods for visualization of bacterial cells and polysaccharide synthesis locus (Psl) polysaccharide within the sputum of cystic fibrosis patients.

Early detection and eradication of Pseudomonas aeruginosa within the lungs of cystic fibrosis patients can reduce the chance of developing chronic ...

Quantifying the Effects of Antimicrobials on In vitro Biofilm Architecture using COMSTAT Software

Biofilms are aggregates of microorganisms that rely on a self-produced matrix of extracellular polymeric substance for protection and structural integrity. The nosocomial pathogen, Pseudomonas aeruginosa, is known to adopt a biofilm mode of growth, causing chronic pulmonary infection in patients with cystic fibrosis (CF). The computer program, COMSTAT, is a useful tool for quantifying antimicrobial-induced changes in P. aeruginosa biofilm architecture by extracting data from three-dimensional confocal images. However, standardized operation of the software is less commonly addressed, which is important for optimal reporting of biofilm behavior and cross-center comparison. Thus, the aim of this protocol is to provide a simple and reproducible framework for quantifying in vitro biofilm structures under varying antimicrobial conditions via COMSTAT. The technique is modeled using a CF P. aeruginosa isolate, grown in the form of biofilm replicates, and exposed to tobramycin and the anti-Psl monoclonal antibody, Psl0096. The step-by-step approach aims to reduce user ambiguity and minimize the chance of overlooking crucial image-processing steps. Specifically, the protocol emphasizes the elimination of subjective variations associated with the manual operation of COMSTAT, including image segmentation and the selection of appropriate quantitative analysis functions. Although this method requires users to spend additional time processing confocal images prior to running COMSTAT, it helps minimize misrepresented biofilm heterogenicity in automated outputs.

Quantifying the Effects of Antimicrobials on In vitro Biofilm Architecture using COMSTAT Software

Antimicrobial-induced changes to Pseudomonas aeruginosa biofilm architecture differ among clinical isolates cultured from patients with cystic fibrosis and chronic pulmonary infection. Following confocal microscopy, COMSTAT software can be utilized to quantify variations in biofilm architecture (e.g., surface area, thickness, biomass) for individual isolates to assess the efficacy of anti-infective agents.

Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

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Chapters in this video

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Microtiter Dish Biofilm Formation Assay

In vitro Biofilm Formation in an 8-well Chamber Slide

Use of a High-throughput In Vitro Microfluidic System to Develop Oral Multi-species Biofilms

Methodologies for Studying B. subtilis Biofilms as a Model for Characterizing Small Molecule Biofilm Inhibitors

The WinCF Model - An Inexpensive and Tractable Microcosm of a Mucus Plugged Bronchiole to Study the Microbiology of Lung Infections

Visualization of Biofilm Formation in Candida albicans Using an Automated Microfluidic Device

Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients

Quantifying the Effects of Antimicrobials on In vitro Biofilm Architecture using COMSTAT Software