Figure 6.

An example of a Minimal Biofilm Inhibitory Concentration (MBIC) assay for eight anti-biofilm compounds that were tested against S. epidermidis 18972. The assay plate in which biofilm cultures have been stained with crystal violet is shown in the photograph. The concentrations of each compound tested are indicated above the plate, and the compound tested in each row is indicated on the left side of the plate. The MBIC and MIC are defined as the lowest compound concentration that produces a ≥ 80% inhibition of biofilm growth or planktonic growth, respectively. The compounds used in this assay (Compounds 1–8), their chemical names and structures, and the MBIC and MIC values obtained as a result of the assay are also shown. Note that Gentian violet produced an MIC that was equal to the MBIC. Because this compound strongly absorbs light at 600 nm, the antibacterial activity of this compound became apparent only when it was diluted in the dose response assay. The compounds used in this assay are commercially available from MicroSource Discovery Systems, Gaylordsville, CT). Alternatively, three of these compounds (Tomatidine, Actinonin, and Emodin) can be purchased from Sigma-Aldrich (St. Louis, MO). MBX-1240 can be purchased from ChemBridge Corp. (San Diego, CA).