Comparison of the reflectance and Crystal Violet assays for measurement of biofilm formation by Enterococcus
Broschat, Shira L.
Call, Douglas R.
Loge, Frank J.
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In previous work, we described a protocol for measuring biofilm formation on opaque and non-opaque surfaces using reflected light. In the present work, we used the reflectance assay to assess biofilm formation for 14 strains of Enterococcus and compared our results with those obtained using a Crystal Violet (CV) assay. In general, the results for the two assays were in agreement: both identified the same Enterococcus strain as the highest biofilm-forming strain and the same two strains as the lowest biofilm-forming strains. However, two Enterococcus strains identified as high biofilm formers by the CV assay were not identified as such by the reflectance assay. A single numerical value was obtained for each of the reflectance assay results that corresponded well with the confluence of a biofilm (and presumably its depth) using phase contrast microscopy.