Optimization of processing conditions for the quantification of enterococci biofilms using microtitre-plates.

We performed a comparison of four selected protocols from the literature using microtitre-plate and colorimetric biomass assay for evaluation of enterococci biofilm formation ability and optimized a protocol after the identification and stringent performance of biofilm formation steps. The optimized protocol uses a dynamic model that provided a greater discrimination of enterococci biofilm formation ability, and could better simulate in vivo real conditions. Moreover different biofilm quantification approaches, such as the colorimetric biomass (crystal violet), the resazurin and CFU's assays could be used with the optimized protocol, with adequate reproducibility. This study also recognizes that parameters such as the biofilm formation index (BFi), the cut-off values and the Z' factor provide greater accuracy, possibility of inter and intra laboratory comparison and quality evaluation of the biofilm screening assays, respectively.