Relationship between the biofilm optical density and heat tolerance (D60°C) of E. coli by source of isolates: live cattle (A), hide of carcass (B), hide-off carcass (C), beef products (D), and processing equipment (E). Isolates having relatively heightened heat resistance and biofilm-forming capacity are circled. Rsq, coefficient of determination; AdjRsq, adjusted coefficient of determination; RMSE, mean squared error of the coefficient of determination.