RESUMO
Objective: The purpose of the present study was to characterize the effects of medium, optical density (OD), andincubation time on biofilm formation by Escherichia coli in brain heart infusion (BHI) and Luria-Bertani broth(LB). Methods: The main procedure involved fixing the bacterial film with 95% ethanol, staining with 0.1% crystalviolet, releasing the bound dye with 33% glacial acetic acid, and measuring the OD of the solution at 570 nm using amicroplate reader. Results: It was found that 3 and 5 days of incubation are critical for biofilm formation as indicatedby the OD values of 0.55–0.35 and 0.70–0.39 in BHI and LB, respectively, at OD 0.05. Similarly, pattern in resultswas noted for OD 0.1 in both media BHI and LB. Conclusion: It is confirmed that 3 days (72 h) are required forobtaining effective biofilm formation in both BHI and LB at 37°C at OD 0.05 and 0.1.