Objective: The purpose of the present study was to characterize the effects of medium, optical density and incubation time on biofilm formation by E. coli in Brain Heart Infusion (BHI) and Luria Broth (LB).
Methods: The main procedure involved fixing the bacterial film with 95% ethanol, staining with 0.1% crystal violet, releasing the bound dye with 33% glacial acetic acid, and measuring the optical density (OD) of the solution at 570 nm by using a microplate reader.
Results: It was found that 3 and 5 days of incubation are critical for biofilm formation as indicated by 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 results was noted for OD 0.1 in both media BHI and LB.
Conclusion: It is confirmed that three days (72 hours) are required for obtaining effective biofilm formation in both BHI and LB at 37℃ at OD 0.05 and 0.1.
Key words: Biofilm, E. coli, Brain heart broth, Luria broth, Optical density
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