Biofilm formation of a strain of bovine Escherichia coli and analysis of its influencing factors

This study investigated the biofilm (BF) formation of a bovine-derived Escherichia coli (E. coli) strain (designated DL1907) and analyzed the factors influencing its formation. The BF-forming capacity, optimal formation time and temperature, as well as the effects of different culture media, pH levels, NaCl concentrations, and glucose concentrations, were assessed using the crystal violet method. The results demonstrated that the strain had a strong BF-forming capacity, achieving the most intact BF structure after 36 h of culture at 37°C. Trypticase Soy Broth (TSB) medium promoted the strongest BF formation compared to Luria-Bertani (LB) and Müller-Hinton Broth (MH) media. The optimal BF growth was achieved at a NaCl concentration of 0.5%, while higher concentrations (> 0.5%) significantly inhibited BF formation. The strain demonstrated a strong capability for BF formation at pH 7, while acidic or alkaline conditions significantly impaired its BF-forming capacity. The minimum BF inhibitory concentrations (MBIC) of baicalin, berberine, andrographolide, and emodin against BF were 512 μg/mL, 64 μg/mL, 64 μg/mL, and 128 μg/mL, respectively. For the antibiotics, the MBIC values of ceftazidime, kanamycin, enrofloxacin, and florfenicol were 256 μg/mL, 128 μg/mL, 64 μg/mL, and 32 μg/mL, respectively. The above experimental results are intended to provide data support for the clearance of the isolated strain DL1907 BF.