Antibiofilm Inhibitor Ferulic Acid as an Antibacterial Synergist Against Escherichia coli

<i>Escherichia coli</i> (<i>E. coli</i>) is a severe foodborne pathogen, and the formation of its biofilm can enhance bacterial virulence and reduce antibiotic sensitivity, posing a significant threat to human and animal health. Ferulic Acid (FA) is a natural active product that has been proven to possess various biological activities, including anti-inflammatory, antioxidant, and antitumor properties. This study evaluated the inhibitory effect of FA on the biofilm formation of <i>E. coli</i> through crystal violet (CV) staining and scanning electron microscopy (SEM) and investigated the synergistic effect of FA with antibiotics, using the alamar blue (AB) assay. In addition, the regulatory effect of FA on the transcription of biofilm-related genes was analyzed using qRT-PCR technology. The results showed that FA could significantly inhibit biofilm formation, reduce the production of extracellular polymeric substances (EPS), and weaken bacterial motility, without affecting bacterial growth and metabolic activity. qRT-PCR analysis revealed that FA significantly downregulated the expression of curli-related gene <i>csgD</i>, flagella-related genes (<i>flhC</i>, <i>flhD</i>, and <i>motA</i>), and type I fimbriae gene <i>fimA</i>, while upregulating the transcription of c-di-GMP-related genes (<i>pdeR</i>, <i>pdeA</i>, and <i>dosP</i>). It is noteworthy that FA exhibits significant synergistic antibacterial effects when combined with clinically commonly used antibiotics, including sodium fosfomycin, ceftriaxone, gentamicin, and tetracycline, with the most prominent synergistic effect observed in the combination of FA and sodium fosfomycin. These results confirm that FA possesses notable anti-biofilm activity and novel synergistic antibacterial properties, providing a potential therapeutic strategy for treating <i>E. coli</i> infections.