Cefoxitin inhibits the formation of biofilm involved in antimicrobial resistance MDR <i>Escherichia coli</i>

The study investigates the relationship between biofilm formation and antibiotic resistance in <i>Escherichia coli</i> (<i>E. coli</i>) isolated from calves. Using biochemical and molecular methods, we identified the isolates and assessed their biofilm-forming ability through an improved crystal violet staining method. The minimum inhibitory concentrations (MICs) of 18 antibiotics against the isolates were determined using the broth microdilution method. The impact of cefoxitin on biofilm formation was analyzed using laser scanning confocal microscopy (LSCM). Additionally, qRT-PCR was employed to evaluate the expression levels of biofilm-related genes (<i>luxS, motA, fliA, pfs, and csgD</i>) in response to varying cefoxitin concentrations. Results indicated a significant correlation between antimicrobial resistance (AMR) and biofilm formation ability. Cefoxitin effectively reduced biofilm formation of multidrug-resistant <i>E. coli</i> isolates at 1/2 and 1 MIC, with enhanced inhibition at higher concentrations. The QS-related genes <i>luxS, pfs, motA,</i> and <i>fliA</i> were downregulated, leading to decreased <i>csgD</i> expression. At 1/2 MIC, <i>csgD</i> expression was significantly reduced. In conclusion, cefoxitin inhibits biofilm formation in multidrug-resistant <i>E. coli</i> by down-regulating key genes, offering a potential strategy to mitigate resistance and control infections in calves caused by biofilm-positive <i>E. coli</i> isolates.