4-Hydroxycoumarin inhibits biofilm formation and enhances antibiotic efficacy against Escherichia coli O157:H7

Abstract

Conventional bactericidal antibiotics often fail to eradicate Escherichia coli O157:H7 ( E. coli O157) infections due to biofilm-mediated antimicrobial tolerance, and monotherapy can inadvertently drive resistance selection. This study aimed to identify compounds capable of modulating LuxS/AI-2-related phenotypes and to evaluate their potential to disrupt biofilms and enhance antibiotic efficacy against E. coli O157. The effects of 4-HC on biofilm formation, extracellular polymeric substance (EPS) biosynthesis, and flagella-mediated motility were assessed in vitro. Antibiotic potentiation was evaluated through combination assays across multiple antibiotic classes. In vivo efficacy was tested in a murine systemic infection model, with qualitative histological observation used to evaluate splenic, hepatic, and ileal tissue damage. 4-HC disrupted biofilm formation by suppressing EPS biosynthesis and flagella-mediated motility, thereby destabilizing biofilm architecture and impairing bacterial dissemination. 4-HC acted as a broad-range potentiator for most antibiotics tested, with the most pronounced effect observed in combination with fosfomycin sodium. This combination reduced systemic bacterial burden and restored intestinal barrier function in vivo . In the murine model, the 4-HC–fosfomycin regimen improved survival and markedly attenuated splenic necrosis and ileal tissue damage, with efficacy superior to monotherapy. 4-HC disrupts biofilm formation and enhances antibiotic efficacy against E. coli O157 infection, supporting the strategy of combining biofilm-modulating adjuvants with conventional antibiotics to combat antimicrobial resistance. However, rigorous safety evaluation is required before clinical translation.