Cell surface proteins of indigenous probiotics render antagonistic and protective effect on gut barrier integrity against extended-spectrum beta-lactamase (ESBL) <i>Escherichia coli</i>

Gut-mediated infections fostered by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are increasingly prevalent in clinical settings, posing a significant challenge to the efficacy of conventional antibiotic therapy. This underscores the urgent need to identify alternatives-to-antibiotics. In this study, we investigated the antagonistic potential of total surface proteins derived from probiotic strains viz. Limosilactobacillus fermentum LbS4 (MTCC 5954), L. fermentum Lf1 (MTCC 5689), Lactobacillus acidophilus NCFM, and Lacticaseibacillus rhamnosus GG (LGG), against clinical isolates of ESBL E. coli (9/234 and 23/208). Surface proteins were extracted using lithium chloride as chaotropic agent. Surface proteins exhibited strain-specific heterogeneity, as revealed by SDS-PAGE profiling. These proteins significantly (P < 0.05) reduced E. coli muco-adhesion through protective (hampering the bacterial adhesion), competitive (competition for adhesion sites), and displacement (dislodgement of adhered bacteria) mechanisms. While remaining non-toxic, surface proteins revealed anti-colonization efficacy against ESBL E. coli on HT-29 cell line and preserved epithelial integrity, as demonstrated by FITC-dextran transflux assays. In contrast, ESBL E. coli (109 CFU mL-1) compromised epithelial integrity by increasing FITC-dextran permeability, which was significantly (P < 0.05) mitigated by co-treatment with surface proteins. Overall, this study highlights the potential of probiotic-derived surface proteins as promising postbiotic candidates for countering ESBL E. coli colonization and preserving gut barrier integrity.