Infant-derived Bifidobacterium strains screened in vitro for alleviating intestinal disorder caused by Escherichia coli.

INTRODUCTION

Escherichia coli (E. coli) is a common foodborne pathogen that can cause various infections such as diarrhea and meningitis.

METHODS

In this study, 38 Bifidobacterium strains isolated from healthy breastfed infants were evaluated in vitro. D2, which demonstrated the strongest antagonism against E. coli and the most favorable probiotic properties, was selected for further investigation in vivo. The acid removal experiment of the cell-free supernatant (CFS) of D2 was conducted. Animal experiments were also performed, comparing D2 with A14 (a strain showing no antibacterial effect in vitro).

RESULTS

Acetic acid was identified as the main antibacterial substance in the CFS of D2 (P < 0.05). The CFS of D2 inhibited E. coli through multiple mechanisms, including inhibiting biofilm formation, damaging the integrity of the E. coli cell wall/membrane, and causing content leakage, ultimately leading to bacterial death. Furthermore, D2 significantly reduced the adhesion and invasion of E. coli on HT29 cells (P < 0.05). Compared with A14, D2 significantly reversed colonic damage caused by E. coli, restored cytokine expression, and promoted the expression of tight junction proteins. Additionally, D2 effectively ameliorated E. coli-induced gut microbiota dysbiosis and restored microbial diversity. It significantly reduced the abundance of Escherichia and promoted the abundance of beneficial bacterial genera such as Lachnospiraceae_NK4A136_group in the intestines.

DISCUSSION: These results indicate that D2 inhibits E. coli through multiple target points and represents a potential candidate strain for alleviating intestinal disorders caused by E. coli, or an alternative to antibiotics.