TLR4 and escherichia coli infection: Both oral administration of 4-PBA and fecal microbiota transplantation (FMT) had strong resistance to E. coli infection, improved survival rate and body weight, reduced intestinal tissue damage, decreased the levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β), and restrained TLR4/MyD88/NF-κB pathway.