Oral-Delivery Lactococcus lactis expressing cherry fusion lactoferrin peptides against infection of avian pathogenic Escherichia coli in chickens

Avian pathogenic Escherichia coli (APEC) infections result in significant economic losses and reduced animal welfare. Historically, antibiotics and vaccinations currently control APEC infections in poultry, however, antibiotic-resistant strains and heterologous serotypes limit their effectiveness. Meanwhile, antibiotic-resistant strains can be transmitted to humans via contact with animals, food or their environment. Probiotics and antimicrobial peptides (AMPs) are potential alternatives to antibiotics and represent promising strategies to combat APEC. Bovine lactoferricin and lactoferrampin possess anti-bacterial, anti-inflammatory, and anti-oxidant properties. Lactococcus lactis (L. lactis) is an excellent vector for delivering recombinant proteins. In this research, we generated a recombinant L. lactis strain MG1363 expressing lactoferrin peptides, which was labeled with a fluorescent marker mCherry and lacked an antibiotic resistance gene (LL-EFLmC). Our investigation focused on the impact of LL-EFLmC strain on the gut microbiota composition and avian pathogenic E. coli O78 challenge. Our findings indicate that LL-EFLmC exhibits inhibitory effects against APEC-O78 and Staphylococcus aureus CVCC26003 (S. aureus CVCC26003) in vitro. Furthermore, the inclusion of LL-EFLmC in chicken feed significantly improved the average daily intake and gain to feed ratio. Additionally, LL-EFLmC treatment resulted in a significant increase in serum IgG and intestinal mucus SIgA levels. Administration of LL-EFLmC was found to effectively suppress APEC-O78 infection and mitigate the expression of pro-inflammatory cytokines, including IL-1β, IL-12, IFN-γ, and TNF-α. Additionally, 16S rDNA sequencing data revealed that LL-EFLmC was able to restore the intestinal flora that had been disrupted by APEC-O78. These findings suggest that LL-EFLmC may serve as a promising feed additive and antibiotic alternative in chicken production, due to its potential to enhance immune regulation, promote growth, and confer resistance against APEC-O78 infection.