Strategically isolated bacteriophages targeting ETEC K88 (F4) alleviate post-weaning diarrhea in piglets via modulation of gut microbiota and inflammatory responses.

backgroundPost-weaning diarrhea (PWD) in piglets, primarily caused by enterotoxigenic Escherichia coli (ETEC) K88 (F4) infection, presents a major challenge in swine production. This study aimed to isolate bacteriophages (phages) specific to ETEC K88, utilizing ETEC K88 as the host strain, and to assess the efficacy of dietary supplementation with the isolated phages in weaned piglets over a two-week period using an ETEC K88 challenge model in a pilot study.

resultsThree ETEC K88-specific phages (EC-P1, EC-P2, and EC-P3) were isolated and identified as tailed phages. These phages displayed a short latency period, broad acid-base stability, and thermal stability, effectively inhibiting ETEC K88 growth and disrupting ETEC K88 biofilms in vitro. Lyophilized phage powder was prepared and supplemented at 400, 600 or 800 mg/kg in the diets. Compared to the ETEC K88 group, piglets in the ETEC K88 + 600 or 800 mg/kg phages group exhibited markedly lower diarrhea scores and rectal temperatures at 12, 24, and 48 h post-infection. Supplementation with 600 mg/kg phages enhanced intestinal integrity of ETEC K88-infected piglets, as evidenced by an increased jejunal villus height and villus height-to-crypt depth ratio, reduced serum diamine oxidase and D-lactate levels, and upregulated jejunal ZO-1 protein expression. Concomitantly, systemic and jejunal inflammatory responses were attenuated by supplementation with 600 mg/kg of phages, as evidenced by decreased serum LPS, IL-1β, IL-10 and TNF-α levels, down-regulated jejunal IL-1β and IL-6 mRNA expression, and suppressed NF-κB signalling (downregulated p-IκBα/IκBα and p-p65/p65 ratios). Supplementation with 600 mg/kg phages also shifted the faecal microbiota toward eubiosis, increasing the Shannon index, decreasing Proteobacteria and Enterobacteriaceae abundances, and elevating beneficial taxa (Patescibacteria, Muribaculaceae, and Subdoligranulum). Correlation analysis further revealed that Proteobacteria and Enterobacteriaceae abundances were positively associated with diarrhoea characteristics, whereas Muribaculaceae showed a negative correlation.

conclusionsThree ETEC K88-targeting phages were successfully isolated, characterized, and prepared as lyophilized phage powder for dietary supplementation. Dietary supplementation with 600 mg/kg of lyophilized phage powder alleviated PWD in piglets by modulating gut microbiota and inflammatory responses.