A native probiotic strain Enterococcus faecalis TMBC 10513 alleviates avian pathogenic Escherichia coli-induced growth impairment and intestinal disruptions in yellow-feathered broilers at the early stage of infection.

This study aimed to probe if a native probiotic Enterococcus faecalis TMBC 10513 could protect the growth and intestinal health of yellow-feathered broilers against avian pathogenic Escherichia coli (APEC) challenge. In vitro bacteriostasis of E. faecalis TMBC 10513 against APEC O1 was initially investigated. Subsequently, 240 one-day-old yellow-feathered female broilers were divided into three groups (eight replicates/group): control group, APEC group (received APEC O1 challenge at 7, 8 and 9 d of age) and EF group (APEC-challenged broilers supplemented with 5 × 10⁸ CFU/kg of E. faecalis TMBC 10513). Parameters were measured at one day post the last gavage (namely d 10). The results revealed that E. faecalis inhibited (P < 0.05) APEC O1 growth and its adhesion to enterocytes. E. faecalis addition alleviated APEC-induced decreases (P < 0.05) in average daily weight gain, average daily feed intake and serum immunoglobulins levels, accompanied by an increase (P < 0.05) in spleen index of broilers. It also attenuated APEC-induced elevations (P < 0.05) in serum d-lactic acid and diamine oxidase levels, together with reductions (P < 0.05) in ileal villus height of broilers. Moreover, E. faecalis addition elevated (P < 0.05) ileal tight junction proteins (ZO-1, Occludin and Claudin-1) and certain cytokines (IL-1β and IL-8) expression, as well as reduced (P < 0.05) ileal APEC O1 amount in APEC-challenged broilers. Remarkably, E. faecalis addition enriched several beneficial bacteria (e.g. Bacteroidota, Actinobacteriota and multiple probiotic candidates) and reduced certain harmful bacteria (e.g. Proteobacteria and Escherichia-Shigella) in the cecum. It also lowered (P < 0.05) the expression of multiple virulence genes of cecal Escherichia. In conclusion, native E. faecalis alleviated APEC-induced intestinal disruptions of broilers at the early stage of infection by directly inhibiting this pathogen as well as improving intestinal immune responses and microbial community, thereby contributing to mitigate the observed growth impairment in APEC-challenged broilers. These findings supply a novel perception into the application of E. faecalis in restricting APEC infection in chicken production.