Layer segmented filamentous bacteria colonize and impact gut health of broiler chickens

In commercial poultry farms, chicks hatch away from their progenitors from which they acquire key host-specific microbiota, like segmented filamentous bacteria (SFB) involved in gut maturation in early life. This study investigated whether providing chicken SFB to newly hatched broilers would increase their gut maturation and resistance to bacteria relevant to broiler and human health. One-day-old Ross308 broilers were orally treated with either phosphate-buffered saline (CON) or layer-derived SFB (D-SFB). On days 5, 10, 17, and 24, feces were collected to detect and enumerate SFB and <i>Enterobacteriaceae</i>. On days 8, 15, 22, and 29, birds were euthanized, intestinal samples were collected to detect and enumerate SFB through quantitative PCR (qPCR) and microscopy and expression of genes associated with gut immune function through reverse transcription-qPCR. This study showed that, despite their host specificity, layer SFB can colonize their genetically distinct relative broilers. Ileal SFB colonization was accelerated by a week with the SFB treatment and covered the proximal, medial, and distal sections of the ileum. Colonization of the ileum by SFB in early life highly activated gene expression of intestinal barrier proteins and cytokines, e.g., IL-10 and IFNγ but not IL-17. SFB treatment reduced the level of <i>Enterobacteriaceae</i> in the gut and provided superior resistance to intestinal and extraintestinal pathogens as tested <i>in vitro</i>. Overall, early gut colonization of SFB is imperative for the maturation of the gut immune system and the establishment of a homeostatic gut environment. Improving our understanding of gut immune maturation in food-producing animals is crucial for both human and animal health.IMPORTANCEIn commercial farms, newly hatched chicks may lack host-specific microbiota that help mature their gut immune system for lifelong health benefits. Here, introducing an avian segmented filamentous bacteria (SFB) to commercially sourced chickens orally at hatch accelerated SFB colonization of the ileum. Remarkably, SFB from layers were able to colonize broilers and enhance gut immune maturation, and this immunomodulation impacted the ability to increase intestinal and extraintestinal resistance to bacteria relevant to poultry and human health. With the antibiotic restrictions in animal production, strategies that will help mitigate infections are urgently needed. In summary, we developed a live prophylactic for newly hatched chicks to improve animal health and food safety. Due to the host specificity of SFB, our data highlight the importance of investigating the molecular mechanism of SFB interaction in their own host.