Robust Colonization of Nasal Microbiota Across the Respiratory Tract and the Gut Modulates Innate Immune Response in a Germ-Free Pig Model

The use of antibiotics in swine production has contributed to improved health and growth rates but also led to significant challenges, including the emergence of antibiotic-resistant bacteria and disruptions in the microbiome. This study employs a germ-free pig model to investigate the transplantation of the nasal microbiome into the respiratory tract, exploring its potential to colonize multiple body sites and its impact on host immunity. Using germ-free piglets inoculated with nasal microbiota from healthy donors, we examined the dynamics of microbial community formation across the respiratory and gastrointestinal tracts and assessed the effects of antibiotic intervention. Our findings reveal that specific taxa, predominantly from the phyla Proteobacteria and Firmicutes, cross colonized both respiratory as well as gastrointestinal tract. This cross- colonization highlights the adaptability of nasal microbiota and suggests a significant role in modulating host immunity through the gut-lung axis. The administration of the antibiotic tulathromycin on day 11 post-inoculation altered both nasal and gut microbiota compositions, reducing microbial diversity and impacting immune gene expression and cytokine profiles. These results underscore the complex interactions within the gut-lung axis and emphasize the implications of antibiotic use on microbial health and host immunity. Understanding these interactions provides crucial insights into alternative strategies for managing health in swine production without relying on antibiotics. Our study advocates for a reevaluation of antibiotic practices and supports the development of microbiome-centered interventions in swine health management.