Gut-lung axis perturbation and Bifidobacterium potential after spinal cord injury in humans and mice.

Spinal cord injury (SCI) predisposes patients to severe respiratory complications. Integrating clinical observations with a mouse model, we identified gut-lung axis perturbation as a key mechanism. SCI increased the similarity between gut and lung microbial communities, consistent with cross-compartment convergence driven by intestinal dysbiosis. Fecal microbiota transplantation from SCI donors reproduced this convergence in healthy recipients. Crucially, oral Bifidobacterium supplementation restored intestinal community structure, reduced gut-lung similarity, and attenuated pulmonary inflammation following an Escherichia coli challenge. These findings indicate that SCI disrupts gut-lung compartmentalization and that augmenting beneficial gut taxa mitigates downstream pulmonary consequences. Microbiota-targeted strategies therefore warrant evaluation as adjuncts to reduce post-SCI respiratory risk.