Mechanisms and pathophysiology leading to development of small intestinal microbial dysbiosis

Small intestinal microbial dysbiosis (SIMD) is characterized by an aberrant expansion of microbial populations in the small intestine, predominantly bacteria, with occasional involvement of archaea or fungi. This condition typically arises secondary to perturbations in normal gastrointestinal physiology. Contributing factors include impaired intestinal motility, hypo- or achlorhydria, reduced bile or pancreatic enzyme secretion, anatomical alterations, and compromised mucosal or systemic immune defences.

The resulting microbial overgrowth can disrupt nutrient absorption, modulate local and systemic immune responses, and contribute to gastrointestinal symptomatology such as bloating, malabsorption, and chronic inflammation. Elucidating the underlying pathophysiological mechanisms of SIMD is essential for guiding targeted therapeutic strategies and optimizing patient management.

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https://www.thelancet.com/journals/langas/article/PIIS2468-1253(25)00295-X/abstract