Probiotic therapeutics: A critical review of mechanisms, clinical efficacy, and the frontier of precision microbiome modulation.

Probiotic therapeutics are evolving from generalized wellness supplements to precision Live Biotherapeutic Products aimed at specific disease targets. This review elucidates the multi-layered mechanistic framework of probiotic action, which spans ecological niche modulation, epithelial barrier reinforcement, and systemic signaling via the gut-brain axis. While clinical efficacy is established for conditions like antibiotic-associated diarrhea, trial outcomes remain highly heterogeneous for complex disorders such as irritable bowel syndrome and metabolic syndrome. We deconstruct this variability, attributing it to critical factors often overlooked in study design: stringent strain-specificity, host-specific colonization resistance, and the lack of standardized core outcome sets. The field is now advancing toward precision microbiome modulation through next-generation biotics like Akkermansia muciniphila, synbiotics, and engineered microbial therapeutics. We conclude that integrating multi-omics technologies with artificial intelligence is essential to transition from empirical supplementation to personalized, evidence-based clinical practice.