Systematic review of gut microbiota structural characteristics in patients with ischemic stroke

Background Emerging evidence implicates the gut microbiota (GM) in the pathogenesis of ischemic stroke (IS). However, systematic evaluations synthesizing evidence on microbial shifts, functional alterations, and clinical correlations are lacking. This study aimed to comprehensively analyze GM characteristics in IS patients versus healthy controls (HC). Methods A systematic search of PubMed, Web of Science, and Embase was conducted from inception to April 2025. Observational studies comparing GM in IS patients and HC were included. Data on alpha/beta diversity, relative microbial abundance (phylum to species), predicted functional pathways, and microbiota–clinical indicator correlations were extracted. A narrative synthesis summarized the direction and consistency of reported findings. Results Twenty-four studies involving 1,957 participants (1,159 IS, 798 HC) were included. The qualitative synthesis revealed no consistent differences in alpha diversity indices between IS and HC, while significant beta diversity separation was frequently reported (18/22 studies). At the phylum level, an increased relative abundance of Proteobacteria and a decreased abundance of Firmicutes were the most consistent findings in IS patients. Key genera frequently enriched in IS included Lactobacillus , Streptococcus , and Parabacteroides , while Faecalibacterium , Agathobacter , and Blautia were commonly depleted. LEfSe analysis confirmed these discriminative taxa. Predicted functional analysis suggested enrichment of pro-inflammatory pathways (e.g., lipopolysaccharide biosynthesis) and depletion of metabolic and neuroprotective pathways in IS. Clinically, Faecalibacterium abundance correlated negatively with NIHSS and mRS scores, while Lactobacillus and Streptococcus showed positive correlations with stroke severity and inflammatory markers. Conclusion Ischemic stroke is associated with distinct gut microbial dysbiosis characterized by a pro-inflammatory, opportunistic pathogen-enriched, and butyrate-producer-depleted profile. These alterations correlate with disease severity and are linked to predicted disruptions in microbial metabolic functions. However, whether this dysbiosis is a cause, consequence, or exacerbating factor of IS remains to be determined. The gut microbiota may serve as a potential biomarker and therapeutic target in ischemic stroke. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251117510 , identifier CRD420251117510.