CONTEXT: The intestinal microbiota and their metabolites play an important role in acute ischemic stroke (AIS) and modulate brain functions directly or indirectly through immune, endocrine, vagal, and other humoral pathways. However, relatively few investigations have evaluated the gut microbiome and its levels of inflammatory factors or the potential associations of those factors with stroke outcomes in patients who have had acute ischemic stroke (AIS), with different stroke severities. OBJECTIVE: The study intended to determine if AIS patients would have different gut microbiota and inflammatory-factor levels than healthy individuals and if those levels would be associated with the stroke's severity and the patient's prognosis. DESIGN: The research team performed a prospective observational study. SETTING: The study took place in the Department of Rehabilitation at the General Hospital of Wanbei Coal and Electricity Group, which is the Third Affiliated Hospital of Bengbu Medical College in Suzhou, Anhui, China. PARTICIPANTS: Participants were 90 patients who had received a diagnosis and treatment of AIS within 48 hours of the stroke's onset at the hospital, between October 2021 and March 2022. GROUPS: The research team performed multiple comparisons of the baseline demographic and clinical characteristics, the gut microbiota, and levels of inflammatory factors of a number of groups: (1) the AIS patients, the AIS group, to the healthy controls, the control group; (2) the AIS participants who had had a mild or moderate stroke, the mild-moderate group, and those who had had a severe stroke, the severe group; (3) the AIS participants who had had a good primary outcome, the good outcome group, and those who had had a poor primary outcome, the poor outcome group; (4) the mild-moderate and severe groups to the control group; and (5) the good outcome and poor outcome groups to the control group. OUTCOME MEASURES: The research team: (1) obtained participants' fecal samples within 72 hours of admission; (2) collected baseline data for the included AIS patients and controls; (3) used 16S rRNA gene sequencing and an enzyme-linked immunosorbent assay (ELISA) to compare the fecal microbial compositions, lipopolysaccharide (LPS) contents, and inflammatory-factor levels between groups; and (4) evaluated the associations of the fecal microbial compositions with severity of stroke and 90-day functional outcomes, using logistic-regression models. RESULTS: The gut microflora distinguished AIS patients from healthy controls. The LPS and inflammatory-factor levels were associated with an increased risk of poor functional outcomes at day 90. CONCLUSIONS: Dysbiosis of gut microbiota and LPS and inflammatory-factor levels can increase AIS patients' subsequent risks for poor functional outcomes, indicating that the dysbiosis and levels could be potential prognostic markers and therapeutic targets for stroke.