目的 探讨重性抑郁障碍（MDD）患者肠道菌群特征与选择性5-羟色胺再摄取抑制剂（SSRIs）疗效的关联性, 筛选可预测SSRIs疗效的肠道菌群生物标志物。方法 选取2024年5月—2025年5月宁夏回族自治区人民医院收治的90例MDD患者, 根据SSRIs治疗8周后疗效分为应答组56例和无应答组34例, 并选择30例健康对照, 采集基线粪便样本进行16S rRNA基因测序, 分析肠道菌群α多样性、菌属相对丰度差异,并通过相关性分析、多因素Logistic回归及ROC曲线评估菌群标志物对SSRIs疗效的预测价值。结果 MDD患者肠道菌群Chao1指数、Shannon指数低于健康对照（P<0.05）, 应答组与无应答组α多样性无差异（P>0.05）。应答组基线Blautia、双歧杆菌属、粪球菌属丰度高于无应答组（P<0.05）, 大肠杆菌-志贺菌属丰度低于无应答组（P<0.05）。基线Blautia、双歧杆菌属、粪球菌属丰度与SSRIs治疗8周HAMD-17减分率呈正相关（r分别为0.390、0.420、0.350,均P<0.05）, 三者联合预测SSRIs疗效的ROC曲线下面积（AUC）为0.910（灵敏度83.9%,特异度85.3%）。结论 MDD患者存在肠道菌群结构异常, 基线Blautia、双歧杆菌属、粪球菌属丰度可作为SSRIs疗效的潜在预测标志物,为MDD个体化治疗提供实验依据。

       Objective To explore the association between gut microbiota characteristics and the efficacy of selective serotonin reuptake inhibitors（SSRIs）in patients with major depressive disorder（MDD）, and to screen gut microbiota biomarkers for predicting SSRIs efficacy．Methods A total of 90 MDD patients（divided into responders[n=56] and non-responders[n=34] based on 8-week SSRIs efficacy）and 30 healthy controls were enrolled from May 2024 to May 2025．Fecal samples were collected for 16S rRNA gene sequencing to analyze gut microbiota α diversity and genus-level relative abundance．Correlation analysis, multivariate logistic regression, and receiver operating characteristic curve were used to evaluate the predictive value of microbiota markers for SSRIs efficacy．Results The Chao1 and Shannon indices of gut microbiota in MDD patients were significantly lower than those in healthy controls（P<0.05）, with no difference between responders and non-responders（P>0.05）．Responders had higher baseline abundances of Blautia,Bifidobacterium, and Coprococcus（P<0.05）, and lower abundance of Escherichia-Shigella compared to non-responders．Baseline abundances of Blautia,Bifidobacterium（P<0.05）, and Coprococcus were positively correlated with 8-week HAMD-17 reduction rate（r=0.390, 0.420, 0.350; all P<0.05）．The combined prediction of these three genera for SSRIs efficacy showed an area under the curve of 0.910（sensitivity 83.9%, specificity 85.3%）．Conclusions MDD patients exhibit abnormal gut microbiota structure．Baseline abundances of Blautia,Bifidobacterium, and Coprococcus may serve as potential predictive biomarkers for SSRIs efficacy, providing experimental basis for personalized treatment of MDD．