Children with inflammatory bowel diseases (IBD) are particularly vulnerable to infection with Clostridioides difficile (CDI). IBD and IBD + CDI have overlapping symptoms but respond to distinctive treatments, highlighting the need for diagnostic biomarkers. Here, we studied pediatric patients with IBD and IBD + CDI, comparing longitudinal data on the gut microbiome, metabolome, and other measures. The microbiome is dysbiotic and heterogeneous in both disease states, but the metabolome reveals disease-specific patterns. The IBD group shows increased concentrations of markers of inflammation and tissue damage compared with healthy controls, and metabolic changes associate with susceptibility to CDI. In IBD + CDI, we detect both metabolites associated with inflammation/tissue damage and fermentation products produced by C. difficile. The most discriminating metabolite found is isocaproyltaurine, a covalent conjugate of a distinctive C. difficile fermentation product (isocaproate) and an amino acid associated with tissue damage (taurine), which may be useful as a joint marker of the two disease processes.

患有炎症性肠病 (IBD) 的儿童特别容易感染艰难梭菌(CDI)。IBD 和 IBD + CDI 有重叠的症状，但对独特的治疗有反应，突出了对诊断生物标志物的需求。在这里，我们研究了患有 IBD 和 IBD + CDI 的儿科患者，比较了肠道微生物组、代谢组和其他指标的纵向数据。在这两种疾病状态下，微生物组都是失调的和异质的，但代谢组揭示了疾病特异性模式。与健康对照组相比，IBD 组的炎症和组织损伤标志物浓度增加，代谢变化与 CDI 易感性相关。在 IBD + CDI 中，我们检测到与炎症/组织损伤相关的代谢物和艰难梭菌产生的发酵产物. 发现的最具鉴别力的代谢物是异己酰牛磺酸，一种独特的艰难梭菌发酵产物（异己酸盐）和与组织损伤相关的氨基酸（牛磺酸）的共价结合物，可用作两种疾病过程的联合标志物。