National Food Institute, Division of Microbiology and Risk Assessment, Technical University of Denmark, Moerkhoej Bygade, Soeborg, Denmark.
Benef Microbes. 2010 Sep;1(3):271-81. doi: 10.3920/BM2010.0016.
Certain indigestible carbohydrates, known as prebiotics, are claimed to be beneficial for gut health through a selective stimulation of certain gut microbes including bifidobacteria. However, stimulation of such microbes does not necessarily imply a preventive effect against pathogen infection. We recently demonstrated a reduced resistance to Salmonella infection in mice fed diets containing fructo-oligosaccharides (FOS) or xylo-oligosaccharides (XOS). In the present study, faecal and caecal samples from the same mice were analysed in order to study microbial changes potentially explaining the observed effects on the pathogenesis of Salmonella. Denaturing gradient gel electrophoresis revealed that the microbiota in faecal samples from mice fed FOS or XOS were different from faecal samples collected before the feeding trial as well as from faecal profiles generated from control animals. This difference was not seen for caecal profiles. Further analysis of faecal samples by real-time PCR demonstrated a significant increase in the Bacteroidetes phylum, the Bacteroides fragilis group and in Bifidobacterium spp. in mice fed FOS or XOS. The observed bifidogenic effect was more pronounced for XOS than for FOS. The Firmicutes phylum and the Clostridium coccoides group were reduced by both FOS and XOS. Surprisingly, no significant differences were detected between faecal samples collected before and after pathogen challenge in any of the groups. Furthermore, no effect of diets on caecal concentrations of short-chain fatty acids was recorded. In conclusion, diets supplemented with FOS or XOS induced a number of microbial changes in the faecal microbiota of mice. The observed effects of XOS were qualitatively similar to those of FOS, but the most prominent bifidogenic effect was seen for XOS. An increased level of bifidobacteria is thus not in itself preventive against Salmonella infection, since the same XOS or FOS-fed mice were previously reported to be more severely affected by Salmonella than control animals.
某些难以消化的碳水化合物，被称为益生元，据称通过选择性刺激某些肠道微生物，包括双歧杆菌，对肠道健康有益。然而，对这些微生物的刺激并不一定意味着对病原体感染有预防作用。我们最近证明，在喂食含有低聚果糖（FOS）或木低聚糖（XOS）的饮食的小鼠中，对沙门氏菌感染的抵抗力降低。在本研究中，分析了来自同一批小鼠的粪便和盲肠样本，以研究可能解释观察到的对沙门氏菌发病机制影响的微生物变化。变性梯度凝胶电泳显示，喂食 FOS 或 XOS 的小鼠粪便样本中的微生物群与喂养试验前收集的粪便样本以及来自对照动物的粪便谱不同。盲肠样本没有出现这种差异。通过实时 PCR 对粪便样本进行的进一步分析表明，喂食 FOS 或 XOS 的小鼠的拟杆菌门、脆弱拟杆菌组和双歧杆菌属显著增加。XOS 的双歧杆菌生成效果比 FOS 更为明显。厚壁菌门和梭状芽胞杆菌组被 FOS 和 XOS 减少。令人惊讶的是，在任何一组中，在病原体挑战前后收集的粪便样本之间都没有检测到显著差异。此外，饮食对盲肠短链脂肪酸浓度没有影响。总之，补充 FOS 或 XOS 的饮食会引起小鼠粪便微生物群中许多微生物变化。XOS 的观察到的作用与 FOS 的作用相似，但 XOS 表现出最明显的双歧杆菌生成作用。双歧杆菌水平的增加本身并不能预防沙门氏菌感染，因为之前报道 XOS 或 FOS 喂养的小鼠比对照动物更容易受到沙门氏菌感染。
