Background & Aims

Campylobacter jejuni, a prevalent foodborne bacterial pathogen, exploits the host innate response to induce colitis. Little is known about the roles of microbiota in C jejuni–induced intestinal inflammation. We investigated interactions between microbiota and intestinal cells during C jejuni infection of mice.

Methods

Germ-free C57BL/6 Il10^−/− mice were colonized with conventional microbiota and infected with a single dose of C jejuni (10⁹ colony-forming units/mouse) via gavage. Conventional microbiota were cultured under aerobic, microaerobic, or anaerobic conditions and orally transplanted into germ-free Il10^−/− mice. Colon tissues were collected from mice and analyzed by histology, real-time polymerase chain reaction, and immunoblotting. Fecal microbiota and bile acids were analyzed with 16S sequencing and high-performance liquid chromatography with mass spectrometry, respectively.

Results

Introduction of conventional microbiota reduced C jejuni–induced colitis in previously germ-free Il10^−/− mice, independent of fecal load of C jejuni, accompanied by reduced activation of mammalian target of rapamycin. Microbiota transplantation and 16S ribosomal DNA sequencing experiments showed that Clostridium XI, Bifidobacterium, and Lactobacillus were enriched in fecal samples from mice colonized with microbiota cultured in anaerobic conditions (which reduce colitis) compared with mice fed microbiota cultured under aerobic conditions (susceptible to colitis). Oral administration to mice of microbiota-derived secondary bile acid sodium deoxycholate, but not ursodeoxycholic acid or lithocholic acid, reduced C jejuni–induced colitis. Depletion of secondary bile acid–producing bacteria with antibiotics that kill anaerobic bacteria (clindamycin) promoted C jejuni–induced colitis in specific pathogen-free Il10^−/− mice compared with the nonspecific antibiotic nalidixic acid; colitis induction by antibiotics was associated with reduced level of luminal deoxycholate.

Conclusions

We identified a mechanism by which the microbiota controls susceptibility to C jejuni infection in mice, via bacteria-derived secondary bile acids.

中文翻译：

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微生物群衍生的代谢因子可减少小鼠弯曲菌病。

 背景与目标

空肠弯曲杆菌是一种常见的食源性细菌病原体，利用宿主的先天反应诱发结肠炎。关于微生物群在空肠弯曲菌诱导的肠道炎症中的作用知之甚少。我们研究了小鼠空肠弯曲菌感染期间微生物群与肠道细胞之间的相互作用。

 方法

无菌C57BL/6 Il10 ^-/−小鼠被常规微生物群定植，并通过管饲法感染单剂量空肠弯曲菌（10 ⁹菌落形成单位/小鼠）。常规微生物群在需氧、微需氧或厌氧条件下培养，并经口移植到无菌的Il10 ^−/−小鼠中。从小鼠身上收集结肠组织，并通过组织学、实时聚合酶链反应和免疫印迹进行分析。分别采用 16S 测序和高效液相色谱质谱法对粪便微生物群和胆汁酸进行分析。

 结果

传统微生物群的引入减少了先前无菌的Il10 ^−/−小鼠中空肠弯曲菌诱发的结肠炎，与空肠弯曲菌的粪便负荷无关，同时减少了哺乳动物雷帕霉素靶标的激活。微生物群移植和 16S 核糖体 DNA 测序实验表明，与喂养有氧条件下培养的微生物群（易患结肠炎）的小鼠相比，厌氧条件下培养的微生物群（可减少结肠炎）定植的小鼠的粪便样本中梭状芽胞杆菌 XI、双歧杆菌和乳杆菌含量更高。给小鼠口服源自微生物群的次级胆汁酸脱氧胆酸钠，而不是熊去氧胆酸或石胆酸，可以减少空肠弯曲菌诱发的结肠炎。与非特异性抗生素萘啶酸相比，用杀死厌氧菌的抗生素（克林霉素）消除产生次级胆汁酸的细菌，可促进无特定病原体的Il10 ^−/−小鼠空肠弯曲菌诱发的结肠炎；抗生素诱导的结肠炎与管腔脱氧胆酸水平降低有关。

 结论

我们确定了微生物群通过细菌衍生的次级胆汁酸控制小鼠对空肠弯曲菌感染的易感性的机制。