Background Campylobacter colonise the gastrointestinal tract of warm-blooded animals and are major enteropathogens in humans. C. coli is less common than C. jejuni and accounts for about 10% of the total number of Campylobacter infections although the two species seem to share many virulence determinants. Campylobacter bacteraemia is rare, estimated to occur in less than 1% of the infections, and the exact mechanisms regulating the progression of the infection from the gastrointestinal tract to the blood stream are unclear. Here, we looked at the contribution of C. coli to Campylobacter infections and further compared various virulence traits in C. coli clade 1 blood and stool isolates. Results We assessed the numbers of C. jejuni and C. coli among typed isolates in the PubMLST database and found that C. coli accounted for 25.9% of blood isolates, but only 8.9% of the stool isolates. Phylogenetic analysis of 128 C. coli clade 1 whole genome sequences deposited to NCBI revealed no specific clustering of the human blood, stool or animal isolates. Of the six C. coli isolates chosen for phenotypic analyses, stool isolates adhered significantly better to human HT-29 colon cancer cells than the blood isolates, while there was no difference in induced IL-8 levels between the isolates. Furthermore, the stool isolates had two- to fourfold higher RNA expression levels of the flpA, ciaB, iamA and cdt virulence genes than the blood isolates. Finally, we looked at the gene structure of the cdtA, B and C toxin genes and found numerous nucleotide additions and deletions disrupting the open reading frames. In contrast to 58% isolates of animal origin, only 38% and 32% of human blood and stool isolates, respectively, had all three cdt genes intact, a prerequisite to produce functional toxins. Conclusions This study reveals interesting differences between C. coli clade 1 isolates of human and animal origin on one hand, and also between human blood and stool isolates, on the other. The results suggest that C. coli might downregulate and/or inactivate various virulence determinants as the isolates pass from the animal host to the human gastrointestinal tract and enter the human blood stream.

中文翻译：

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人血液和粪便弯曲杆菌分支 1 ST828CC 分离株毒力基因表达的差异。

背景弯曲杆菌定植于温血动物的胃肠道中，是人类的主要肠道病原体。大肠杆菌不如空肠弯曲菌常见，约占弯曲杆菌感染总数的 10%，尽管这两个物种似乎有许多共同的毒力决定因素。弯曲杆菌菌血症很少见，估计发生在不到 1% 的感染中，并且调节感染从胃肠道到血流进展的确切机制尚不清楚。在这里，我们研究了大肠杆菌对弯曲杆菌感染的贡献，并进一步比较了大肠杆菌分支 1 血液和粪便分离株的各种毒力特征。结果我们评估了 PubMLST 数据库中分型分离株中空肠弯曲菌和大肠杆菌的数量，发现大肠杆菌占血液分离株的 25.9%，但仅占粪便分离株的 8.9%。对 NCBI 保藏的 128 个大肠杆菌进化枝 1 全基因组序列进行的系统发育分析显示，人类血液、粪便或动物分离株没有特定的聚类。在选择用于表型分析的六种大肠杆菌分离株中，粪便分离株对人 HT-29 结肠癌细胞的粘附明显优于血液分离株，而分离株之间诱导的 IL-8 水平没有差异。此外，粪便分离株的 flpA、ciaB、iamA 和 cdt 毒力基因的 RNA 表达水平比血液分离株高出两到四倍。最后，我们研究了 cdtA、B 和 C 毒素基因的基因结构，发现大量核苷酸添加和缺失破坏了开放阅读框。与 58% 的动物来源分离株相比，只有 38% 和 32% 的人类血液和粪便分离株分别具有完整的所有三个 cdt 基因，这是产生功能性毒素的先决条件。结论 这项研究一方面揭示了人类和动物来源的大肠杆菌进化枝 1 分离株之间的有趣差异，另一方面也揭示了人类血液和粪便分离株之间的有趣差异。结果表明，当分离株从动物宿主传播到人类胃肠道并进入人类血流时，大肠杆菌可能下调和/或灭活各种毒力决定因素。