ABSTRACT

Colibactin is synthesized by a 54-kb genomic island, leads to toxicity in eukaryotic cells, and plays a vital role in many diseases, including neonatal sepsis and meningitis. Avian pathogenic Escherichia coli (APEC) is speculated to be an armory of extraintestinal pathogenic Escherichia coli and can be a potential zoonotic bacterium that threatens human and animal health. In this study, the APEC XM meningitis mouse model was successfully established to investigate the effect of colibactin in in vivo infection. The clbH-deletion mutant strain induced lower γ-H2AX expression, no megalocytosis, and no cell cycle arrest in bEnd.3 cells, which showed that the deletion of clbH decreased the production of colibactin in the APEC XM strain. The deletion of clbH did not affect the APEC XM strain’s ability of adhering to and invading bEnd.3 cells. In vitro, the non-colibactin-producing strain displayed significantly lower serum resistance and it also induced a lower level of cytokine mRNA and few disruptions of tight junction proteins in infected bEnd.3 cells. Meningitis did not occur in APEC ΔclbH-infected mice in vivo, who showed fewer clinical symptoms and fewer lesions on radiological and histopathological analyses. Compared with the APEX XM strain, APEC ΔclbH induced lower bacterial colonization in tissues, lower mRNA expression of cytokines in brain tissues, and slight destruction of the brain blood barrier. These results indicate that clbH is a necessary component for the synthesis of genotoxic colibactin, and colibactin is related to the development of meningitis induced by APEC XM.

摘要

Colibactin 由一个 54-kb 的基因组岛合成，在真核细胞中产生毒性，并在包括新生儿败血症和脑膜炎在内的许多疾病中发挥重要作用。据推测，禽类致病性大肠杆菌（APEC）是一种肠道外致病性大肠杆菌，可能是一种威胁人类和动物健康的潜在人畜共患细菌。本研究成功建立APEC XM脑膜炎小鼠模型，研究大肠杆菌素对体内感染的影响。clbH缺失突变株诱导bEnd.3细胞中γ-H2AX表达降低，无巨细胞增多，无细胞周期停滞，表明clbH缺失减少了 APEC XM 菌株中大肠杆菌素的产生。clbH的缺失不影响APEC XM株粘附和侵入bEnd.3细胞的能力。在体外，不产生大肠杆菌素的菌株显示出显着降低的血清抗性，并且它还诱导了较低水平的细胞因子 mRNA，并且在受感染的 bEnd.3 细胞中紧密连接蛋白的破坏很少。体内感染 APEC Δ clbH的小鼠未发生脑膜炎，这些小鼠在放射学和组织病理学分析中表现出较少的临床症状和较少的病变。与 APEX XM 菌株相比，APEC Δ clbH诱导组织中较低的细菌定植，脑组织中细胞因子的mRNA表达降低，以及脑血屏障的轻微破坏。这些结果表明，clbH是合成遗传毒性大肠杆菌素的必要成分，大肠杆菌素与APEC XM诱发的脑膜炎的发生有关。