Center for Global Health; Division of Infectious Diseases and International Health; School of Medicine; University of Virginia; Charlottesville, VA USA; Institute of Biomedicine; Federal University of Ceará; Fortaleza, CE Brazil.
Virulence. 2013 Oct 1;4(7):624-33. doi: 10.4161/viru.26120. Epub 2013 Aug 19.
Enteroaggregative Escherichia coli (EAEC) is a major pathogen worldwide, associated with diarrheal disease in both children and adults, suggesting the need for new preventive and therapeutic treatments. We investigated the role of the micronutrient zinc in the pathogenesis of an E. coli strain associated with human disease. A variety of bacterial characteristics-growth in vitro, biofilm formation, adherence to IEC-6 epithelial cells, gene expression of putative EAEC virulence factors as well as EAEC-induced cytokine expression by HCT-8 cells-were quantified. At concentrations (≤ 0.05 mM) that did not alter EAEC growth (strain 042) but that are physiologic in serum, zinc markedly decreased the organism's ability to form biofilm (P<0.001), adhere to IEC-6 epithelial cells (P<0.01), and express putative EAEC virulence factors (aggR, aap, aatA, virK) (P<0.03). After exposure of the organism to zinc, the effect on virulence factor generation was prolonged (> 3 h). Further, EAEC-induced IL-8 mRNA and protein secretion by HCT-8 epithelial cells were significantly reduced by 0.05 mM zinc (P<0.03). Using an in vivo murine model of diet-induced zinc-deficiency, oral zinc supplementation (0.4 µg/mouse daily) administered after EAEC challenge (10 (10) CFU/mouse) significantly abrogated growth shortfalls (by>90%; P<0.01); furthermore, stool shedding was reduced (days 9-11) but tissue burden of organisms in the intestine was unchanged. These findings suggest several potential mechanisms whereby physiological levels of zinc alter pathogenetic events in the bacterium (reducing biofilm formation, adherence to epithelium, virulence factor expression) as well as the bacterium's effect on the epithelium (cytokine response to exposure to EAEC) to alter EAEC pathogenesis in vitro and in vivo. These effects may help explain and extend the benefits of zinc in childhood diarrhea and malnutrition.
肠聚集性大肠杆菌（EAEC）是一种全球性的主要病原体，与儿童和成人的腹泻病有关，这表明需要新的预防和治疗方法。我们研究了微量营养素锌在与人类疾病相关的大肠杆菌菌株发病机制中的作用。我们量化了各种细菌特性，包括体外生长、生物膜形成、IEC-6 上皮细胞粘附、推定 EAEC 毒力因子的基因表达以及 EAEC 诱导的 HCT-8 细胞细胞因子表达。在不改变 EAEC 生长（菌株 042）但在血清中具有生理意义的浓度（≤0.05 mM）下，锌显著降低了该生物体形成生物膜的能力（P<0.001），粘附到 IEC-6 上皮细胞（P<0.01），并表达推定的 EAEC 毒力因子（aggR、aap、aatA、virK）（P<0.03）。在生物体暴露于锌后，对毒力因子生成的影响持续时间延长（>3 h）。此外，0.05 mM 锌显著降低了 EAEC 诱导的 HCT-8 上皮细胞 IL-8 mRNA 和蛋白分泌（P<0.03）。在饮食诱导锌缺乏的体内小鼠模型中，在 EAEC 挑战（10（10）CFU/小鼠）后给予口服锌补充剂（0.4 µg/小鼠/天）可显著消除生长不足（>90%；P<0.01）；此外，粪便脱落减少（第 9-11 天），但肠道内生物体的组织负担不变。这些发现表明，生理水平的锌通过几种潜在机制改变细菌中的致病事件（减少生物膜形成、上皮细胞粘附、毒力因子表达）以及细菌对上皮细胞的影响（暴露于 EAEC 时细胞因子的反应），从而改变体外和体内的 EAEC 发病机制。这些影响可能有助于解释和扩展锌在儿童腹泻和营养不良中的益处。
