Xicohtencatl-Cortes Juan, Sánchez Chacón Ethel, Saldaña Zeus, Freer Enrique, Girón Jorge A
Department of Immunobiology, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, USA.
J Food Prot. 2009 Jul;72(7):1531-7. doi: 10.4315/0362-028x-72.7.1531.
Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen responsible for human diarrheal disease. EHEC lives in the intestinal tract of cattle and other farm and wild animals, which may be the source of environmental contamination particularly of agricultural fields. Human infections are associated with consumption of tainted animal products and fresh produce. How the bacteria interact with the plant phyllosphere and withstand industrial decontamination remain to be elucidated. The goals of the present study were to investigate the environmental conditions and surface structures that influence the interaction of EHEC O157:H7 with baby spinach and lettuce leaves in vitro. Independently of the production of Shiga toxin, EHEC O157:H7 colonizes the leaf surface via flagella and the type 3 secretion system (T3SS). Ultrastructural analysis of EHEC-infected leafy greens revealed the presence of flagellated bacteria, and mutation of the fliC flagellin gene in EHEC EDL933 rendered the bacteria significantly less adherent, suggesting the involvement of flagella in the bacteria-leaf interaction. EDL933 mutated in the escN (ATPase) gene associated with the function of the T3SS but not in the eae (intimin adhesin) gene required for adherence to host intestinal cells had significantly reduced adherence compared with that of the parental strain. The data suggest a compelling role of flagella and the T3SS in colonization of leafy green produce. Colonization of salad leaves by EHEC strains may be a strategy that ensures survival of these bacteria in the environment and allows transmission to the human host.
肠出血性大肠杆菌（EHEC）是一种食源性病原体，可导致人类腹泻疾病。EHEC存在于牛以及其他农场和野生动物的肠道中，这可能是环境污染的来源，尤其是对农田的污染。人类感染与食用受污染的动物产品和新鲜农产品有关。这种细菌如何与植物叶际相互作用以及如何耐受工业去污仍有待阐明。本研究的目的是调查在体外影响EHEC O157:H7与嫩菠菜和生菜叶相互作用的环境条件和表面结构。独立于志贺毒素的产生，EHEC O157:H7通过鞭毛和III型分泌系统（T3SS）定殖于叶片表面。对受EHEC感染的绿叶蔬菜进行超微结构分析，发现存在有鞭毛的细菌，并且EHEC EDL933中fliC鞭毛蛋白基因的突变使细菌的粘附力显著降低，这表明鞭毛参与了细菌与叶片的相互作用。与T3SS功能相关的escN（ATP酶）基因突变但与粘附宿主肠道细胞所需的eae（紧密粘附素）基因未突变的EDL933与亲本菌株相比，其粘附力显著降低。数据表明鞭毛和T3SS在绿叶蔬菜定殖中具有重要作用。EHEC菌株在沙拉叶上定殖可能是一种确保这些细菌在环境中生存并使其传播给人类宿主的策略。
