Petit Fabienne, Clermont Olivier, Delannoy Sabine, Servais Pierre, Gourmelon Michèle, Fach Patrick, Oberlé Kenny, Fournier Matthieu, Denamur Erick, Berthe Thierry
Normandie Université, UniRouen, UniCaen, CNRS UMR M2CRouen, France.
Sorbonne Universités, UPMC, CNRS, EPHE, UMR 7619 METISParis, France.
Front Microbiol. 2017 Apr 18;8:609. doi: 10.3389/fmicb.2017.00609. eCollection 2017.
The aim of this study was to investigate the diversity of the population, focusing on the occurrence of pathogenic , in surface water draining a rural catchment. Two sampling campaigns were carried out in similar hydrological conditions (wet period, low flow) along a river continuum, characterized by two opposite density gradients of animals (cattle and wild animals) and human populations. While the abundance of slightly increased along the river continuum, the abundance of both human and ruminant-associated markers, as well as the number of multi-resistant to antibiotics, evidenced a fecal contamination originating from animals at upstream rural sites, and from humans at downstream urban sites. A strong spatial modification of the structure of the population was observed. At the upstream site close to a forest, a higher abundance of the B2 phylogroup and clade strains were observed. At the pasture upstream site, a greater proportion of both E and B1 phylogroups was detected, therefore suggesting a fecal contamination of mainly bovine origin. Conversely, in downstream urban sites, A, D, and F phylogroups were more abundant. To assess the occurrence of intestinal pathogenic strains, virulence factors [ (LT), (ST), and ] were screened among 651 isolates. Intestinal pathogenic strains STEC O174:H21 (2) and EHEC O26:H11 (1) were isolated in water and sediments close to the pasture site. In contrast, in the downstream urban site aEPEC/EAEC and DAEC of human origin, as well as extra-intestinal pathogenic belonging to clonal group A of D phylogroup, were sampled. Even if the estimated input of STEC (Shiga toxin-producing ) released in water at the upstream pasture site - at the downstream site was low, we show that STEC could persist in sediment. These results show that, the run-off of small cattle farms contributed, as much as the wastewater effluent, in the dissemination of pathogenic in both water and sediments, even if the microbiological quality of the water was good or to average quality according to the French water index.
本研究的目的是调查农村集水区地表水的种群多样性，重点关注致病微生物的出现情况。在类似水文条件下（丰水期、低流量）沿着河流连续体开展了两次采样活动，该河流连续体的特点是动物（牛和野生动物）和人类种群存在两个相反的密度梯度。虽然沿着河流连续体微生物的丰度略有增加，但人类和反刍动物相关微生物标记物的丰度以及对多种抗生素耐药的微生物数量，都证明上游农村地区的粪便污染源自动物，而下游城市地区的粪便污染源自人类。观察到微生物种群结构存在强烈的空间变化。在靠近森林的上游站点，观察到B2系统发育群和特定进化枝菌株的丰度较高。在牧场上游站点，检测到E和B1系统发育群的比例更大，因此表明主要是牛源粪便污染。相反，在下游城市站点，A、D和F系统发育群更为丰富。为了评估肠道致病菌株的出现情况，在651株微生物分离物中筛选了毒力因子[热不稳定毒素（LT）﹑热稳定毒素（ST）和志贺毒素]。在靠近牧场站点的水和沉积物中分离出肠道致病菌株肠出血性大肠杆菌O174:H21（2株）和肠产志贺毒素大肠杆菌O26:H11（1株）。相比之下，在下游城市站点采集到了人类源的非典型肠产毒素大肠杆菌/肠集聚性大肠杆菌和弥漫性黏附大肠杆菌，以及属于D系统发育群A克隆群的肠外致病性大肠杆菌。即使在上游牧场站点释放到水中的产志贺毒素大肠杆菌（STEC）估计输入量与下游站点相比很低，但我们表明STEC可以在沉积物中持续存在。这些结果表明，即使根据法国水指标水的微生物质量良好或为中等质量，小型养牛场的径流在水和沉积物中致病微生物的传播中所起的作用与废水排放一样大。
