Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada N5V 4T3.
Appl Environ Microbiol. 2010 Mar;76(5):1486-96. doi: 10.1128/AEM.02288-09. Epub 2009 Dec 28.
We investigated the prevalence and diversity of Escherichia coli strains isolated from surface waters from multiple watersheds within the South Nation River basin in eastern Ontario, Canada. The basin is composed of mixed but primarily agricultural land uses. From March 2004 to November 2007, a total of 2,004 surface water samples were collected from 24 sampling sites. E. coli densities ranged from undetectable to 1.64 x 10(5) CFU 100 ml(-1) and were correlated with stream order and proximity to livestock production systems. The diversity of 21,307 E. coli isolates was characterized using repetitive extragenic palindromic PCR (rep-PCR), allowing for the identification of as many as 7,325 distinct genotypes, without capturing all of the diversity. The community was temporally and spatially dominated by a few dominant genotypes (clusters of more than 500 isolates) and several genotypes of intermediary abundance (clustering between 10 and 499 isolates). Simpson diversity indices, assessed on a normalized number of isolates per sample, ranged from 0.050 to 0.668. Simpson indices could be statistically discriminated on the basis of year and stream order, but land use, discharge, weather, and water physical-chemical properties were not statistically important discriminators. The detection of Campylobacter species was associated with statistically lower Simpson indices (greater diversity; P < 0.05). Waterborne E. coli isolates from genotypes of dominant and intermediary abundance were clustered with isolates obtained from fecal samples collected in the study area over the same period, and 90% of the isolates tested proved to share genotypes with fecal isolates. Overall, our data indicated that the densities and distribution of E. coli in these mixed-use watersheds were linked to stream order and livestock-based land uses. Waterborne E. coli populations that were distinct from fecal isolates were detected and, on this basis, were possibly naturalized E. coli strains.
我们调查了加拿大安大略省东部分布在南国民河盆地多个流域的地表水中分离出的大肠杆菌菌株的流行情况和多样性。该流域由混合但主要是农业用地组成。从 2004 年 3 月到 2007 年 11 月，从 24 个采样点共采集了 2004 个地表水样本。大肠杆菌密度从不可检测到 1.64 x 10(5)CFU 100 ml(-1)不等，与溪流等级和靠近牲畜生产系统有关。使用重复基因外回文 PCR（rep-PCR）对 21307 个大肠杆菌分离株的多样性进行了表征，允许鉴定多达 7325 个不同的基因型，而没有捕获所有的多样性。该群落由少数优势基因型（超过 500 个分离株的聚类）和几个中等丰度的基因型（10 到 499 个分离株之间的聚类）在时间和空间上占主导地位。基于样本中归一化的分离株数量评估的 Simpson 多样性指数范围为 0.050 至 0.668。基于年和溪流等级可以对 Simpson 指数进行统计学区分，但土地利用、排放、天气和水的物理化学性质不是统计学上重要的区分因素。弯曲杆菌种的检测与统计学上较低的 Simpson 指数（更多的多样性；P < 0.05）相关。从同一时期在研究区域收集的粪便样本中分离出的优势和中等丰度基因型的水源性大肠杆菌分离株与分离株聚类，90%的分离株经测试证明与粪便分离株共享基因型。总体而言，我们的数据表明，这些混合用途流域中大肠杆菌的密度和分布与溪流等级和以牲畜为基础的土地利用有关。从粪便分离株中检测到与粪便分离株不同的水源性大肠杆菌种群，并且在此基础上，这些种群可能是自然化的大肠杆菌菌株。
