Wilkes Graham, Edge Thomas, Gannon Victor, Jokinen Cassandra, Lyautey Emilie, Medeiros Diane, Neumann Norman, Ruecker Norma, Topp Edward, Lapen David R
Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.
Water Res. 2009 May;43(8):2209-23. doi: 10.1016/j.watres.2009.01.033. Epub 2009 Feb 11.
The South Nation River basin in eastern Ontario, Canada is characterized by mixed agriculture. Over 1600 water samples were collected on a bi-weekly basis from up to 24 discrete sampling sites on river tributaries of varying stream order within the river basin between 2004 and 2006. Water samples were analyzed for: densities of indicator bacteria (Escherichia coli, Clostridium perfringens, enterococci, total and fecal coliforms), the presence of pathogenic bacteria (Listeria monocytogenes, E. coli O157:H7, Salmonella spp., Campylobacter spp.), and densities of parasite Giardia cysts and Cryptosporidium oocysts. Relationships between indicator bacteria, pathogens, and parasite oocysts/cysts were overall weak, seasonally dependent, site specific, but primarily positive. However, L. monocytogenes was inversely related with indicator bacteria densities. Campylobacter, Salmonella, Giardia cysts and Cryptosporidium oocysts were most frequently detected in the fall. E. coli O157:H7 was detected at a very low frequency. Exploratory decision tree analyses found overall that E. coli densities were the most utilitarian classifiers of parasite/pathogen presence and absence, followed closely by fecal coliforms, and to a lesser extent enterococci and total coliforms. Indicator bacteria densities that classified pathogen presence and absence groupings, were all below 100 CFU per 100 mL(-1). Microorganism relationships with rainfall indices and tributary discharge variables were globally weak to modest, and generally inconsistent among season, site and microorganism. But, overall rainfall and discharge were primarily positively associated with indicator bacteria densities and pathogen detection. Instances where a pathogen was detected in the absence of a detectable bacterial indicator were extremely infrequent; thus, the fecal indicators were conservative surrogates for a variety of pathogenic microorganisms in this agricultural setting. The results from this study indicate that no one indicator or simple hydrological index is entirely suitable for all environmental systems and pathogens/parasites, even within a common geographic setting. These results place more firmly into context that robust prediction and/or indicator utility will require a more firm understanding of microorganism distribution in the landscape, the nature of host sources, and transport/environmental fate affinities among pathogens and indicators.
加拿大安大略省东部的南民族河流域以混合农业为特色。2004年至2006年期间，每两周从该流域内不同河流等级的河流支流上多达24个离散采样点采集了1600多个水样。对水样进行了以下分析：指示菌（大肠杆菌、产气荚膜梭菌、肠球菌、总大肠菌群和粪大肠菌群）的密度、病原菌（单核细胞增生李斯特菌、大肠杆菌O157:H7、沙门氏菌属、弯曲杆菌属）的存在情况，以及寄生虫贾第虫囊肿和隐孢子虫卵囊的密度。指示菌、病原菌与寄生虫卵囊/囊肿之间的关系总体较弱，具有季节性、地点特异性，但主要呈正相关。然而，单核细胞增生李斯特菌与指示菌密度呈负相关。弯曲杆菌、沙门氏菌、贾第虫囊肿和隐孢子虫卵囊在秋季最常被检测到。大肠杆菌O157:H7的检测频率非常低。探索性决策树分析总体发现，大肠杆菌密度是寄生虫/病原菌存在与否的最实用分类指标，其次是粪大肠菌群，肠球菌和总大肠菌群的程度较低。对病原菌存在与否进行分类的指示菌密度均低于每100 mL（-1）100 CFU。微生物与降雨指数和支流流量变量之间的关系总体较弱至中等，并且在季节、地点和微生物之间通常不一致。但是，总体降雨量和流量主要与指示菌密度和病原菌检测呈正相关。在没有可检测到的细菌指示物的情况下检测到病原菌的情况极为罕见；因此，在这种农业环境中，粪便指示物是多种病原微生物的保守替代物。这项研究的结果表明，即使在共同的地理环境中，也没有一种单一的指标或简单的水文指数完全适用于所有环境系统和病原菌/寄生虫。这些结果更有力地表明，可靠的预测和/或指标效用将需要更深入地了解景观中的微生物分布、宿主来源的性质以及病原菌和指示物之间的传播/环境归宿亲和力。
