Abstract Potential health risks associated with water used to irrigate fresh produce are increasingly recognized worldwide, leading to the implementation of water quality standards as part of many food safety programs. These standards are generally based on the presence of the fecal indicator bacterium (FIB), generic Escherichia coli; however, the persistence and potential growth of this species in the environment suggests current standards may not accurately predict health risks associated with irrigation water. In this context, we evaluated enterococci as an alternate FIB for assessing agricultural water quality under baseflow conditions, which typically coincide with peak demands for supplemental irrigation in the study area. We compared culture-based concentrations of Enterococcus to E. coli over two growing seasons at four different irrigation canals in Alberta, Canada, that historically exceed the E. coli irrigation guideline on a frequent basis. We also examined enterococci species distributions among irrigation water, animal feces, and human sewage. Escherichia coli and enterococci were significantly correlated at three of the four canals, although on average, more guideline exceedances and higher mean concentrations of enterococci were reported. Specific differences in FIB dynamics were observed between canals. Most notably, enterococci concentrations were significantly higher than E. coli at one canal, while E. coli concentrations were significantly higher than enterococci at a different canal. Enterococci species distributions were markedly different between irrigation water and animal feces. Enterococci species reportedly associated with plants predominated in irrigation water, whereas these species were absent or present in very low proportions in human sewage and animal feces. Results of this study suggest the limitations of using enterococci for measuring microbial quality of irrigation water are similar to E. coli, in that risk analyses with respect to food safety may be confounded by the presence of environment-associated species and/or strains.

中文翻译：

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评估肠球菌作为灌溉水质的替代粪便指标

摘要 与用于灌溉新鲜农产品的水相关的潜在健康风险在世界范围内得到越来越多的认可，导致水质标准的实施作为许多食品安全计划的一部分。这些标准通常基于粪便指示菌 (FIB)、通用大肠杆菌的存在；然而，该物种在环境中的持久性和潜在增长表明，目前的标准可能无法准确预测与灌溉水相关的健康风险。在这种情况下，我们将肠球菌评估为在基流条件下评估农业水质的替代 FIB，这通常与研究区域补充灌溉的高峰需求相吻合。我们将基于培养的肠球菌浓度与大肠杆菌进行了比较。在加拿大艾伯塔省四个不同的灌溉渠道，两个生长季节的大肠杆菌，这在历史上经常超过大肠杆菌灌溉指南。我们还检查了灌溉水、动物粪便和人类污水中的肠球菌属物种分布。大肠杆菌和肠球菌在四个管道中的三个显着相关，尽管平均而言，报告了更多的指南超标和更高的肠球菌平均浓度。在根管之间观察到 FIB 动力学的特定差异。最值得注意的是，在一个管道中肠球菌的浓度显着高于大肠杆菌，而在另一根管道中，大肠杆菌的浓度显着高于肠球菌。灌溉水和动物粪便之间的肠球菌物种分布明显不同。据报道，肠球菌物种与灌溉水中占主导地位的植物有关，而这些物种在人类污水和动物粪便中不存在或存在的比例非常低。这项研究的结果表明，使用肠球菌测量灌溉水微生物质量的局限性与大肠杆菌相似，因为与环境相关的物种和/或菌株的存在可能会混淆与食品安全相关的风险分析。