Research Group on Quality, Safety and Bioactivity of Plant Foods, CEBAS-CSIC, Campus Universitario de Espinardo, 25, 30100, Murcia, Spain.
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NW, USA.
Water Res. 2018 Jan 1;128:226-233. doi: 10.1016/j.watres.2017.10.041. Epub 2017 Oct 23.
To establish the association between microbial indicators and the presence of foodborne pathogens in irrigation water, Escherichia coli was enumerated using two quantification methods (plate counts and PMA-qPCR) and presence/absence of pathogenic microorganisms, including five strains from the Shiga toxigenic E. coli (O157:H7, O26, O103, O111 and O145) and Salmonella spp. were evaluated. The results confirmed that surface water can be considered a microbial hazard when used for irrigation. The levels of viable E. coli were very similar to those of cultivable E. coli, except for irrigation water obtained from water reservoirs. Comparison between the E. coli counts in samples positive and negative for the presence of pathogenic bacteria for the evaluated water sources identified E. coli level of 2.35 log cfu/100 mL as a cut-off able to correctly predict positive and negative samples with 93% sensitivity and 66% specificity, respectively. Thus, for the samples with levels of E. coli under 2.35 log cfu/100 mL (e.g., 2.24 log cfu/100 mL) there was a 90% probability that the samples were not contaminated with pathogenic microorganism in locations with similar prevalence. E. coli levels in irrigation water were affected by the ambient temperature confirming that water source and climate conditions should be taken into account by growers when designing a sampling program and the frequency of the monitoring to make a better and more efficient use of their resources.
为了建立微生物指标与灌溉水中食源性致病菌存在之间的关系，使用两种定量方法（平板计数和 PMA-qPCR）对大肠杆菌进行了计数，并评估了致病性微生物的存在/不存在，包括来自产志贺毒素大肠杆菌（O157:H7、O26、O103、O111 和 O145）和沙门氏菌属的五种菌株。结果证实，地表水在用于灌溉时可被视为微生物危害。除了从水库获得的灌溉水外，可培养大肠杆菌的水平与可培养大肠杆菌的水平非常相似。比较评估水源中致病性细菌存在的阳性和阴性样本中的大肠杆菌计数，确定 2.35 log cfu/100 mL 作为可正确预测阳性和阴性样本的截止值，分别具有 93%的灵敏度和 66%的特异性。因此，对于大肠杆菌水平低于 2.35 log cfu/100 mL（例如 2.24 log cfu/100 mL）的样本，在类似流行率的地点，样本没有被致病性微生物污染的概率为 90%。灌溉水中的大肠杆菌水平受到环境温度的影响，这证实了水源和气候条件应被种植者在设计采样计划和监测频率时考虑在内，以便更好、更有效地利用他们的资源。
