Department of Agriculture, Food and Resource Sciences, University of Maryland Eastern Shore, Princess Anne, Maryland, USA.
Department of Biological Sciences, Delaware State University, Dover, Delaware, USA.
Microbiol Spectr. 2024 Apr 2;12(4):e0353623. doi: 10.1128/spectrum.03536-23. Epub 2024 Feb 20.
Alternative irrigation waters (rivers, ponds, and reclaimed water) can harbor bacterial foodborne pathogens like and , potentially contaminating fruit and vegetable commodities. Detecting foodborne pathogens using qPCR-based methods may accelerate testing methods and procedures compared to culture-based methods. This study compared detection by qPCR (real-time PCR) and culture methods in irrigation waters to determine the influence of water type (river, pond, and reclaimed water), season (winter, spring, summer, and fall), or volume (0.1, 1, and 10 L) on sensitivity, accuracy, specificity, and positive (PPV), and negative (NPV) predictive values of these methods. Water samples were collected by filtration through modified Moore swabs (MMS) over a 2-year period at 11 sites in the Mid-Atlantic U.S. on a bi-weekly or monthly schedule. For qPCR, bacterial DNA from culture-enriched samples ( = 1,990) was analyzed by multiplex qPCR specific for and . For culture detection, enriched samples were selectively enriched, isolated, and PCR confirmed. PPVs for qPCR detection of and were 68% and 67%, respectively. The NPV were 87% () and 85% (). Higher levels of qPCR/culture agreement were observed in spring and summer compared to fall and winter for ; for , lower levels of agreement were observed in winter compared to spring, summer, and fall. Reclaimed and pond water supported higher levels of qPCR/culture agreement compared to river water for both and , indicating that water type may influence the agreement of these results.
Detecting foodborne pathogens in irrigation water can inform interventions and management strategies to reduce risk of contamination and illness associated with fresh and fresh-cut fruits and vegetables. The use of non-culture methods like qPCR has the potential to accelerate the testing process. Results indicated that pond and reclaimed water showed higher levels of agreement between culture and qPCR methods than river water, perhaps due to specific physiochemical characteristics of the water. These findings also show that season and sample volume affect the agreement of qPCR and culture results. Overall, qPCR methods could be more confidently utilized to determine the absence of and in irrigation water samples examined in this study.
替代灌溉用水（河流、池塘和再生水）可能含有食源性致病菌，如 和 ，从而潜在污染水果和蔬菜商品。与基于培养的方法相比，使用基于 qPCR 的方法检测食源性致病菌可能会加速测试方法和程序。本研究比较了基于 qPCR（实时 PCR）和培养方法在灌溉水中检测 的情况，以确定水类型（河流、池塘和再生水）、季节（冬季、春季、夏季和秋季）或体积（0.1、1 和 10L）对这些方法的灵敏度、准确性、特异性和阳性（PPV）和阴性（NPV）预测值的影响。在两年期间，通过在马里兰州中部的 11 个地点，按照每两周或每月的时间表，使用改良的 Moore 拭子（MMS）通过过滤收集水样。对于 qPCR，通过多重 qPCR 分析从培养富集样品（=1990）中提取的细菌 DNA，该多重 qPCR 特异性针对 和 。对于培养检测，对富集样品进行选择性富集、分离和 PCR 确认。qPCR 检测 和 的 PPV 分别为 68%和 67%。NPV 分别为 87%（）和 85%（）。与秋季和冬季相比，春季和夏季的 qPCR/培养检测结果的一致性更高；对于 ，与春季、夏季和秋季相比，冬季的一致性较低。与河水相比，再生水和池塘水支持更高水平的 qPCR/培养一致性，这表明水类型可能会影响这些结果的一致性。
检测灌溉水中的食源性致病菌可以为干预和管理策略提供信息，以减少与新鲜和新鲜切割的水果和蔬菜相关的污染和疾病风险。使用非培养方法（如 qPCR）有可能加速测试过程。结果表明，与河水相比，池塘水和再生水的 qPCR 和培养方法之间的一致性更高，这可能是由于水的特定物理化学特性所致。这些发现还表明，季节和样品体积会影响 qPCR 和培养结果的一致性。总体而言，qPCR 方法可以更有信心地用于确定本研究中检查的灌溉水样中是否存在 和 。
