Research Group for Plant Health and Food Safety, Department of Plant and Soil Sciences, University of Pretoria, Room: 2-18, Hatfield Campus, Agriculture Building, Private Bag X20, Hatfield/Pretoria, South Africa.
Environ Monit Assess. 2018 Feb 27;190(3):177. doi: 10.1007/s10661-018-6554-1.
A total of 285 water samples were collected from 71 roof harvested rainwater tanks from four villages in different provinces over a two-year (2013-2014) period during the early (October to December) and late (January to March) rainy season. Water quality was evaluated based on Escherichia coli, faecal coliforms and Enterococcus spp. prevalence using the IDEXX Quanti-Tray quantification system. Real-Time PCR was used to analyse a subset of 168 samples for the presence of Shigella spp., Salmonella spp. and E. coli virulence genes (stx1, stx2 and eaeA). Escherichia coli were detected in 44.1% of the samples, Enterococcus spp. in 57.9% and faecal coliforms in 95.7%. The most prevalent E. coli concentrations in harvested rainwater were observed in 29.1% of samples and 22.5% for Enterococcus spp. and, were within 1-10 cfu/100 ml and 10-100 cfu/100 ml, respectively, whereas those for faecal coliforms (36.6%) were within 100-1000 cfu/100 ml. On average 16.8% of the samples had neither E. coli nor Enterococcus spp. detected, while 33.9% had only Enterococcus spp. and 23.7% had only E. coli. E. coli and Enterococcus spp. were detected together in 25.5% of the samples. Evaluation of samples for potential pathogenic bacteria showed all tested samples to be negative for the Shigella spp. ipaH gene, while five tested positive for Salmonella ipaB gene. None of the samples tested positive for the stx1 and stx2 genes, and only two tested positive for the eaeA gene. These findings are potentially useful in the development of a simplified risk assessment strategy based on the concentrations of indicator bacteria.
在为期两年的时间里（2013-2014 年），从四个省份的四个村庄的 71 个屋顶雨水收集池中收集了总共 285 个水样。使用 IDEXX Quanti-Tray 定量系统，基于大肠杆菌、粪大肠菌群和肠球菌属的流行情况评估水质。使用实时 PCR 分析了 168 个样本中的一部分，以检测志贺氏菌属、沙门氏菌属和大肠杆菌的毒力基因（stx1、stx2 和 eaeA）。在 44.1%的样本中检测到大肠杆菌，在 57.9%的样本中检测到肠球菌属，在 95.7%的样本中检测到粪大肠菌群。在采集的雨水样本中，大肠杆菌的浓度最常见于 29.1%的样本，肠球菌属的浓度最常见于 22.5%，分别为 1-10cfu/100ml 和 10-100cfu/100ml，而粪大肠菌群的浓度（36.6%）为 100-1000cfu/100ml。平均而言，16.8%的样本既未检测到大肠杆菌也未检测到肠球菌属，而 33.9%的样本仅检测到肠球菌属，23.7%的样本仅检测到大肠杆菌属。在 25.5%的样本中同时检测到大肠杆菌属和肠球菌属。对潜在致病菌样本的评估显示，所有测试样本均未检测到志贺氏菌属的 ipaH 基因，但有五个样本对沙门氏菌属的 ipaB 基因呈阳性。没有样本对 stx1 和 stx2 基因呈阳性，只有两个样本对 eaeA 基因呈阳性。这些发现可能有助于根据指示菌的浓度制定简化的风险评估策略。
