NUS Environmental Research Institute, National University of Singapore, T-Lab Building, #02-01, 5A Engineering Drive 1 117411, Singapore.
Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-03,1 Engineering Drive 2 117576, Singapore.
Water Res. 2021 Dec 1;207:117748. doi: 10.1016/j.watres.2021.117748. Epub 2021 Oct 13.
Human specific microbial source tracking (MST) markers which are highly specific to human waste contamination offer the advantage of better association with human pathogens than traditional microbial indicators. However, the performance of these MST markers may vary across different geographical regions. The magnitude of MST markers also plays an important role in interpreting the health risks. This study aims to (i) validate the specificity and sensitivity of human markers for tropical urban catchments; (ii) identify the threshold concentrations of MST markers, i.e. human polyomaviruses (HPyVs), Bacteroides thetaiotaomicron (B. theta) and Methanobrevibacter smithii (M. smithii), that correspond to the acceptable gastrointestinal (GI) illness risks associated with swimming using the QMRA approach; and (iii) validate the threshold concentrations of MST markers using the surveillance data obtained from the tropical urban environment. Among the three MST markers, HPyVs showed the highest specificity (100%) to sewage samples, followed by M. smithii (97%) and B. theta (90%). All MST markers showed 100% sensitivity towards sewage contamination, with B. theta present in highest abundance in sewage, followed by HPyVs and M. smithii. This study demonstrates a risk-based framework to identify the threshold concentrations of MST markers associated with GI illness risks in environmental waters by considering two main influencing factors (i.e. decay and dilution factors). This study successfully validated the B. theta threshold concentration range (581 to 8073 GC/100 mL) with field data (370 to 6500 GC/100 mL) in estimating GI illness risks with an Enterococcus model. Field data showed that the MST markers at threshold concentrations were able to classify the safe level in more than 83% of the samples, according to GI illness risks from Enterococcus and adenovirus. The study also highlighted the lack of associations between MST markers and GI illness risks from norovirus. With comprehensive information on specificity, sensitivity and threshold concentrations of MST markers, increasing confidence can be placed on identifying human source contamination and evaluating the health risks posed in environmental waters in Singapore.
人类特异性微生物源追踪 (MST) 标志物对人类粪便污染具有高度特异性，与传统微生物指标相比，能更好地与人类病原体相关联。然而，这些 MST 标志物在不同地理区域的性能可能会有所不同。MST 标志物的幅度也在解释健康风险方面发挥着重要作用。本研究旨在：(i) 验证热带城市集水区人类标志物的特异性和敏感性；(ii) 使用定量微生物风险评估 (QMRA) 方法确定与游泳相关的可接受胃肠道 (GI) 疾病风险所对应的 MST 标志物（人多瘤病毒 (HPyV)、双歧杆菌 (B. theta) 和甲烷短杆菌 (M. smithii)）的阈值浓度；(iii) 使用从热带城市环境中获得的监测数据验证 MST 标志物的阈值浓度。在这三种 MST 标志物中，HPyV 对污水样本的特异性最高（100%），其次是 M. smithii（97%）和 B. theta（90%）。所有 MST 标志物对污水污染的敏感性均为 100%，其中 B. theta 在污水中的丰度最高，其次是 HPyV 和 M. smithii。本研究通过考虑两个主要影响因素（即衰减和稀释因素），展示了一种基于风险的框架，用于确定与环境水中 GI 疾病风险相关的 MST 标志物的阈值浓度。本研究成功地用野外数据（370 至 6500 GC/100mL）验证了 B. theta 阈值浓度范围（581 至 8073 GC/100mL），用于用肠球菌模型估计 GI 疾病风险。野外数据表明，在 GI 疾病风险方面，根据肠球菌和腺病毒的风险，MST 标志物在阈值浓度下能够将 83%以上的样本分类为安全水平。该研究还强调了 MST 标志物与诺如病毒引起的 GI 疾病风险之间缺乏关联。通过了解 MST 标志物的特异性、敏感性和阈值浓度的综合信息，可以提高对识别人类源污染和评估新加坡环境水中健康风险的信心。
