Dipartimento di Scienze dell'Ambiente e della Vita, Università degli Studi del Piemonte Orientale, "A. Avogadro", via T. Michel 11, 15121 Alessandria, Italy.
Environ Monit Assess. 2011 Jun;177(1-4):493-503. doi: 10.1007/s10661-010-1650-x. Epub 2010 Aug 17.
Escherichia coli O157:H7 and Salmonella are pathogenic microorganisms that can cause severe gastrointestinal illness in humans. These pathogens may be transmitted in a variety of ways, including food and water. The presence of Salmonella and E. coli O157:H7 in surface waters constitutes a potential threat to human health when used for either drinking or recreation. As with most waterborne pathogens, Salmonella and E. coli O157:H7 are difficult to detect and enumerate with accuracy in surface waters due to methodological limitations. The aim of this study was to develop a protocol for the detection of Salmonella spp., E. coli O157:H7 and E. coli virulence genes (stx (1), stx (2) and eae) in water using a single enrichment step and PCR. In spiked water samples, PCR results showed high sensitivity (<3 CFU/L) for both microorganisms. The protocol developed in this study has been applied in different surface waters in association with microbiological and physical analysis. The frequency of PCR positive samples was 33% for Salmonella and 2% for E. coli O157:H7 producing intimin (eae) and Shiga-like toxin I (stx (1)). Moreover, the finding of amplicons corresponding to eae and stx (1) genes in the absence of E. coli O157:H7 suggested the possible presence of other pathogenic bacteria that carry these genes (e.g. EHEC, Shigella strains). The results obtained showed that the developed protocol could be applied as a routine analysis of surface water for the evaluation of microbiological risks.
大肠杆菌 O157:H7 和沙门氏菌是能引起人类严重胃肠道疾病的病原微生物。这些病原体可能通过多种途径传播，包括食物和水。当用于饮用水或娱乐用水时，地表水存在沙门氏菌和大肠杆菌 O157:H7 对人类健康构成潜在威胁。与大多数水源性病原体一样，由于方法学上的限制，沙门氏菌和大肠杆菌 O157:H7 在地表水中难以准确检测和计数。本研究旨在开发一种使用单一富集步骤和 PCR 检测水中沙门氏菌、大肠杆菌 O157:H7 和大肠杆菌毒力基因 (stx(1)、stx(2)和 eae) 的方案。在加标水样中，PCR 结果显示两种微生物的灵敏度均很高（<3 CFU/L）。本研究中开发的方案已应用于不同的地表水，并与微生物学和物理分析相结合。沙门氏菌的 PCR 阳性样本频率为 33%，产肠细胞毒素（eae）和志贺样毒素 I（stx(1)）的大肠杆菌 O157:H7 为 2%。此外，在没有大肠杆菌 O157:H7 的情况下发现与 eae 和 stx(1)基因相对应的扩增子表明可能存在携带这些基因的其他致病性细菌（例如 EHEC、志贺氏菌株）。结果表明，所开发的方案可作为地表水微生物风险评估的常规分析方法。
