Collins S, Stevenson D, Walker J, Bennett A
Biosafety Air and Water Microbiology Group, Public Health England, Porton Down, Salisbury, UK.
J Appl Microbiol. 2017 Jun;122(6):1692-1703. doi: 10.1111/jam.13461. Epub 2017 May 10.
To evaluate the usefulness of Legionella qPCR alongside traditional culture for enumeration of Legionella from water samples as part of both routine and public health investigation testing.
Routine water samples (n = 2002) and samples from public health investigations (n = 215) were analysed by culture and qPCR for Legionella spp., Legionella pneumophila and L. pneumophila sg-1. A negative qPCR result was highly predictive of a negative culture result for all water systems (negative predictive values, NPV from 97·4 to 100%). Positive predictive values (PPV) were lower (0-50%). Results for qPCR were generally larger than culture with average log differences of 1·1 for Legionella spp. and 1·2 for L. pneumophila. Alert and action levels of 1000 and 10 000 GU per litre, respectively, are proposed for Legionella qPCR for hot and cold water systems (HCWS). The use of qPCR significantly reduced the time to results for public health investigations by rapidly identifying potential sources and ruling out others, thus enabling a more rapid and efficient response.
The high NPV of qPCR supports its use to rapidly screen out negative samples without culture. Alert and action levels for Legionella qPCR for HCWS are proposed. Quantitative PCR will be a valuable tool for both routine and public health testing.
This study generated comparative data of >2000 water samples by qPCR and culture. Action and alert levels have been recommended that could enable duty holders to interpret qPCR results to facilitate timely Legionella control and public health protection.
评估军团菌定量聚合酶链反应（qPCR）与传统培养法在对水样中的军团菌进行计数方面的实用性，作为常规和公共卫生调查检测的一部分。
对常规水样（n = 2002）和公共卫生调查水样（n = 215）进行军团菌属、嗜肺军团菌及嗜肺军团菌1型的培养和qPCR分析。对于所有水系统，qPCR阴性结果对培养阴性结果具有高度预测性（阴性预测值，NPV为97·4%至1·00%）。阳性预测值（PPV）较低（0至50%）。qPCR结果通常大于培养结果，军团菌属的平均对数差异为1·1，嗜肺军团菌为1·2。建议将热水和冷水系统（HCWS）中军团菌qPCR的警戒水平和行动水平分别设定为每升1000和10000基因组单位（GU）。qPCR的使用通过快速识别潜在来源并排除其他来源，显著缩短了公共卫生调查的出结果时间，从而能够做出更快速有效的反应。
qPCR的高NPV支持其用于快速筛选出无需培养的阴性样本。提出了HCWS中军团菌qPCR的警戒水平和行动水平。定量PCR将成为常规和公共卫生检测的宝贵工具。
本研究通过qPCR和培养法生成了2000多个水样的比较数据。已推荐行动水平和警戒水平，这有助于责任方解读qPCR结果，以便及时控制军团菌并保护公众健康。
