Abstract：
Seven public water systems in Minnesota, USA were analyzed from one to five times over a two-year period to assess temporal changes in the concentrations of total bacteria, Legionella spp., and Legionella pneumophila from source (i.e., raw water) through the water treatment process to the end water user. Bacterial biomass was collected by filtering large volumes of raw water (12 to 425 L, median: 38 L) or finished and tap water (27 to 1205 L, median: 448 L) using ultrafiltration membrane modules. Quantitative PCR (qPCR) was then used to enumerate all bacteria (16S rRNA gene fragments), all Legionella spp. (ssrA), and Legionella pneumophila (mip). Total coliforms, Escherichia coli, and L. pneumophila also were quantified in the water samples via cultivation. Median concentrations of total bacteria and Legionella spp. (ssrA) in raw water (8.5 and 4.3 log copies/L, respectively) decreased by about 2 log units during water treatment. The concentration of Legionella spp. (ssrA) in water collected from distribution systems inversely correlated with the total chlorine concentration for chloraminated systems significantly (p = 0.03). Although only 8 samples were collected from drinking water distribution systems using free chlorine as a residual disinfectant, these samples had significantly lower concentrations of Legionella spp. (ssrA) than samples collected from the chloraminated systems (p = 5 × 10-4). There was considerable incongruity between the results obtained via cultivation-independent (qPCR) and cultivation-dependent assays. Numerous samples were positive for L. pneumophila via cultivation, none of which tested positive for L. pneumophilia (mip) via qPCR. Conversely, a single sample tested positive for L. pneumophilia (mip) via qPCR, but this sample tested negative for L. pneumophilia via cultivation. Overall, the results suggest that conventional treatment is effective at reducing, but not eliminating, Legionella spp. from surface water supplies and that residual disinfection is effective at suppressing these organisms within drinking water distribution systems.
摘要：
明尼苏达州的七个公共供水系统，美国在两年的时间内进行了一到五次分析，以评估总细菌浓度的时间变化，军团菌属。,和来自来源的嗜肺军团菌(即，原水)通过水处理过程提供给最终用水者。通过过滤大量原水（12至425L，中位数：38升）或成品和自来水（27至1205升，中位数：448L）使用超滤膜组件。然后使用定量PCR（qPCR）计数所有细菌（16SrRNA基因片段），所有军团菌属。(ssrA),和嗜肺军团菌（mip）。大肠杆菌总数,大肠杆菌,和嗜肺乳杆菌也通过培养在水样中定量。细菌总数和军团菌的中位数浓度。（ssrA）在原水中（8.5和4.3日志拷贝/L，分别)在水处理期间减少了约2个对数单位。军团菌的浓度。从分配系统收集的水中的（ssrA）与氯化系统的总氯浓度成反比（p=0.03）。尽管仅从饮用水分配系统中收集了8个使用游离氯作为残留消毒剂的样品，这些样品明显低于从氯化系统收集的样品（p=5×10-4）。通过培养非依赖性(qPCR)和培养依赖性测定获得的结果之间存在相当大的不一致。通过培养，许多样品对嗜肺乳杆菌呈阳性，没有一个通过qPCR检测出肺炎支原体（mip）呈阳性。相反，单个样本通过qPCR检测为肺炎支原体（mip）阳性，但是这个样本通过培养检测出肺炎杆菌呈阴性。总的来说,结果表明，常规治疗可有效减少，但不能消除，军团菌属。来自地表水供应，并且残留的消毒有效地抑制了饮用水分配系统中的这些生物。
