Department of Urban Engineering, Graduate School of Engineering, The University of Tokyo.
Research Center for Water Environment Technology, Graduate School of Engineering, The University of Tokyo.
Microbes Environ. 2022;37(1). doi: 10.1264/jsme2.ME21065.
In premise plumbing, microbial water quality may deteriorate under certain conditions, such as stagnation. Stagnation results in a loss of disinfectant residual, which may lead to the regrowth of microorganisms, including opportunistic pathogens. In the present study, microbial regrowth was investigated at eight faucets in a building over four seasons in one year. Water samples were obtained before and after 24 h of stagnation. In the first 100 mL after stagnation, total cell counts measured by flow cytometry increased 14- to 220-fold with a simultaneous decrease in free chlorine from 0.17-0.36 mg L to <0.02 mg L. After stagnation, total cell counts were not significantly different among seasons; however, the composition of the microbial community varied seasonally. The relative abundance of Pseudomonas spp. was dominant in winter, whereas Sphingomonas spp. were dominant in most faucets after stagnation in other seasons. Opportunistic pathogens, such as Legionella pneumophila, Mycobacterium avium, Pseudomonas aeruginosa, and Acanthamoeba spp., were below the quantification limit for real-time quantitative PCR in all samples. However, sequences related to other opportunistic pathogens, including L. feeleii, L. maceachernii, L. micdadei, M. paragordonae, M. gordonae, and M. haemophilum, were detected. These results indicate that health risks may increase after stagnation due to the regrowth of opportunistic pathogens.
在前提管道中，微生物水质可能会在某些条件下恶化，例如停滞。停滞会导致消毒剂残留损失，这可能导致微生物重新生长，包括机会性病原体。在本研究中，在一年中的四个季节中，在一栋建筑中的八个水龙头处调查了微生物的再生长。在停滞 24 小时前后获得了水样。在停滞后的前 100 mL 中，通过流式细胞术测量的总细胞计数增加了 14 到 220 倍，同时游离氯从 0.17-0.36 mg/L 降至 <0.02 mg/L。停滞后，各季节的总细胞计数无显着差异；然而，微生物群落的组成随季节而异。在冬季，假单胞菌属的相对丰度占主导地位，而在其他季节停滞后的大多数水龙头中，鞘氨醇单胞菌属占主导地位。军团菌属、鸟分枝杆菌、铜绿假单胞菌和棘阿米巴属等机会性病原体在所有样品中的实时定量 PCR 定量下限以下。然而，检测到与其他机会性病原体相关的序列，包括 L. feeleii、L. maceachernii、L. micdadei、M. paragordonae、M. gordonae 和 M. haemophilum。这些结果表明，由于机会性病原体的再生长，停滞后健康风险可能会增加。
