Water heater temperature set point and water use patterns influence Legionella pneumophila and associated microorganisms at the tap
Water heater temperature set point and water use patterns influence Legionella pneumophila and associated microorganisms at the tap
复制标题
热水器温度设定点和用水模式影响水龙头处的嗜肺军团菌和相关微生物
作者：
W. Rhoads;Pan Ji;A. Pruden;M. Edwards
降低热水器的设定点和减少使用饮用水是节约用水和能源的常用方法；然而，在过去的文献中，关于热水器温度和用水方式对机会性病原体，特别是嗜肺军团菌发生的影响存在差异。我们的目标是进行一项受控的、可重复的中试规模调查，以解决这一知识差距，使用连续再循环热水器检查三种用水条件下的五个热水器设定点（39-58°C）。我们假设水龙头处嗜肺乳杆菌的水平取决于热水器温度、水流频率和居民管道生态的共同影响。我们证实温度设置是抑制嗜肺乳杆菌生长的关键因素，无论是在连续再循环热水管道和远端水龙头。例如，在51°C时，与39°C相比，循环管道中的浮游嗜肺乳杆菌减少了28.7倍，并阻止了生物膜的重新定植。然而，嗜肺乳杆菌仍然持续到58°C，有证据表明它在本研究的条件下生长。此外，在低使用率的水龙头中暴露在51°C的水中似乎是嗜肺乳杆菌的最佳选择（例如，其数量是高使用率水龙头的125倍）。我们随后探索了嗜肺乳杆菌和其他生态相关微生物之间的关系，注意到升高的温度在细菌总数方面没有一般的消毒效果。我们记录了嗜肺乳杆菌和军团菌之间的关系，并注意到与蠕形虫相关的几个实例，并且通常发现在温度和水使用频率的范围内与这种变形虫宿主存在动态关系。我们的研究为了解饮用水热水系统的微生物生态提供了一个新的窗口，并有助于解决过去关于水温和停滞对嗜肺乳杆菌影响的文献差异，这是越来越多的爆发的原因。考虑到社会向“绿色”建筑的发展，以及协调建筑设计创新与公共卫生的需要，这项工作尤其及时。
Lowering water heater temperature set points and using less drinking water are common approaches to conserving water and energy; yet, there are discrepancies in past literature regarding the effects of water heater temperature and water use patterns on the occurrence of opportunistic pathogens, in particular Legionella pneumophila. Our objective was to conduct a controlled, replicated pilot-scale investigation to address this knowledge gap using continuously recirculating water heaters to examine five water heater set points (39–58 °C) under three water use conditions. We hypothesized that L. pneumophila levels at the tap depend on the collective influence of water heater temperature, flow frequency, and the resident plumbing ecology. We confirmed temperature setting to be a critical factor in suppressing L. pneumophila growth both in continuously recirculating hot water lines and at distal taps. For example, at 51 °C, planktonic L. pneumophila in recirculating lines was reduced by a factor of 28.7 compared to 39 °C and was prevented from re-colonizing biofilm. However, L. pneumophila still persisted up to 58 °C, with evidence that it was growing under the conditions of this study. Further, exposure to 51 °C water in a low-use tap appeared to optimally select for L. pneumophila (e.g., 125 times greater numbers than in high-use taps). We subsequently explored relationships among L. pneumophila and other ecologically relevant microbes, noting that elevated temperature did not have a general disinfecting effect in terms of total bacterial numbers. We documented the relationship between L. pneumophila and Legionella spp., and noted several instances of correlations with Vermamoeba vermiformis, and generally found that there is a dynamic relationship with this amoeba host over the range of temperatures and water use frequencies examined. Our study provides a new window of understanding into the microbial ecology of potable hot water systems and helps to resolve past discrepancies in the literature regarding the influence of water temperature and stagnation on L. pneumophila, which is the cause of a growing number of outbreaks. This work is especially timely, given society’s movement towards “green” buildings and the need to reconcile innovations in building design with public health.