Looking for the silver lining: Assessing the impact of silver in showerheads on opportunistic pathogen abundance and resistance

水消毒在预防微生物致病方面非常有效。然而，没有现有的策略可以完全防止通过饮用、淋浴和洗手接触水生微生物。虽然大多数微生物是无害的，甚至是有益的，但有些微生物是有害的。对于那些伤害病人或免疫系统较弱的人的机会性病原体尤其如此。机会性病原体每年导致成千上万的疾病，每年给国家带来巨大的医疗费用。镀银（Ag）水装置的设计就是为了解决这个问题。银的存在被认为可以杀死细菌，这是基于这种重金属已知的抗菌特性。然而，重金属暴露也会将一些细菌转化为耐抗生素的形式。抗生素耐药性被认为是美国最大的医疗保健挑战之一。这就提出了一个问题，即ag修正装置是否会产生比它们试图解决的问题更大的问题。这项研究旨在解决是否银修正创造条件，导致抗生素耐药性的形成。这将利用最先进的科学分子技术来探索嗜肺军团菌对ag修饰的莲蓬头的反应。军团菌被选为最重要的机会性病原体负责水传播死亡在美国。这项研究的成功完成将提供结果，可以指导进一步使用Ag修正夹具，以保护人类健康。对社会的好处包括推广和教育工作，这将提高国家的STEM能力和科学素养。经银（Ag）修饰的莲蓬头被认为可以通过银的抗菌特性减轻因水传播而引起的细菌感染。然而，它们在预防嗜肺军团菌、铜绿假单胞菌和非结核分枝杆菌等机会致病菌（OPs）引起的疾病方面的有效性证据存在严重局限性。例如，传统的基于培养的方法用于评估功效，而已知这些技术在OPs处于可存活但不可培养状态（VBNC）时提供假阴性结果。关于银的使用的第二个担忧是，新兴科学表明，由于接触银等重金属，细菌有可能产生抗生素耐药性。鉴于这些关切，迫切需要确定ag修正缓解方法是有利于还是进一步加剧人类健康结果。本研究的假设是，ag修饰的莲蓬头将以一种增加OP丰度和促进VBNC状态的方式影响室内管道中的微生物群落，从而增加对人类健康不利结果的可能性。这一假设将通过两个研究目标进行检验：(i)使用16S rRNA扩增子测序和数字液滴PCR对关键OPs进行绝对定量，确定淋浴喷头夹具设计的影响和Ag对淋浴喷头出水微生物群落的影响，以及（ii）进行有针对性的实验室实验，以分离水和/或淋浴喷头特性（ies），这些特性控制着嗜肺杆菌丰度及其在VBNC状态下存在的潜在机制。这些将使用一个定制的模拟真实淋浴环境的设备来实现，以阐明淋浴喷头和生物膜之间的关键相互作用，并揭示控制ag介导的失活或抗性发展的分子机制。这项研究的结果将为ag介导的缓解策略的有效性以及在淋浴水中诱导抗生素耐药性的可能性提供证据。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Water disinfection has been highly effective at preventing illness from microorganisms. However, no existing strategy can completely prevent waterborne microbial exposure through drinking, showering, and washing hands. While most microorganisms are harmless or even beneficial, some are harmful. This is particularly true for opportunistic pathogens that harm those who are sick or have weak immune systems. Opportunistic pathogens cause thousands of illnesses each year resulting in significant healthcare costs to the Nation each year. Silver (Ag) coated water fixtures have been designed to address this issue. The presence of Ag is thought to kill bacteria based on the known antimicrobial properties of this heavy metal. However, heavy metal exposure is also known to transform some bacteria into antibiotic resistant forms. Antibiotic resistance is considered one of the greatest healthcare challenges for the Nation. This raises the question of whether Ag-amended fixtures create an even larger problem than they are attempting to solve. This research is designed to resolve whether Ag amendment creates conditions that cause formation of antibiotic resistance. This will be achieved using state-of-the-science molecular techniques to explore the response of Legionella pneumophila to Ag-amended showerheads. Legionella is chosen as one of the most important opportunistic pathogens responsible for waterborne fatalities in the US. Successful completion of this research will provide results that can guide further use of Ag amended fixtures to protect human health. Benefits to society include outreach and education efforts that will enhance the STEM capability and scientific literacy of the Nation. Silver (Ag)-amended showerheads are thought to mitigate bacterial infection due to waterborne exposure through the antimicrobial properties of Ag. However, evidence of their efficacy in preventing illness due to opportunistic pathogens (OPs) like Legionella pneumophila, Pseudomonas aeruginosa, and nontuberculous mycobacteria has critical limitations. For example, conventional culture-based approaches are used to evaluate efficacy, while these techniques are known to provide false-negative results if OPs are in a viable but non-culturable state (VBNC). A second concern regarding the use of Ag is the emerging science demonstrating the potential for bacteria to develop antibiotic resistance due to exposure to heavy metals like Ag. Given these concerns, there is a critical need to determine whether Ag-amendment mitigation approaches benefit or further exacerbate human health outcomes. The hypothesis of this research is that Ag-modified showerheads will impact the microbial community in premise plumbing in a way that increases OP abundance and promotes the VBNC state, thus increasing the potential for adverse human health outcomes. This hypothesis will be tested through two research objectives to: (i) identify the impact of showerhead fixture design and influence of Ag on the microbial community in water exiting the showerheads using 16S rRNA amplicon sequencing and absolute quantification of key OPs using digital droplet PCR, and (ii) conduct targeted laboratory experiments to isolate the water and/or showerhead property(ies) governing the underlying mechanisms responsible for the abundance of L. pneumophila and their presence in the VBNC state. These will be achieved using a custom-built rig simulating a real shower environment to elucidate the critical interactions between the showerhead and the biofilm, and uncover the molecular mechanisms governing Ag-mediated inactivation or resistance development. The findings from this research will provide evidence for the efficacy of Ag-mediated mitigation strategies and the potential to induce antibiotic resistance in shower water.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.