Abstract
Growth of Legionella pneumophila and other opportunistic pathogens (OPs) in drinking water premise plumbing poses an increasing public health concern. Premise plumbing is constructed of a variety of materials, creating complex environments that vary chemically, microbiologically, spatially, and temporally in a manner likely to influence survival and growth of OPs. Here we systematically review the literature to critically examine the varied effects of common metallic (copper, iron) and plastic (PVC, cross-linked polyethylene (PEX)) pipe materials on factors influencing OP growth in drinking water, including nutrient availability, disinfectant levels, and the composition of the broader microbiome. Plastic pipes can leach organic carbon, but demonstrate a lower disinfectant demand and fewer water chemistry interactions. Iron pipes may provide OPs with nutrients directly or indirectly, exhibiting a high disinfectant demand and potential to form scales with high surface areas suitable for biofilm colonization. While copper pipes are known for their antimicrobial properties, evidence of their efficacy for OP control is inconsistent. Under some circumstances, copper’s interactions with premise plumbing water chemistry and resident microbes can encourage growth of OPs. Plumbing design, configuration, and operation can be manipulated to control such interactions and health outcomes. Influences of pipe materials on OP physiology should also be considered, including the possibility of influencing virulence and antibiotic resistance. In conclusion, all known pipe materials have a potential to either stimulate or inhibit OP growth, depending on the circumstances. This review delineates some of these circumstances and informs future research and guidance towards effective deployment of pipe materials for control of OPs.
Highlights
Legionnaires’ Disease is the “leading cause of reportable waterborne illness” in the UnitedStates [1,2], with 52,000–70,000 cases per year [1,3,4], 8000–18,000 hospitalizations [5], an overall mortality rate of 15% [4], and high healthcare and legal costs [2,6,7,8]
Other opportunistic pathogens (OPs) such as nontuberculous mycobacteria (NTM), Pseudomonas aeruginosa, and Acanthamoebae, can be transmitted via tap water and tend to infect individuals belonging to certain risk groups [8]
Copper is sometimes present at trace levels in the source water or in distributed water mains, Copper is sometimes present at trace the source water or inthat distributed waterbeginning mains, but the main sources in premise plumbing are levels copperinpipes and brass fittings are installed but the main sources in premise plumbing are copper pipes and brass fittings that are installed at the service line connecting the building to the water main (Figure 2)
Summary
Legionnaires’ Disease is the “leading cause of reportable waterborne illness” in the United. Premise plumbing is characterized by high surface area to volume ratios, longer stagnation times, low disinfectant residual, areas with excess sediment and scale, chemically and biologically reactive plumbing materials, and water with relatively warm temperatures Such conditions can create ideal micro- and macro-environmental niches for growth of various OPs [1,8,23]. The selective pressures in premise plumbing might alter the physiologies of resident microbes in a manner that influences infectivity [38] All these phenomena are further complicated by the fact that premise plumbing configurations, hydraulics, temperature, and water use patterns including velocity, flow or stagnation events, all differ significantly from building to building. While there are many overarching similarities, every premise plumbing system is at least as variable as the occupants’ unique water use patterns and habits
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