Science Inventory

Assessing residential activity in a home plumbing system simulator: monitoring the occurrence and relationship of major opportunistic pathogens and phagocytic amoebas

Citation:

Gomez-Alvarez, V., H. Ryu, M. Tang, M. McNeely, C. Muhlen, M. Urbanic, D. Williams, D. Lytle, AND L. Boczek. Assessing residential activity in a home plumbing system simulator: monitoring the occurrence and relationship of major opportunistic pathogens and phagocytic amoebas. Frontiers in Microbiology. Frontiers, Lausanne, Switzerland, 14:1260460, (2023). https://doi.org/10.3389/fmicb.2023.1260460

Impact/Purpose:

Public health data shows that a significant fraction of the nation’s waterborne disease outbreaks (e.g. Legionnaires’ disease) in drinking water distribution system (DWDS) is attributable to premise plumbing (PP) systems. Very little information is available about the microbial occurrence within the water system of occupational buildings. It is important to understand the characteristics of these systems which amplify the potential public health risk relative to the DWDS. The water quality in PP is not monitored by U.S. EPA regulations except for the Lead and Copper Rule. The purpose of this research is to determine how and why these opportunistic waterborne pathogens can persist within PP systems and how to implement effective water management plans to mitigate exposure risks to PP pathogens.

Description:

Opportunistic premise plumbing pathogens (OPPPs) have been detected in buildings’ plumbing systems causing waterborne disease outbreaks in the United States. In this study, we monitored the occurrence of OPPPs along with free-living amoeba (FLA) and investigated the effects of residential activities in a simulated home plumbing system (HPS). Water samples were collected from various locations in the HPS and analyzed for three major OPPPs: Legionella pneumophila, nontuberculous mycobacterial species (e.g., Mycobacterium avium, M. intracellulare, and M. abscessus), and Pseudomonas aeruginosa along with two amoebas (Acanthamoeba and Vermamoeba vermiformis). A metagenomic approach was also used to further characterize the microbial communities. Results show that the microbial community is highly diverse with evidence of spatial and temporal structuring influenced by environmental conditions. L. pneumophila was the most prevalent pathogen (86% of samples), followed by M. intracellulare (66%) and P. aeruginosa (21%). Interestingly, M. avium and M. abscessus were not detected in any samples. The data revealed a relatively low prevalence of Acanthamoeba spp. (4%), while V. vermiformis was widely detected (81%) across all the sampling locations within the HPS. Locations with a high concentration of L. pneumophila and M. intracellulare coincided with the highest detection of V. vermiformis, suggesting the potential growth of both populations within FLA and additional protection in treated water. After a period of stagnation lasting at least 2-weeks, the concentrations of OPPPs and amoeba immediately increased and then decreased gradually back to the baseline. Furthermore, monitoring the microbial population after drainage of the hot water tank and partial drainage of the entire HPS demonstrated no significant mitigation of the selected OPPPs. This study demonstrates that these organisms can adjust to their environment during such events and may survive in biofilms and/or grow within FLA, protecting them from stressors in the supplied water.