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

Vicente Gomez-Alvarez; Hodon Ryu; Min Tang; Morgan McNeely; Christy Muhlen; Megan Urbanic; Daniel Williams; Darren Lytle; Laura Boczek

doi:10.3389/fmicb.2023.1260460

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

Front Microbiol. 2023 Oct 17:14:1260460. doi: 10.3389/fmicb.2023.1260460. eCollection 2023.

Authors

Vicente Gomez-Alvarez¹, Hodon Ryu¹, Min Tang², Morgan McNeely¹, Christy Muhlen¹, Megan Urbanic², Daniel Williams¹, Darren Lytle¹, Laura Boczek¹

Affiliations

¹ Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, United States.
² Oak Ridge for Science and Education Research Fellow at U.S. Environmental Protection Agency, Cincinnati, OH, United States.

Abstract

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 groups of 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 drinking 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.

Keywords: Legionella pneumophila; free-living amoeba; microbial communities; opportunistic pathogens; premise plumbing.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was supported by EPA Office of Research and Development’s Safe and Sustainable Water Resources Program (SSWR.7). This work was also supported in part by an appointment to the Internship/Research Participation Program at the Office of Research and Development, U.S. EPA, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and EPA.