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

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

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1260460

DOI=10.3389/fmicb.2023.1260460

ISSN=1664-302X

ABSTRACT=<p>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: <italic>Legionella pneumophila</italic>, nontuberculous mycobacterial species (e.g., <italic>Mycobacterium avium</italic>, <italic>M. intracellulare</italic>, and <italic>M. abscessus</italic>), and <italic>Pseudomonas aeruginosa</italic> along with two groups of amoebas (<italic>Acanthamoeba</italic> and <italic>Vermamoeba vermiformis</italic>). 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. <italic>L. pneumophila</italic> was the most prevalent pathogen (86% of samples), followed by <italic>M. intracellulare</italic> (66%) and <italic>P. aeruginosa</italic> (21%). Interestingly, <italic>M. avium</italic> and <italic>M. abscessus</italic> were not detected in any samples. The data revealed a relatively low prevalence of <italic>Acanthamoeba</italic> spp. (4%), while <italic>V. vermiformis</italic> was widely detected (81%) across all the sampling locations within the HPS. Locations with a high concentration of <italic>L. pneumophila</italic> and <italic>M. intracellulare</italic> coincided with the highest detection of <italic>V. vermiformis</italic>, 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.</p>