Citation:

Buse, Helen Y., B. Morris, V. Gomez-Alvarez, Jeff Szabo, AND J. Hall. Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System. PATHOGENS. MDPI, Basel, Switzerland, 9(7):567, (2020). https://doi.org/10.3390/pathogens9070567

Impact/Purpose:

Current approaches to Legionella exposure prevention, e.g. through environmental monitoring and/or implementation of building water management plans, requires a thorough understanding of their persistence and transmission mechanisms in premise plumbing systems. In this study, to better understand BWS conditions supporting Legionella survival, microbial water quality parameters, such as the occurrence of Legionella spp., L. pneumophila, and Mycobacterium intracellulare; and the free-living amoebae hosts, Acanthamoeba spp. and Vermamoeba vermiformis, and heterotrophic plate count levels, were monitored, along with chemical water quality, engineering, and operational parameters. Determining how various physical, chemical, and microbial BWS characteristics influence Legionella survival may elucidate ways to minimize and eliminate their growth within these systems.

Description:

Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18-28 months at six locations differing in plumbing material and potable water age, quality, and usage. A total of 114 bulk water and 57 biofilm samples were analyzed. Legionella culturability fluctuated seasonally with most culture positive samples being collected during the winter compared to the spring, summer, and fall months. Positive and negative correlations between Legionella and L. pneumophila occurrence and other physio-chemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 Legionella isolates, from four locations across three timepoints, identified seven isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; two as L. pneumophila sg5 ST1950 and ST2037; and six as L. feeleii sg1/2. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence detected at four and two locations, respectively, throughout the study. Collectively, this information will aid in the design of effective preventative measures and system operations to control risks associated with Legionella drinking water exposure.

URLs/Downloads:

Record Details: