Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System

Abstract

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 physiochemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 presumptive Legionella isolates, from four locations across three time points, identified nine isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; three as L. pneumophila sg5 ST1950 and ST2037; six as L. feeleii; and one as Ochrobactrum. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence at four and two locations, respectively. Viewed collectively with similar studies, this information will enable a better understanding of the engineering, operational, and water quality parameters supporting Legionella growth within BWSs.

Characterization of Legionella pneumophila Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank

“…Many studies have demonstrated that the main sources for LD are the drinking water distribution systems (DWDS) in large buildings like hospitals and hotels [11][12][13]. The contamination of hospital water systems with Legionella is considered to pose a high risk for patients, especially for those with severe diseases.…”

Editorial Comments to the Special Issue: “Legionella Contamination in Water Environment”

“…Moreover, the study of Martin and co-workers [16] demonstrated, under controlled laboratory conditions, the importance of considering interactive effects with flow and pipe materials, particularly with respect to relative water corrosivity and influence on residual chlorine levels, in keeping Legionella levels low. The complex interaction between the various chemical, physical, and microbiological parameters and Legionella contamination is also highlighted by Buse et al [10]. In their study, negative and positive correlations between Legionella and some water characteristics (pH, temperature, turbidity, chlorine, Heterotrophic plate count, and Vermamoeba vermiformis contamination) were observed and they varied between location and sample types.…”

“…This method provides a good basis for detailed studies of the health and water management relevant traits of L. pneumophila in support of a better clinical and DWDS management. The Whole Genome Sequencing (WGS) also provides detailed genetic information about the Legionella strain in large building water system, beyond that obtained from SBT alone, enabling potential subspecies identification, refined taxonomic classification, and genetic profiling for virulence properties [10].…”

Occurrence of Legionella spp. in Man-Made Water Sources: Isolates Distribution and Phylogenetic Characterization in the Emilia-Romagna Region

“…In the H environment, the mip -gene tree showed eight clades that were highly conserved, with exceptions in two species— Lp , where five subclades relating to the different strains were identified, and one clade represented by L. feeleii with 98.2% similarity to the ATCC 35072 reference strains, which could represent a misidentification. It is clear that this difference requires more research by studying more genes, as demonstrated in several studies [ 52 , 53 , 54 , 55 ]. Similarly, in the C population, it is possible to find seven clades, with two subclades in Lp (two different strains of Corby and Paris) and three in L. feeleii, with a percentage of similarity from 99.4% to 98.4%.…”