Co-Occurrence of Free-Living Amoeba and Legionella in Drinking Water Supply Systems

Abstract

Background and Objectives: Legionella is one of the most important water-related pathogens. Inside the water supply systems and the biofilms, Legionella interact with other bacteria and free-living amoeba (FLA). Several amoebas may serve as hosts for bacteria in aquatic systems. This study aimed to investigate the co-occurrence of Legionella spp. and FLA in drinking water supply systems. Materials and Methods: A total of 268 water samples were collected from apartment buildings, hotels, and public buildings. Detection of Legionella spp. was performed in accordance with ISO 11731:2017 standard. Three different polymerase chain reaction (PCR) protocols were used to identify FLA. Results: Occurrence of Legionella varied from an average of 12.5% in cold water samples with the most frequent occurrence observed in hot water, in areas receiving untreated groundwater, where 54.0% of the samples were Legionella positive. The occurrence of FLA was significantly higher. On average, 77.2% of samples contained at least one genus of FLA and, depending on the type of sample, the occurrence of FLA could reach 95%. In the samples collected during the study, Legionella was always isolated along with FLA, no samples containing Legionella in the absence of FLA were observed. Conclusions: The data obtained in our study can help to focus on the extensive distribution, close interaction, and long-term persistence of Legionella and FLA. Lack of Legionella risk management plans and control procedures may promote further spread of Legionella in water supply systems. In addition, the high incidence of Legionella-related FLA suggests that traditional monitoring methods may not be sufficient for Legionella control.

Cooccurrence of Five Pathogenic Legionella spp. and Two Free-Living Amoebae Species in a Complete Drinking Water System and Cooling Towers

“…Previous reports have also shown that Acanthamoeba spp. and N. fowleri were detected in a drinking water supply system [43] and cooling towers by qPCR [45].…”

“…The cooccurrence of Legionella spp. and free-living amoebae has been examined solely in a drinking water supply system [43], a hospital water network [44], and cooling towers [45]. Each study focused mainly on the cooccurrence of L. pneumophila and various amoebae species by collecting a small volume (1 L or less) of the sample [43][44][45].…”

“…and free-living amoebae has been examined solely in a drinking water supply system [43], a hospital water network [44], and cooling towers [45]. Each study focused mainly on the cooccurrence of L. pneumophila and various amoebae species by collecting a small volume (1 L or less) of the sample [43][44][45]. It is hypothesized that sampling a small volume of water may not represent the true distribution of pathogenic amoebae and coexisting Legionella spp.…”

Causes, Factors, and Control Measures of Opportunistic Premise Plumbing Pathogens—A Critical Review

“…This relationship was first noted by Rowbotham [93] and has been described by Buse and Ashbolt [94] as a defining aspect of the Legionella lifecycle. To illustrate, Acanthamoeba (a genus of amoebae) are able to graze on Legionella at temperatures below 22 • C without repercussion; however, Legionella may bypass this process at higher temperatures to rapidly multiply, increase in virulence, and kill the amoebae host [95][96][97].…”

Water Age Effects on the Occurrence and Concentration of Legionella Species in the Distribution System, Premise Plumbing, and the Cooling Towers

“…Moreover, there is an estimation of 1.7 million people in Michigan that rely on municipal water supplies utilizing groundwater as their primary drinking water source [13]. In groundwater, Legionella has been found in several studies to range in concentrations from 10 1 to 10 4 CFU/100 mL [14][15][16][17]. Groundwater sources are notorious for having iron concentrations, and this may be considered problematic [18] as iron is a micronutrient for the growth of Legionella [19].…”