Relationships between Free-Living Protozoa, Cultivable Legionella spp., and Water Quality Characteristics in Three Drinking Water Supplies in the Caribbean

Abstract

The study whose results are presented here aimed at identifying free-living protozoa (FLP) and conditions favoring the growth of these organisms and cultivable Legionella spp. in drinking water supplies in a tropical region. Treated and distributed water (؎30°C) of the water supplies of three Caribbean islands were sampled and investigated with molecular techniques, based on the 18S rRNA gene. The protozoan host Hartmannella vermiformis and cultivable Legionella pneumophila were observed in all three supplies. Operational taxonomic units (OTUs) with the highest similarity to the potential or candidate hosts Acanthamoeba spp., Echinamoeba exundans, E. thermarum, and an Neoparamoeba sp. were detected as well. In total, 59 OTUs of FLP were identified. The estimated protozoan richness did not differ significantly between the three supplies. In supply CA-1, the concentration of H. vermiformis correlated with the concentration of Legionella spp. and clones related to Amoebozoa predominated (82%) in the protozoan community. These observations, the low turbidity In tropical regions, the water temperature in drinking water distribution system is permanently about 30°C (4). In these regions, free-living protozoa (FLP), serving as hosts for pathogenic bacteria, including Acanthamoeba spp. (1, 38), Hartmannella spp. (37), and Naegleria spp. (38, 49), have been observed in surface water, wastewater, cooling towers, and drinking water (3,5,19,45). Certain FLP with pathogenic properties, viz. Acanthamoeba spp. (9, 21), Balamuthia mandrillaris (54), and Naegleria fowleri (59), can proliferate in drinking water-related biofilms at elevated temperatures (36). In addition, Legionella pneumophila, the main etiologic agent of Legionnaires' disease (12), which proliferates in freshwater at temperatures above 25°C (57), is frequently observed in these environments (14,31,39).FLP in aquatic environments feed on bacteria, fungi, other protozoa, and organic detritus in biofilms and sediments or in the planktonic phase (32). The abundance of prey organisms and detritus depends on the water composition and the hydraulic conditions in distribution systems, which therefore also affect both the FLP abundance and community composition (52, 55). Most information on community composition and abundance of FLP in freshwater environments has been obtained by using cultivation methods and microscopy. Recently, however, the presence and identities of such organisms in drinking water supplies in temperate regions have been studied by using molecular methods for detection and identification (33, 51). In two groundwater supplies in the Netherlands a total of 127 operational taxonomic units (OTUs) of FLP were identified based on their 18S rRNA gene sequences. FLP, mostly pathogens, have been characterized in only a few studies in tropical regions (3,5,19). In recent reviews it was concluded that more research is needed to determine which factors favor the growth of these organisms in water supplies (47,48).Cases of Legionnaires' disease have been reporte...

Multiple Legionella pneumophila Type II Secretion Substrates, Including a Novel Protein, Contribute to Differential Infection of the Amoebae Acanthamoeba castellanii, Hartmannella vermiformis, and Naegleria lovaniensis

“…Thus, we next sought to further improve our appreciation of T2S by incorporating a third amoebal host into our analysis. Although hartmannellae and acanthamoebae are the amoebae most frequently implicated as natural hosts for L. pneumophila, studies have implicated Naegleria species as being another natural reservoir (2,53,54). Therefore, we developed a model using N. lovaniensis.…”

Pyrosequencing analysis of eukaryotic and bacterial communities in faucet biofilms

“…Modeling of data from a biofilm-batch model indicated that amoebae can only multiply when a threshold concentration of prey bacteria is reached (Kuiper, 2006). Valster et al (2009Valster et al ( , 2011) indicated that the growth of H. vermiformis in drinking water distribution systems is limited at low biofilm concentrations or at ATP concentrations of ≤1 ng L −1 . A number of eukaryotic sequences from the WSW biofilm were related to those of species unlikely to live in biofilm systems, such as Arthropoda and Chordata in Metazoa, and Spermatophyta in Viridiplantae.…”

Nuclease Activity of Legionella pneumophila Cas2 Promotes Intracellular Infection of Amoebal Host Cells

“…Compatible with these data, the levels of cas2 mRNA are higher during intracellular growth than during growth in broth (15). The significance of these findings is heightened by the fact that acanthamoebae and hartmannellae are the most common amoebae in waters linked to Legionnaires' disease (6,7,16,17) and cas2 occurs in endemic strains linked to outbreaks (18).The Cas2 family of proteins is best known for being part of the bacterial and archeal clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein (Cas) system, a recently described system that confers immunity against phage and plasmid (19-21). Present in the genomes of nearly all archaea and the genomes of approximately one-half of bacteria, the CRISPR-Cas locus consists of the CRISPR array, which is composed of a variable number of palindromic repeats separated by unique spacer sequences, and a set of cas genes which encodes a variable number of Cas proteins.…”