Occurrence of Legionella in groundwater: an ecological study

The estimation of the average value of total species richness (Chao1) in supply A (153) was clearly higher than that for supply B (58). In each supply, about 77% of the sequences showed <97% similarity to described species. Sequences related to L. pneumophila were only incidentally observed. The Legionella populations of the two supplies are divided into two distinct clusters based on distances in the phylogenetic tree as fractions of the branch length. Thus, a large variety of mostly yet-undescribed Legionella spp. proliferates in unchlorinated water supplies at temperatures below 18°C. The lowest concentration and greatest diversity were observed in the supply with the low NOM concentration.

Section: Discussionmentioning

confidence: 65%

Concentration and Diversity of Uncultured Legionella spp. in Two Unchlorinated Drinking Water Supplies with Different Concentrations of Natural Organic Matter

Wullings

Bakker²,

Kooij

2011

“…Legionellae have been sporadically detected in groundwater (29,30,37). The increasing use of groundwater as a resource for potable water implies the need for more comprehensive data on the occurrence and distribution of legionellae in this type of environment.…”

Section: Discussionmentioning

confidence: 99%

Presence and Persistence of Legionella spp. in Groundwater

Costa¹,

Tiago²,

Costa

et al. 2005

Groundwater samples (111) from six different boreholes located in two geographical areas were examined for the presence of legionellae over a 7-year period. The number of Legionella isolates detected was generally low. The colonization of the aquifers was not uniform, and the persistence of Legionella was independent of the hydraulic pumps and the plumbing system present in the borehole. A total of 374 isolates identified by fatty acid methyl ester analysis belonged to Legionella pneumophila, L. oakridgensis, L. sainthelensi, and L. londiniensis. In area 1, L. oakridgensis constituted the major population detected, exhibiting only one random amplified polymorphic DNA (RAPD)-PCR profile. L. sainthelensi strains were less frequently isolated and also displayed a single RAPD profile, while L. pneumophila was only sporadically detected. In contrast, L. pneumophila comprised the vast majority of the isolates in area 2 and exhibited six distinct RAPD patterns, indicating the presence of different genetic groups; three L. londiniensis RAPD types were also detected. Two of the L. pneumophila and one of the L. londiniensis RAPD types were persistent in this environment for at least 12 years. The genetic structure of L. pneumophila groundwater populations, inferred from rpoB and dotA gene sequences, was peculiar, since the majority of the isolates were allied in a discrete group different from the lineages containing most of the type and reference strains of the three subspecies of L. pneumophila. Furthermore, gene exchange events related to the dotA allele could be envisioned.

“…Multiple-barrier SW treatment in The Netherlands causes a 3-to 6-log-unit reduction of vegetative cells (E. coli) and spores (sulfite-reducing clostridia) (21). Hence, in the absence of growth, L. pneumophila is not likely to be detectable in treated SW. L. pneumophila has been detected by use of the culture method in water from GW wells in the United States (11,47) but was only rarely observed in GW samples (1%) in Germany RNA gene amplified using Legionella-specific primers LEG-225 and LEG-858. The subtree in panel B includes mostly LLAP-related 16S rRNA gene sequences, and that in panel C contains sequences mostly originating from SW and samples from treated SW.…”

Section: Detection Of Legionella In Aquatic Environmentsmentioning

confidence: 99%

Occurrence and Genetic Diversity of Uncultured Legionella spp. in Drinking Water Treated at Temperatures below 15°C

Wullings

Kooij

2006

103

Representatives of the genus Legionella were detected by use of a real-time PCR method in all water samples collected directly after treatment from 16 surface water (SW) supplies prior to postdisinfection and from 81 groundwater (GW) supplies. Legionella concentrations ranged from 1.1 ؋ 10 3 to 7.8 ؋ 10 5 cells liter ؊1 and were significantly higher in SW treated with multiple barriers at 4°C than in GW treated at 9 to 12°C with aeration and filtration but without chemical disinfection. No Legionellae (<50 CFU liter ؊1 ) were detected in treated water by the culture method. Legionella was also observed in untreated SW and in untreated aerobic and anaerobic GW. Filtration processes in SW and GW treatment had little effect or increased the Legionella concentration, but ozonation in SW treatment caused about 1-log-unit reduction. A phylogenetic analysis of 16S rRNA gene sequences of 202 clones, obtained from a selection of samples, showed a high similarity (>91%) with Legionella sequences in the GenBank database. A total of 40 (33%) of the 16S rRNA gene sequences obtained from treated water were identified as described Legionella species and types, including L. bozemanii, L. worsleiensis, Legionella-like amoebal pathogen types, L. quateirensis, L. waltersii, and L. pneumophila. 16S rRNA gene sequences with a similarity of below 97% from described species were positioned all over the phylogenetic tree of Legionella. Hence, a large diversity of yet-uncultured Legionellae are common members of the microbial communities in SW and GW treated at water temperatures of below 15°C.