Presence and Persistence of Legionella spp. in Groundwater

Abstract

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.

Multiplication of Legionella pneumophila Sequence Types 1, 47, and 62 in Buffered Yeast Extract Broth and Biofilms Exposed to Flowing Tap Water at Temperatures of 38°C to 42°C

“…38°C, whereas L. pneumophila predominated in water from a source at ca. 45°C (50). Elevated L. pneumophila colony counts were also observed in residential hot water systems at a water temperature ranging from 35 to 45°C (51).…”

High Diversity and Abundance of Legionella spp. in a Pristine River and Impact of Seasonal and Anthropogenic Effects

“…This could suggest that the Legionella spp. originate from the source of the river or that they could come from groundwater and/or atmospheric inputs, as has been proposed previously (14,37). Very few studies have quantified Legionella abundance in their natural reservoirs, and the majority of these used culturing methods.…”

“…The major reservoirs of Legionella spp. are freshwater environments such as lakes, rivers, groundwater, and hot springs, but they can also survive in seawater and water from wastewater treatment plants (WWTPs) (12,14,22,34,38). Their presence in these different reservoirs demonstrates their ability to grow, or at least persist, under a wide range of different environmental conditions (e.g., temperature, pH).…”

Legionella oakridgensis ATCC 33761 genome sequence and phenotypic characterization reveals its replication capacity in amoebae

“…oakridgensis was first reported in 1983 after isolation from industrial cooling towers, however, meanwhile L. oakridgensis was also found in ground water or compost facilities (Orrison et al, 1983, Costa et al, 2005Casati et al, 2010). L. oakridgensis, unlike all other Legionella species, does not require additional L-cysteine for growth in media or on agar plates (Orrison et al, 1983).…”