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

Abstract

The diversity and dynamics of Legionella species along a French river watershed subject to different thermal and wastewater discharges during an annual cycle were assessed by 16S rRNA gene sequencing and by a fingerprint technique, single-strand conformation polymorphism. A high diversity of Legionella spp. was observed at all the sampling sites, and the dominant Legionella clusters identified were most closely related to uncultured bacteria. The monthly monitoring revealed that Legionella sp. diversity changes were linked only to season at the wastewater site whereas there was some evidence for anthropogenic effects on Legionella sp. diversity downstream of the thermal bath. Quantification of Legionella pneumophila and Legionella spp. by culture and quantitative PCR (qPCR) was performed. Whereas only L. pneumophila was quantified on culture media, the qPCR assay revealed that Legionella spp. were ubiquitous and abundant from the pristine source of the river to the downstream sampling sites. These results suggest that Legionella spp. may be present at significant concentrations in many more freshwater environments than previously thought, highlighting the need for further ecological studies and culturing efforts.

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

“…in water systems. A large diversity of Legionella spp., many of which are as yet uncultured, is ubiquitous in freshwater environments at temperatures of Ͻ20°C (36,42,43,44,45,46). L. pneumophila is not cultured or only sporadically cultured from these low-temperature environments.…”

Molecular Survey of the Occurrence of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa, and Amoeba Hosts in Two Chloraminated Drinking Water Distribution Systems

“…It is not clear whether the season contributes to the pattern similarity, since sampling at both locations occurred during warm seasons (spring and fall). A seasonal effect on Legionella diversity or distribution has been found in one location of a French pristine river (60) and in cooling towers (74). It is possible that seasonal factors could have been at play in the present study by influencing the bacterial growth environment (e.g., temperature, humidity, and water chemistry) and operation of premise plumbing (e.g., water heater usage).…”

Microbiological and Clinical Studies of Legionellosis in 33 Patients with Cancer

“…In the environment, however, Legionella species are diverse, as revealed in a French study (29). Another large-scale French study compared clinical and environmental Legionella isolates and noted that L. pneumophila serogroup 1 accounted for 28% of the environmental isolates, compared to 95% of the clinical isolates (30).…”