Objective:
The study was aimed at determining whether Legionella pneumophila bacteria can be found in thermal saline waters used in balneotherapy.

Methods:
Water samples were collected from three thermal saline baths, supplied by thermal saline waters (type Cl – Na). The total number of bacteria was determined in the direct microscopic count under a fluorescence microscope The numbers of bacteria belonging to different phylogenetic groups (Eubacteria, Legionella sp. and Legionella pneumophila) were determined with the use of a molecular FISH method.

Results:
The highest average total number of bacteria as well as the highest average number of Eubacteria in the entire research cycle was recorded in bath 1. Bacteria belonging to the Legionella genus along with Legionella pneumophila were identified in all water samples collected from each bath. Moreover, biofilm containing cells of L. pneumophilla was identified in the collected water samples.

Conclusions:
The number of bacteria in water increases with the bath’s age. The Legionella pneumophila can successfully develop not only in fresh water bodies but in thermal saline baths as well. Still, it is uncertain whether the commonly applied culture method, developed for freshwater bodies, is also suitable for thermal saline baths.