Introduction and objective:
Legionella spp. are ubiquitous worldwide in natural water sources (rivers, lakes) as well as in man-made water systems (cooling towers, tap water, spas). The most common species causing the disease in humans is Legionella pneumophila. Pathogenicity of Legionella is related to the genes associated with virulence. The study aimed to detect Legionella spp. DNA in man-made water systems, and to examine the presence of selected virulence genes (lvh, rtxA, enhC) in Legionella-positive samples.

Material and methods:
A total of 52 water samples from hot and cold water systems collected from urban and rural areas were investigated for the presence of Legionella by polymerase chain reaction (PCR). The detection of three virulence loci (lvh, rtxA, and enhC) in water samples was investigated using PCR.

Legionella spp. was detected in over half the tested samples (55.77%), both in water from hot (55.88%) and cold (55.56%) water systems. Sequencing confirmed the presence of Legionella pneumophila in the tested samples. Among all Legionella-positive isolates, at least one virulence gene was detected in the case of 55.17% (16/29) of environmental samples. The lvh locus was most frequently present in all specimens.

The presence of Legionella pneumophila, the causative agent of Legionnaires’ disease, in hot and cold water systems from rural and urban localities, indicates a risk to public health. The occurrence of virulence genes in tested samples suggests that L. pneumophila has the potential to cause human disease.

The study was funded by Institute of Rural Health in Lublin within a subsidy from the Ministry of Science and Higher Education in Warsaw, Poland (Project No. 15001).
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