Genetic Diversity and Evaluation of Virulence Potential of Legionella pneumophila Isolated from Water-Supply Systems of Residential Buildings in Latvia

Abstract

Legionella is an opportunistic pathogen with a biphasic life cycle and humans are occasional hosts of Legionella. The aim of the study was to assess the distribution of virulence genes and genetic diversity among L. pneumophila isolated from water-supply systems of residential buildings in Latvia. In total, 492 water samples from 200 residential buildings were collected. Identification of Legionella spp. was performed according to ISO 11731 and 58 isolates were subjected to whole genome sequencing. At least one Legionella positive sample was found in 112 out of 200 apartment buildings (56.0%). The study revealed extensive sequence type diversity where 58 L. pneumophila isolates fell into 36 different sequence types. A total of 420 virulence genes were identified of which 260 genes were found in all sequenced L. pneumophila isolates. Virulence genes enhC, htpB, omp28, and mip were detected in all isolates, suggesting that adhesion, at-tachment, and entry into host cells are enabled for all isolates. The relative frequency of viru-lence genes among L. pneumophila isolates was high. High prevalence, extensive genetic diver-sity, and the wide range of virulence genes indicated that the virulence potential of environ-mental Legionella is high and proper risk management is of key importance to public health.