Characterization of a Novel Species of Legionella Isolated from a Healthcare Facility: Legionella resiliens sp. nov.

Two Legionella -like isolates, 8cVS16T and 9fVS26, were isolated from a water distribution system (WDS) in a healthcare facility. Cells were Gram- and Ziehl Neelsen-stain-negative, rod-shaped, motile, and exhibited a blue-white fluorescence under Wood's lamp at 365 nm. The strains grew in a range of 32-37 °C on BCYE with L-cysteine (C ys +), GVPC, and MWY agar medium, with a positive reaction for oxidase, catalase, and gelatinase. The dominant fatty acids were summed features 3 (C16:1 ω7c/C16:1 ω6c) (27.7%), C16:0 iso (17.5%), and C16:0 (16.3%), and Q13 as the major ubiquinone. The mip and rpoB gene sequences showed a similarity of 96.7% and 92.4%, with L. anisa (ATCC 35292T ). The whole genomes sequencing (WGS) performed displayed a GC content of 38.21 mol% for both. The digital DNA-DNA hybridization (dDDH) analysis demonstrated the separation of the two strains from the phylogenetically most related L. anisa ( ATCC 35292T ), with ≤43% DNA-DNA relatedness. The Average Nucleotide Identity (ANI) between the two strains and L. anisa (ATCC 35292T ) was 90.74%, confirming that the two isolates represent a novel species of the genus Legionella . The name proposed for this species is Legionella resiliens sp. nov., with 8cVS16T (=DSM 114356T = CCUG 76627T ) as the type strain.