[Genetic characteristics analysis of legionella isolated from environmental water in Beijing from 2023 to 2024].

Bioinformatics approaches were employed to analyze 67 Legionella isolates collected from four districts of Beijing between 2023 and 2024, aiming to characterize the genomic features, virulence potential, and antimicrobial resistance mechanisms of Legionella, thereby providing data support for regional prevention and control strategies. All isolates were serotyped and confirmed by PCR, followed by whole-genome sequencing and assembly. Virulence and antibiotic resistance genes were predicted, and genetic typing of strains was performed based on multilocus sequence typing (MLST). A phylogenetic tree was constructed using the maximum likelihood method based on single nucleotide polymorphisms (SNPs). The results showed that LP1 was the predominant serogroup, accounting for 40.29% (27/67) of isolates. Genome sizes ranged from 3.06 to 3.97 Mb, with GC content ranging from 38.17% to 38.75%. ST1 was the dominant sequence type, accounting for 26.15% (17/65), followed by ST242 (13.85%, 9/65). All isolates carried four major virulence-associated factors, including Dot/Icm type Ⅳ secretion system effectors, CcmC, CsrA, and LetA/S. A total of five antimicrobial resistance genes were identified, mainly associated with resistance to aminoglycosides and macrolides. Notably, the multidrug resistance genes lpeA/lpeB were detected in 25.37% (17/67) of isolates, with 94.12% (16/17) of these belonging to ST1 and 88.24% (15/17) to LP1. In conclusion, the ST1-LP1 clonal complex represents the predominant circulating lineage in the region and is associated with a relatively high prevalence of lpeA/lpeB, suggesting its potential for enhanced transmission and pathogenic risk.