Genomic characteristics and drug resistance phenotype of Levyella massiliensis isolated from blood

This study reports the first isolation of a strain of Levyella massiliensis (strain HGL1) from human blood samples in China. Currently, the genomic characteristics, antibiotic resistance, and pathogenic potential of this species have not been fully studied. To systematically decipher the phylogenetic position, genomic composition, and potential pathogenicity-related factors of strain HGL1, this study employed a dual-platform sequencing strategy (PacBio Sequel II and Illumina NovaSeq PE150) for whole-genome sequencing of strain HGL1 and assessed its antibiotic susceptibility through antimicrobial susceptibility testing. Phylogenetic analysis revealed that strain HGL1 and L. massiliensis D22-N-7-79 reside within the same evolutionary clade, with an Average Nucleotide Identity (ANI) of 97.88% and a digital DNA-DNA hybridization (dDDH) value of 80%, supporting the classification of strain HGL1 as a member of L. massiliensis. Genomic analysis indicated that the HGL1 genome is 1,682,293 bp in size with a GC content of 48.85%, harboring a total of 1,613 predicted coding genes, 56 potential virulence genes, and 4 antibiotic resistance genes. Antimicrobial susceptibility testing results showed that this bacterium is susceptible to tigecycline, amoxicillin/clavulanic acid, and some β-lactam antibiotics; however, it exhibits resistance to macrolides (e.g., erythromycin, clarithromycin, azithromycin), trimethoprim/sulfamethoxazole, third-generation cephalosporins (ceftriaxone, cefotaxime), quinolones (ciprofloxacin, levofloxacin), and gentamicin. These findings demonstrate that L. massiliensis HGL1 is a bacterium possessing multidrug resistance and potential human pathogenicity. In-depth analysis of its genomic characteristics and resistance phenotype provides a scientific basis for understanding the biology and combating infections caused by this rare pathogen, underscoring the necessity for enhanced surveillance and research on this bacterium in future clinical practice.