Genomic Characterization of Linezolid-Resistant Harboring Variants.

The emergence of antimicrobial resistance (AMR) in (), particularly to last-line antibiotics such as linezolid, represents a critical challenge in clinical settings. This study investigates the genomic epidemiology of linezolid-resistant , focusing on the distribution and mutational patterns of the chloramphenicol-florfenicol resistance () gene and its association with multidrug resistance. We analyzed 514 clinical isolates (354 from NCBI Pathogen Detection, 160 from EnteroBase), revealing distinct prevalence patterns among subtypes: (C) was dominant (156/354 NCBI strains; 101/160 EnteroBase strains), whereas (B) frequently harbored missense mutations (p.R247K, p.V294I, and less commonly p.A334T). The (E) subtype was exclusively identified in ribotype 027 (RT027) strains. Notably, (C) exhibited a strong association with RT017, correlating with a conserved 99 bp genomic deletion. Phylogenetic analysis linked -carriage to predominant sequence types (ST1 in NCBI strains, ST37 in EnteroBase isolates). Furthermore, the co-occurrence of with additional AMR genes conferred resistance to macrolides (erythromycin, azithromycin) and tetracyclines, indicating a convergent evolution toward multidrug resistance. These findings underscore the interplay between mutations, hypervirulent ribotypes, and AMR dissemination, necessitating enhanced surveillance to mitigate the spread of resistant lineages.