An Outbreak of ST80 Vancomycin-Resistant <i>Enterococcus faecium</i> in a Hospital in Guangzhou, China: Clinical and Genomic Epidemiology Study from 2022 to 2023

A notable increase in the incidence of vancomycin-resistant <i>Enterococcus faecium</i> (VREfm) was observed at a hospital in Guangzhou, China, during 2022-2023. We conducted a retrospective cross-sectional study from January 1, 2022, to August 31, 2023, to investigate the clinical and genomic characteristics of VREfm. Clinical data were extracted from electronic medical records, and infection control measures were reviewed from the relevant department. VREfm confirmation was performed using antimicrobial susceptibility testing. Genomic characteristics were analyzed via the whole-genome sequencing. The prevalence of VREfm among <i>E. faecium</i> isolates rose significantly from 13.3% (10/75) in 2022 to 26.4% (40/151) by August 2023 (<i>p</i> < 0.001). Concurrently, usage of third-generation cephalosporins increased by 8.4% (22.47 to 24.36 defined daily doses per 100 patient days), carbapenems by 34% (51.47-68.97), and vancomycin by 18% (21.15-24.97) (all <i>p</i> ≤ 0.001). Molecular analysis revealed ST80/CC17 (78%, 39/50) as the dominant clone, carrying <i>vanA</i> and virulence genes (<i>scm</i>, <i>acm,</i> and <i>fss3</i>), suggesting clonal expansion of a lineage rarely reported in Guangzhou. Our study documented an outbreak of ST80/CC17 <i>vanA</i>-positive VREfm, characterized by virulence genes (<i>scm</i>, <i>acm,</i> and <i>fss3</i>) and clonal dominance (78%, 39/50). The temporal association between reduced sodium hypochlorite disinfection (2.7-fold decline, <i>p</i> = 0.002), increased antibiotic selective pressure, and pathogen transmission highlights multifactorial drivers of this epidemic. These findings underscore the complex multifactorial nature of pathogen transmission, including the role of antibiotic use, infection control measures, and environmental factors in the spread of multidrug-resistant clones. Strengthened infection control strategies-integrating targeted disinfection, antibiotic stewardship, and genomic surveillance-are imperative to curb the spread of such multidrug-resistant clones.