Emergence and ongoing outbreak of ST80 vancomycin-resistantEnterococcus faeciumin Guangdong province, China from 2021 to 2023: a multicenter, time-series and genomic epidemiological study

Background The surveillance system revealed that the prevalence of vancomycin-resistant Enterococcus faecium (VREfm) has increased. We aim to investigate the epidemiological and genomic characteristics of VREfm in China. Methods We collected 20747 non-redundant E. faecium isolates from inpatients across 19 hospitals in six provinces between Jan 2018 and June 2023. VREfm was confirmed by antimicrobial susceptibility testing. The prevalence was analyzed using changepoint package in R. Genomic characteristics were explored by whole-genome sequencing and bioinformatic analysis. Results 5.59% (1159/20747) of E. faecium isolates were resistant to vancomycin. The prevalence of VREfm increased in Guangdong province from 5% before 2021 to 20%-50% in 2023 (p<0.0001), but not in the other five provinces. The two predominant clones before 2021, ST17 and ST78, were substituted by an emerging clone, ST80, from 2021 to 2023 (88.63%, 195/220). All ST80 VREfm from Guangdong formed a single lineage (SC11) and were genetically distant from the ST80 VREfm from other countries, suggesting a regional outbreak. All ST80 VREfm in SC11 carried a new type of plasmid which harbored a vanA cassette ( vanRSHAXYZ ) flanked by Tn 1546 /Tn 3 clusters. However, no conjugation-related gene was detected and no transconjugant was obtained in conjugation experiment, indicating that the outbreak of ST80 VREfm could be attributed to clonal transmission. Conclusions We revealed an ongoing outbreak of ST80 VREfm with a new vanA -harboring plasmid in Guangdong, China. This clone has also been identified in other provinces and countries, foreboding a risk of wider spreading shortly. Continuous surveillance is needed to inform public health interventions.