Long-term carriage and evolution of VREfmLong-term carriage and evolution of vancomycin-resistant Enterococcus faecium: a genomic study on consecutive isolates.

ABSTRACT

Objectives: To determine if vancomycin-resistant Enterococcus faecium (VREfm) carriers carry the same VREfm clone after a minimum follow-up of 365 days. For those carrying the same clone, we investigated the genomic evolution per year per genome. Methods: We used WGS results to assign VREfm clones to each isolate and determine clone shifts. Finally, we calculated distance in core-genome MLST alleles, and the number of SNPs between consecutive VREfm isolates from patients carrying the same VREfm clone. Results: In total, 44.2% of patients carried the same VREfm clone, and the genomic evolution was 1.8 alleles and 2.6 SNPs per genome per year. Conclusions: In our population of long-term carriers, we calculated a molecular clock of 2.6 SNPs.