Whole genome characterization of a naturally occurring vancomycin-dependent Enterococcus faecium from a patient with...

Vancomycin-dependent enterococci are a relatively uncommon phenotype recovered in the clinical laboratory. Recognition and recovery of these isolates are important, to provide accurate identification and susceptibility information to treating physicians. Herein, we describe the recovery of a vancomycin-dependent and revertant E. faecium isolates harboring vanB operon from a patient with bacteremia. Using whole genome sequencing, we found a unique single nucleotide polymorphism (S186N) in the D-Ala-D-Ala ligase (ddl) conferring vancomycin-dependency. Additionally, we found that a majority of in vitro revertants mutated outside ddl, with some strains harboring mutations in vanS, while others likely containing novel mechanisms of reversion.