Related Experiment Video
Updated: Feb 14, 2026

A 1.5 Hour Procedure for Identification of Enterococcus Species Directly from Blood Cultures
Published on: February 10, 2011
Transferable vancomycin resistance in clade B commensal-type Enterococcus faecium
François Lebreton1,2, Michael D Valentino1,2, Katharina Schaufler1,2
1Departments of Ophthalmology, Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.
Objectives:
Vancomycin-resistant Enterococcus faecium is a leading cause of MDR hospital infection. Two genetically definable populations of E. faecium have been identified: hospital-adapted MDR isolates (clade A) and vancomycin-susceptible commensal strains (clade B). VanN-type vancomycin resistance was identified in two isolates of E. faecium recovered from blood and faeces of an immunocompromised patient. To understand the genomic context in which VanN occurred in the hospitalized patient, the risk it posed for transmission in the hospital and its origins, it was of interest to determine where these strains placed within the E. faecium population structure.
Methods:
We obtained the genome sequence of the VanN isolates and performed comparative and functional genomics of the chromosome and plasmid content.
Results:
We show that, in these strains, VanN occurs in a genetic background that clusters with clade B E. faecium, which is highly unusual. We characterized the chromosome and the conjugative plasmid that carries VanN resistance in these strains, pUV24. This plasmid exhibits signatures of in-host selection on the vanN operon regulatory system, which are associated with a constitutive expression of vancomycin resistance. VanN resistance in clade B strains may go undetected by current methods.
Conclusions:
We report a case of vancomycin resistance in a commensal lineage of E. faecium responsible for an atypical bacteraemia in an immunocompromised patient. A reservoir of transferable glycopeptide resistance in the community could pose a concern for public health.
Related Concept Videos
Types of Genetic Transfer Between Organisms
Types of Genetic Transfer Between Organisms
Resistivity
Resistance
Equivalent Resistance
Resistance and Conductance
Various factors impact the resistance of a conductor. Spiraling in stranded conductors increases their...

