The Effects of Vancomycin on the Structure of Cell Wall Peptidoglycan of vanB-type Vancomycin-Resistant Enterococcus faecalis by Liquid Chromatography-Mass Spectrometry

Abstract

Enterococcus faecalis is a leading cause of nosocomial infections, and the clinical emergence of vancomycin-resistant E. faecalis (VRE) makes studying this bacterium increasingly urgent. This study investigates a vanB-type strain of VRE (ATCC 51299), which is vancomycin-resistant upon vancomycin’s induction of the vanB operon and subsequent changes in the structure of cell wall peptidoglycan that result in reduced affinity of vancomycin for peptidoglycan. This study explored the effects of vancomycin (at 6 μg/mL) on peptidoglycan structure of VRE using a novel approach that involved a combinatorial, in silico peptidoglycan mass library paired with liquid chromatography-mass spectrometry. In addition to observing the vanB-related changes of the presence of terminal D-Ala-D-Lac and increased D,D-carboxypeptidase activity, increased L,D carboxypeptidase activity and increased O-acetylation were also observed upon the presence of vancomycin, findings which suggest additional mediating roles of vancomycin in the creation and editing of cell wall peptidoglycan.