Inhibition of Staphylococcus aureus cell wall biosynthesis by desleucyl-oritavancin: a quantitative peptidoglycan composition analysis by mass spectrometry.

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Inhibition of Staphylococcus aureus cell wall biosynthesis by desleucyl-oritavancin: a quantitative peptidoglycan composition analysis by mass spectrometry.

J Bacteriol. 2017 May 15;:

Authors: Chang JD, Foster EE, Thadani AN, Ramirez AJ, Kim SJ

Abstract
Oritavancin is a lipoglycopeptide antibiotic that exhibits potent activities against vancomycin-resistant Gram-positive pathogens. Oritavancin differs from vancomycin by a hydrophobic side chain attached to the drug disaccharide, which forms a secondary-binding site to enable oritavancin binding to the cross-linked peptidoglycan in cell wall. The mode of action of secondary-binding site was investigated by measuring the changes in the peptidoglycan composition of Staphylococcus aureus grown in presence of desleucyl-oritavancin at sub-inhibitory concentration using liquid chromatography-mass spectrometry (LC-MS). Desleucyl-oritavancin is an Edman degradation product of oritavancin that exhibits potent antibacterial activities despite the damaged d-Ala-d-Ala binding site due to its functional secondary-binding site. Accurate quantitative peptidoglycan composition analysis based on 83 muropeptide ions determined that cell walls of S. aureus grown in the presence of desleucyl-oritavancin showed reduction of peptidoglycan cross-linking, increased muropeptides with a tetrapeptide-stem structure, decreased O-acetylation of MurNAc, and increased N-deacetylation of GlcNAc. The changes in peptidoglycan composition suggest that desleucyl-oritavancin targeted peptidoglycan template to induce cell wall disorder and interfered with cell wall maturation.IMPORTANCE Oritavancin is a lipoglycopeptide antibiotic with a secondary-binding site that targets the cross-linked peptidoglycan bridge structure in the cell wall. Even after the loss of its primary d-Ala-d-Ala binding site through Edman degradation, desleucyl-oritavancin exhibits potent antimicrobial activities through its still functioning secondary-binding site. In this study, we characterize the mode of action for desleucyl-oritavancin's secondary-binding site using LC-MS. Peptidoglycan composition analysis of desleucyl-oritavancin treated S. aureus was performed by determining the relative abundances of 83 muropeptide ions matched from pre-calculated library through integrating extracted ion chromatograms. Our work highlights the use of quantitative peptidoglycan composition analysis by LC-MS to provide insights into glycopeptide antibiotic mode of action.

PMID: 28507244 [PubMed - as supplied by publisher]