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Altered peptidoglycan composition in vancomycin-resistant Enterococcus faecalis
B L de Jonge1, S Handwerger, D Gage
1Laboratory of Microbiology, Rockefeller University, New York, New York 10021, USA.
Abstract:
The muropeptide compositions of isogenic vancomycin-resistant and -susceptible Enterococcus faecalis strains were analyzed by reverse-phase high-performance liquid chromatography combined with amino acid analysis and fast atom bombardment mass spectrometry. Peptidoglycan of the susceptible strain contained pentapeptides as stem peptides, whereas peptidoglycan of the isogenic resistant strain was composed of muropeptides with tetrapeptide stem peptides. Despite the synthesis of lactate-terminating peptidoglycan precursors, no lactate-containing muropeptides were detected in peptidoglycan of the resistant strain. These findings indicate that either lactate-terminating precursors are not incorporated into peptidoglycan of the resistant strain or that the lactate residues are removed from peptidoglycan during synthesis.
Insights
Vancomycin resistance in Enterococcus faecalis alters peptidoglycan structure. Resistant strains incorporate tetrapeptide stem peptides instead of pentapeptides, and lack lactate residues despite precursor synthesis.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Enterococcus faecalis is a common cause of hospital-acquired infections.
- Vancomycin resistance in E. faecalis is a growing public health concern.
- Peptidoglycan is a crucial component of bacterial cell walls, targeted by antibiotics like vancomycin.
Purpose of the Study:
- To investigate the muropeptide composition differences between vancomycin-susceptible and -resistant Enterococcus faecalis strains.
- To elucidate the structural changes in peptidoglycan associated with vancomycin resistance.
Main Methods:
- Analysis of muropeptide composition using isogenic strains.
- Employing reverse-phase high-performance liquid chromatography (RP-HPLC).
- Utilizing amino acid analysis and fast atom bombardment mass spectrometry (FAB-MS).
Main Results:
- Vancomycin-susceptible E. faecalis peptidoglycan contained pentapeptide stem peptides.
- Isogenic vancomycin-resistant E. faecalis peptidoglycan featured tetrapeptide stem peptides.
- Lactate-terminating peptidoglycan precursors were synthesized but not detected in the resistant strain's peptidoglycan.
Conclusions:
- Vancomycin resistance in E. faecalis is associated with a shift from pentapeptide to tetrapeptide stem peptides in peptidoglycan.
- The absence of lactate residues in the resistant strain suggests impaired precursor incorporation or post-synthesis modification.
- These findings provide insights into the structural adaptations of bacteria conferring antibiotic resistance.