Detection Methods for Glycopeptide-Resistant Staphylococcus aureus II: Cell Wall Analysis

Vancomycin resistance of Mu50 (VRSA) and Mu3 (hetero-VRSA) is associated with the changes in cell-wall synthesis. Therefore, the analysis of cellwall synthesis and cell-wall composition study is of cardinal importance for the understanding of this resistance mechanism. The rate of the cell-wall synthesis can be evaluated by measuring the rate of up-take of 14 C-N-acetylglucosamine into the cell, since more than 95% of 14 C-N-acetylglucosamine is known to be incorporated into the cell wall (1 ). Murein monomer precursor (UDP-N-acetylmuramyl-pentapeptide) (MMP) is an important intermediate substrate of peptidoglycan synthesis, detection, and quantitation of MMP is useful for the investigation of how the cell-wall synthesis system is altered in S. Aureus in association with glycopeptide resistance. For example, the cytoplasmic pool size of MMP is several times greater in Mu50 and Mu3 than in vancomycin-susceptible S. Aureus strains (2 ).