ANALYSIS OF PEPTIDOGLYCAN PRECURSORS IN VANCOMYCIN-RESISTANT ENTEROCOCCI

Analysis by high-pressure liquid chromatography of the cytoplasmic peptidoglycan precursors of a high- and a low-level vancomycin-resistant Enterococcus spp. was performed before and after induction of resistance. This analysis showed a decrease of the D-Ala-D-Ala and UDP-MurNac-pentapeptide pools, an increase of the UDP-MurNac-tripeptide pool, and the appearance of new UDP-MurNac-containing material. These results lead us to suggest that the vancomycin-induced carboxypeptidase activity cleaves the D-Ala-D-Ala (L. Gutmann, D. Billot-Klein, S. Al-Obeid, I. Klare, S. Francoul, E. Collatz, and J. van Heijenoort, Antimicrob. Agents Chemother. 36:77-80, 1992), which in turn would prevent formation of the normal UDP-MurNac-pentapeptide and thereby of the vancomycin target. The novel UDP-MurNac-containing material is thought to correspond to peptidoglycan precursors which might be synthesized by an alternate pathway (T. D. H. Bugg, G. D. Wright, S. Dutka-Malen, M. Arthur, P. Courvalin, and C. T. Walsh, Biochemistry 30:10408-10415, 1991) and which would be unable to bind vancomycin in glycopeptide-resistant enterococci.