Characterization of the vanD glycopeptide resistance gene cluster from Entercoccus faecium BM4339

VanD-type resistance to glycopeptides in Enterococcus faecium BM4339 is due to constitutive synthesis of D-alanyl-D-lactate-terminating peptidoglycan precursors (B. Perichon, P. Reynolds, and P. Courvalin, Antimicrob. Agents Chemother, 41:2016-2018, 1997), The sequence of a 5,780-bp fragment was det ermined and revealed six open reading frames. The 3' distal part encoded th e VanH(D) dehydrogenase, the VanD ligase, and the VanX(D) DD dipeptidase, w hich were highly similar to the corresponding proteins in VanA and VanB typ es of resistance. The deduced VanY(D) protein was homologous to penicillin- binding proteins that display DD-carboxypeptidase activity. The 5' end code d for the putative VanR(D)-VanS(D) two-component regulatory system. Due to a frameshift mutation in the chromosomal ddl gene, BM4339 produced an impai red D-alanine:D-alanine ligase, However, since expression of the resistance genes is constitutive, growth of E. faecium BM4339 was not dependent on th e presence of glycopeptides in the culture medium.