Characterization of the vanD glycopeptide resistance gene cluster from Enterococcus faecium BM4339. |
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| Authors: | B Casadewall P Courvalin |
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| Affiliation: | Unité des Agents Antibactériens, Institut Pasteur, 75724 Paris Cedex 15, France. |
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| Abstract: | VanD-type resistance to glycopeptides in Enterococcus faecium BM4339 is due to constitutive synthesis of D-alanyl-D-lactate-terminating peptidoglycan precursors (B. Périchon, P. Reynolds, and P. Courvalin, Antimicrob. Agents Chemother. 41:2016-2018, 1997). The sequence of a 5,780-bp fragment was determined and revealed six open reading frames. The 3' distal part encoded the VanHD dehydrogenase, the VanD ligase, and the VanXD DD-dipeptidase, which were highly similar to the corresponding proteins in VanA and VanB types of resistance. The deduced VanYD protein was homologous to penicillin-binding proteins that display DD-carboxypeptidase activity. The 5' end coded for the putative VanRD-VanSD two-component regulatory system. Due to a frameshift mutation in the chromosomal ddl gene, BM4339 produced an impaired D-alanine:D-alanine ligase. However, since expression of the resistance genes is constitutive, growth of E. faecium BM4339 was not dependent on the presence of glycopeptides in the culture medium. |
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