SEQUENCE OF THE VANB AND DDL GENES ENCODING D-ALANINE-D-LACTATE AND D-ALANINE-D-ALANINE LIGASES IN VANCOMYCIN-RESISTANT ENTEROCOCCUS-FAECALIS V583

A pair of degenerate oligodeoxyribonucleotides was used to amplify, by the polymerase chain reaction (PCR), DNA fragments internal to genes encoding D-Ala:D-Bla ligase-related proteins of vancomycin-resistant ( Vm(R)) Enterococcus faecalis V583. Cloning and nucleotide sequencing o f the PCR products indicated that fragments of two genes, designated v anB and ddl, were co-amplified. The vanB gene was previously shown to be present in Enterococcus strains expressing VanB-type Vm(R) [Quintil iani Jr. et al., J. Infect. Dis. 8 (1993) 943-950]. The ddl gene was d etected by Southern hybridization in all Vm(R) and Vm(S) strains of En . faecalis, but not in representatives of 17 other species of Enteroco ccus. The vanB and ddl genes were cloned in bacteriophage h and sequen ced. There was extensive similarity (76% aminoacid identity) between t he product of vanB and the Vm(R) protein, VanA. The product of ddl, th e D-Ala:D-Ala ligases, DdlA and DdlB, of Escherichia coli and the resi stance proteins, VanA and VanB, were more distantly related (32-40% aa identity). After induction of Vm(R), En. faecalis V583 synthesized th e cell wall precursor, UDP-N-acetylmuramyl-tetrapeptide-D-lactate, ind icating that the mechanism of glycopeptide resistance in strains with the VanA and VanB phenotype is similar.