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 of the PCR products indicated that fragments of two genes, designated vanB and ddl, were co-amplified. The vanB gene was previously shown to be present in Enterococcus strains expressing VanB-type Vm(R) [Quintiliani Jr. et al., J. Infect. Dis. 8 (1993) 943-950]. The ddl gene was detected by Southern hybridization in all Vm(R) and Vm(S) strains of En. faecalis, but not in representatives of 17 other species of Enterococcus. The vanB and ddl genes were cloned in bacteriophage h and sequenced. There was extensive similarity (76% aminoacid identity) between the product of vanB and the Vm(R) protein, VanA. The product of ddl, the D-Ala:D-Ala ligases, DdlA and DdlB, of Escherichia coli and the resistance proteins, VanA and VanB, were more distantly related (32-40% aa identity). After induction of Vm(R), En. faecalis V583 synthesized the cell wall precursor, UDP-N-acetylmuramyl-tetrapeptide-D-lactate, indicating that the mechanism of glycopeptide resistance in strains with the VanA and VanB phenotype is similar.