Identification of enterococci at the species level by sequencing of the genes for D-alanine:D-alanine ligases

A PCR assay based on the use of degenerate oligodeoxyribonucleotides allowed characterization of a fragment internal to the dill genes encoding D-alanine:D-alanine ligases in Enterococcus columbae, E. durans, E. malodoratus, E. mundtii, E. raffinosus, E. seriolicida, E. solitarius, and E. sulfureus. Phylogenetic analysis of the sequence of the amplification products and of those already obtained from E. avium, E. casseliflavus, E. cecorum, E. dispar, E. faecalis, E. faecium, E. flavescens, E. gallinarum, E. hirae, E. pseudoavium, and E. saccharolyticus yielded an evolutionary tree with a topology similar to that based on 16S rRNA sequences. Partial sequencing of the ddl gene can therefore be used for genotypic identification of Enterococcus spp.