Sequencing the gene encoding manganese-dependent superoxide dismutase for rapid species identification of enterococci

Simple PCR and sequencing assays that utilize a single pair of degenerate primers were used to characterize a 438-bp-long DNA fragment internal (sodA(int)) to the sodA gene encoding the manganese-dependent superoxide dismutase in 19 enterococcal type strains (Enterococcus avium, Enterococcus casseliflavus, Enterococcus cecorum, Enterococcus columbae, Enterococcus dispar, Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus flavescens, Enterococcus gallinarum, Enterococcus hirae, Enterococcus malodoratus, Enterococcus mundtii, Enterococcus pseudoavium, Enterococcus raffinosus, Enterococcus saccharolyticus, Enterococcus seriolicida, Enterococcus solitarius, and Enterococcus sulfureus). Sequence analysis of the sodA(int) fragments enabled reliable identification of 18 enterococcal species, including E. casseliflavus-E. flavescens and E. gallinarum. The sodA(int) fragments of E. casseliflavus and E. flavescens were almost identical (99.5% sequence identity), which suggests that they should be associated in a single species. Our results confirm that the sodA gene constitutes a more discriminative target sequence than 16S rRNA gene in differentiating closely related bacterial species.