Sabri M. Naser,  Fabiano L. Thompson, Bart Hoste, Dirk Gevers, Peter Dawyndt, Marc Vancanneyt & Jean Swings

The aim of our study was to evaluate the use of RNA polymerase alpha subunit (rpoA) and phenylalanyl-tRNA synthase (pheS) gene sequences as species identification tools for enterococci. Ninety-six representative strains comprising all currently recognized Enterococcus species were examined. rpoA gene sequences generated a robust classification into species groups similar to the one based on the 16S rRNA gene sequence analysis. On the other hand, pheS gene is a fast evolving clock even better suited for species delineation than rpoA gene, but not for recognition of the species groups within Enterococcus as determined by both rpoA and 16S rRNA genes. All enterococcal species were clearly differentiated on the basis of rpoA and pheS sequences. Evaluation of the intraspecies variation showed that both rpoA and pheS genes had a high degree of homogeneity among strains of the same species. Strains of the same enterococcal species have at least 99 % rpoA and 97 % pheS gene sequence similarity, whereas, different enterococcal species have at maximum 97 % rpoA and 86 % pheS gene sequence similarity. We can conclude that both genes can be used as reliable tools for identification of clinical and environmental species of Enterococcus and are efficient screening methods for detection of novel species. The sequence data obtained in this study was compared to the available atpA and 16S rRNA gene sequences. The MLSA approach of Enterococcus provides portable, highly reproducible data with lower costs for rapid identification of all enterococcal species.