Reevaluation of the taxonomic status of recently described species of Enterococcus: evidence that E. thailandicus is a senior subjective synonym of "E. sanguinicola" and confirmation of E. caccae as a species distinct from E. silesiacus

Abstract

Several of the more recently proposed new species of Enterococcus are nearly identical based on 16S rRNA gene sequence analysis and phenotypic traits. In the present study, DNA-DNA reassociation experiments, in conjunction with sequencing of the 16S rRNA and rpoB genes, provided evidence that "Enterococcus sanguinicola" and Enterococcus thailandicus actually represent the same species. In contrast, Enterococcus caccae and Enterococcus silesiacus, two other species with nearly identical 16S rRNA gene sequences, were confirmed to be separate species.

Fig. 1.

Phylogenetic trees based on comparative analysis of the 16S rRNA (A) or rpoB (B) gene sequences, showing the relationships among the type strains of Enterococcus sanguinicola, Enterococcus thailandicus, Enterococcus caccae, Enterococcus silesiacus, and other selected species of Enterococcus. GenBank accession numbers are given in parentheses. The neighbor-joining method was used to create the dendrograms, and 1,000 resamplings at the nodes are displayed as percentages. Scale bars indicate numbers of substitutions per nucleotide position. V. fluvialis, Vagococcus fluvialis.