Revisiting the taxonomy of Enterococcus casseliflavus and related species

Enterococcus casseliflavus, a commonly mobile and yellow-colored bacterium, is a commensal member of the gastrointestinal tract. It is occasionally found in cases of bacteremia and other human infections. A concern is that all strains of this species have the vanC gene group on their chromosome, which confers resistance to vancomycin. The classification of E. casseliflavus is challenging, as it presents 99% identity in 16S analysis with E. gallinarum and, mainly, with E. flavescens, often being classified as a single species. This study aimed to revisit the taxonomy of E. casseliflavus and other related species by carrying out a comprehensive analysis of the genomic data available for these species in public databases.analyzing the genomic data. For this, 155 genomes of E. casseliflavus related species (E. casseliflavus, E. flavescens, E. entomosocium, and E. innesii) were retrieved and submitted to Average Nucleotide Identity (ANI) and phylogenomic analysis. Both approaches showed three well-delineated clusters which correspond to three Enterococcus species (E. casseliflavus, E. flavescens and E. innesii). Here we suggest (1) the removal of synonym status between E. flavescens and E. cassliflavus, and (2) addition of synonym status between E. entomosocium and E. casseliflavus.