Affiliation:
1. Dipartimento di Scienze e Tecnologie Alimentari per Una Filiera Agro-Alimentare Sostenibile (DISTAS), Università Cattolica del Sacro Cuore, Piacenza-Cremona, Italy
Abstract
Enterococcus lactis
and the heterotypic synonym
Enterococcus xinjiangensis
from dairy origin have recently been identified as a novel species based on 16S rRNA gene sequence analysis.
Enterococcus faecium
type strain NCTC 7171T was used as the reference genome for determining
E. lactis
and
E. faecium
to be separate species. However, this taxonomic classification did not consider the diverse lineages of
E. faecium
, and the double nature of hospital-associated (clade A) and community-associated (clade B) isolates. Here, we investigated the taxonomic relationship among isolates of
E. faecium
of different origins and
E. lactis
, using a genome-based approach. Additional to 16S rRNA gene sequence analysis, we estimated the relatedness among strains and species using phylogenomics based on the core pangenome, multilocus sequence typing, the average nucleotide identity and digital DNA–DNA hybridization. Moreover, following the available safety assessment schemes, we evaluated the virulence profile and the ampicillin resistance of
E. lactis
and
E. faecium
clade B strains. Our results confirmed the genetic and evolutionary differences between clade A and the intertwined clade B and
E. lactis
group. We also confirmed the absence in these strains of virulence gene markers IS16, hylEfm
and esp and the lack of the PBP5 allelic profile associated with ampicillin resistance. Taken together, our findings support the reassignment of the strains of
E. faecium
clade B as
E. lactis
.
Subject
General Medicine,Ecology, Evolution, Behavior and Systematics,Microbiology