**4. Lineages of nosocomial Enterococci**

The ability of *E. faecium* to exchange mobile genetic elements carrying antimicrobial resistance genes and virulence determinants has resulted in hospital adapted clones [24]. Esp was the first adaptive element found in hospital strains of *E. faecium*. The *E. faecium* esp. gene has been linked to biofilm formation, UTI and endocarditis [24]. New determinants have been now linked to hospital isolates of *E. faecium*. A genomic analysis study of *E. faecium* hospital strains identified gain and loss of gene clusters in clinical and non-clinical isolates of *E. faecium* [25]. Genomic studies of nosocomial *E. faecium* infection have confirmed the transmission of *E. faecium* Clad A115. Recently it has been seen a significant presence of hospital associated VRE fm lineages in the wastewater and need of controlling healthcare associated dissemination of VRE fm [26]. However studies on *E. faecalis* ecotypes have shown no appearance of distinct *E. faecalis* strains over a significant period of time. Virulence factors like antibiotic resistance and virulence genes, esp., capsule polysaccharide genes and genes determining gelatinase, aggregation factor, cytolysin and ace are identified in *E. faecalis* isolates [27]. The non-emergence of distinct ecotypes of *E. faecalis* and multiplicity of closely related ecotypes is not seen in *E. faecalis* as compared to *E. faecium*. A genomic analysis of 168 *E. faecalis* hospital isolates showed no genes and non-synonymous single nucleotide polymorphisms in the three lineages of hospital strains [28]. A recent study has also demonstrated that the acquisition of mobile genetic elements in *E. faecalis* V583, makes it unable to coexist with commensal enterococci in humans [29].
