**1. Introduction**

Enterococci (ENT), the Gram-positive (G +ve), catalase negative, benzidine negative, non-spore forming and aero-tolerant fermentative organisms form the second largest group of bacteria studied with reference to microbial source tracking (MST) [1, 2]. It is a non-filamentous microorganism but some species like *E. casseliflavus* and *E. gallinarum* exhibit motility by scanty flagella. They produce lactic acid [L (+)- lactic acid enantiomer in case of glucose fermentation] by homofermentative Embden-Meyerhof-Parnas pathway, hence called Lactic Acid Bacteria (LAB). All the species except *E. faecalis* [(*E. fl*) (which contains lysine alanine 2–3 type)] contains lysine-D-asparagine linkages with D-isoasparagine as cross bridge in peptidoglycan. Their ability to survive in adverse environmental conditions and adaptable nature revolutionize them from low number commensals to a predominant population of host microbiota which ultimately results in creating a consequence for their pathogenesis [3]. Despite being a member of normal human intestinal flora, they are not regarded as GRAS (Generally Recognized As Safe) organisms anymore [4] as some of its species have turned out to be a major cause of nosocomial infections including hepatobiliary sepsis, urinary tract infections (UTI), surgical wound infections, endocarditis, bacteremia and neonatal sepsis [5]. From a medical perspective, ENT have been recognized as an important hospital acquired pathogen due to their ability to transfer or acquire resistance genes via

**Figure 1.** *Bacterial mobile genetic elements.*

chromosomal exchange as well as plasmid or transposon (**Figure 1**). This can lead to increment in dangerous nosocomial infections, thus limiting therapeutic options [6]. This is the reason for exploitation of this genus as an important key indicator bacterium for humans and veterinary resistance surveillance system [7].
