Representants of the genus Enterococcus are part of the normal human gut microbiota, some animals, and birds. The Enterococcus out of the organism can survive in different temperature ranges, salinity, pH and resist some detergents as dodecyl-sodium sulfate and bile (Shepard and Gilmore 2000). Phylogenetically the enterococci are divided into 7 clusters resulting finally in 33 species (Naser et al.2005; Köhler 2007). In human infections, E. faecalis and E. faecium are the most prevailing species (>90%). The first is the most commonly isolated, but recently E. faecium has exhibited an important increase as infectious agent (Treitman et al.2005). The enterococcal infection includes surgical wounds, endocarditis, hepatobiliary sepsis, urinary tract infections, bacteremias and neonatal sepsis among the most important (Poh et al.2006). The majority of the enterococcal infections are endogeneous, but the crossed infection occurs mainly in hospitalized patients (Cookson et al. 2006). Enterococcus in USA is the fourth most common cause of nosocomial infection and the third of bacteremia (Biendenbach et al.2004). In Europe these infections are less and represent a 7.2% of the total Martínez-Odrizola et al. (2007).
Enterococcal strains resistant to different antibiotics are a great public health problem, especially in isolated strains from hospital-acquired infections (Hidron et al. 2008). Several genetic studies have described the complex functions related to horizontal gene transfer in enterococcal strains, which partly explains their high antimicrobial resistance (Arthur et al.1993; Clewell et al.1995). Vancomycin was the antimicrobial agent most active against this bacterium, however, today in different parts of the world, isolated enterococcal strains are resistant to vancomycin (Ridwan et al. 2002; Chang et al.2010).
Various factors determine the E. faecalis virulence, outstanding among those on the cellular surface, as the aggregation substance (Agg), the extracellular surface protein (Esp) and some that are excreted out of the bacterial cell as cytolysin and hyaluronidase, among others (Fisher and Phillips 2009; Semedo et al.2003; Koch et al. 2004). Additionally, the Enterococcus spp. synthesizes heterogeneous antibacterial peptides or bacteriocins, also called enterocins (Giraffa 1995). These products may give these bacteria an additional ecological tool to persist in environments colonized by competing microorganisms in order to remove them and take over the ecological niche (Padilla et al. 2006).
In recent years, E. faecalis has a greater ability to cause infections on different human epithelia (Fisher and Phillips 2009). Thus, more studies are needed to provide new knowledge about this bacterial specie
Currently, there is considerable information regarding the antimicrobial susceptibility, presence of virulence genes and bacteriocins in E. faecalis strains isolated from clinical specimens and food. However, it would also be important to study if strains that come from water wells possess the properties mentioned and if it is possible to transmit these characteristics to the intestinal microbiota of people who drink this water.
Is important to remark that in some rural areas of central Chile, where there is no drinking water, people use well water for drinking and for various domestic purposes.
For a better understanding of the biology of E. faecalis, the objectives of this study were to detect genes for virulence and bacteriocins in addition to studying the antimicrobial susceptibility of 78 strains of E. faecalis isolated from water wells for human consumption.