Many species in the genus Enterococcus possess intrinsic resistance to commonly used antibiotics. Intrinsic resistance represents naturally encoded chromosomal characteristics that are present in most Enterococci. These resistance mechanisms affect primarily the aminoglycosides and beta lactam antibiotics, and create therapeutic challenges for the treatment of serious infections such as endocarditis or septicemia. In addition to intrinsic resistance, Enterococci can acquire genetic determinants that confer resistance to other antibiotics. The emergence and increasing frequency of vancomycin-resistant Enterococci (VRE) has presented both therapeutic and infection control challenges.