Enterococci are gram-positive cocci occurring singly, in pairs, or chains; cells can be ovoid to coccobacilli. They are catalase negative or weakly catalase positive organisms. There are over twenty species in the genus, categorized into five major groups. Enterococcus faecalis is the most frequently isolated species. Enterococcus faecium, although less frequently encountered, is also a significant pathogen.
The enterococci are widespread in nature; in humans, they primarily colonize the gastrointestinal tract but are also found in the genitourinary tract. Enterococci are frequently encountered in urinary tract infections; they may also be isolated from wound infections and blood cultures. In addition, these organisms comprise an important cause of endocarditis.
