Enterococcus faecalis bacteria, coloured scanning electron micrograph (SEM). Enterococcus faecalis is a Gram-positive, spherical (coccus) bacterium found in the gastrointestinal tracts of human and other mammals, but may cause infections in the urinary tract. It may cause bacterial endocarditis in infants and in adults after gynaecological or genito-urinary surgery. It can also cause pneumonia. E. faecalis has a natural resistance to many antibiotics, making it one of the so called superbugs. Magnification: x10,000, when printed 15cm wide.