Enterococcus faecalis is a strain of bacteria that normally appears in the human intestine. It is a common cause of urinary tract infections, pelvic infections and meningitis, notes UpToDate.
Enterococcus faecalis is an aerotolerant anaerobe, meaning that while it does not need oxygen to survive, it is not harmed by the presence of oxygen, notes the ASM Microbe Library. It is most commonly found on the distal end of the urethra and in the small intestine in humans and in certain animals. Enterococcus faecalis is known to cause endocarditis, an infection of the inside surface of the heart, as well as bacterial meningitis, according to UpToDate.
Infections caused by enterococcus faecalis are often difficult to treat because the bacteria is highly resistant to several types of antibiotics, notes The American Society for Microbiology. Penicillin, ampicillin and vancomycin are ineffective against enterococcus faecalis. However, a combination of differently active antibiotics can eradicate an infection. For example, for a patient with a serious condition, such as endocarditis, a doctor might prescribe a combination of ampicillin and streptomycin to destroy the bacteria, according to UpToDate. Urinary tract infections caused by enterococcus faecalis may be slightly easier to treat and require only one antibiotic, notes Merck Manuals.