Enterococcus are bacteria, belonging among the Firmicutes. They are round gram-positive cells which occur in pairs and are difficult to distinguish from Streptococcus. Two species are common commensal[?] organisms in the intestines of humans: E. faecalis and E. faecium. They are anaerobic, not requiring oxygen to live but can survive in the presence of oxygen. Important clinical infections caused by Enterococcus are urinary tract infection, bacteremia[?], bacterial endocarditis[?], diverticulitis[?], wound infections[?] and rarely meningitis. This bug is usually sensitive to ampicillin and vancomycin. During the last decade, a particularly virulent strain of Enterococcus has plagued hospitalized patients., which is resistant to both ampicillin and vancomycin.