Infective Endocarditis in Intravenous Drug Abusers

In intravenous drug abusers Staph aureus accounts for 50% of cases of infective endocarditis, with other causes being enterococci (10%), Strep viridans (5%), gram negative bacteria (5%), other bacteria (5%), fungi (5%) and polymicrobial infection (5%). Coagulase-negative staphylococci account for less than 5%.

By contrast, in patients who do not abuse drugs intravenously (and do not have prosthetic valves) the frequency of infection is as follows: Strep viridans 35%, enterococci 25%, Staph aureus 23%, culture negative 5-10%, other identified organisms 5-10%.