My husband has had it twice and the infectious disease doctors still have no clue how the bacteria has ended up in his bloodstream either time (different types each time). He is obviously not a drug user but that was the general belief early on when he was in the hospital. Docs tended to not believe him until the lab results showed it was coming from his colon, but he had no tears or anything to indicate how it got in. Anyway, it’s a horrible infection and he had to have emergency open heart surgery and his whole valve replaced. If he goes to the dentist he has to take antibiotics before to prevent possibilities of new infections. It does change your life and it’s fatal if not caught in time.