I have had endocarditis twice—just over a year apart. Bothe were strep but different strains. Infectious disease dr insisted that strep comes from the mouth. But I had a full dental checkup and there were no problems. So they decided to put me on Keflex twice a day—probably for the rest of my life. I have no side effects and doc said this is a good antibiotic to be on. Also stopped flossing and use water pic instead. I use listerene before brushing my teeth. It has been over 3 years since my 2nd endocarditis.