A 82-year-old woman with a past history of aortic valve replacement, mitral annuloplasty and pacemaker implantation was admitted to a hospital due to weakening, subfebrile state and chills. The findings of transesophageal echocardiography revealed vegetations on the aortic valve bioprosthesis, but pacemaker electrodes and mitral annulus were not involved in the endocarditis process. Bacteriological work-up showed growth of Lactobacillus gasseri. What should be the treatment plan?