Background: A 26-year-old man with known but untreated ventricular septal defect was admitted to the emergency ward with abdominal pain, fever and weight loss. Transthoracic echocardiography showed multiple vegetations on the anterior mitral leaflet, a mobile vegetation on the surface of the aortic noncoronary cusp and another on the tricuspid valve. His blood cultures grew Streptococcus sanguis with a penicillin minimum inhibitory concentration of 3 microg/ml.
Investigations: Physical examination, echocardiography, blood cultures, minimal inhibitory concentration detection.
Diagnosis: Multivalvular infective endocarditis caused by S. sanguis with a high penicillin resistance.
Management: A combination of intravenous vancomycin and gentamicin, followed by early surgery.