Title : From oral flora to embolic disease: A case of streptococcus salivarius endocarditis presenting with splenic infarction in a young patient
Abstract:
Background: Streptococcus salivarius is a viridans group streptococcus that forms part of the normal oral flora and is a rare cause of infective endocarditis (IE). Cases are typically associated with poor dentition, dental procedures, or underlying structural cardiac disease. Splenic infarction is an uncommon presentation of IE and may delay diagnosis when an embolic source is not immediately recognised.
Case: A man in his twenties with bicuspid aortic valve and poor dentition presented with a one-month history of malaise, gastrointestinal symptoms, and worsening abdominal pain. Initial computed tomography (CT) demonstrated a splenic lesion suspicious for infarction. Subsequent magnetic resonance imaging confirmed multifocal splenic and left renal infarcts, including new lesions compared with the original CT, raising suspicion for an embolic process.
The patient re-presented one week later with worsening symptoms. Blood tests demonstrated elevated inflammatory markers, troponin, and D-dimer. Examination identified a loud ejection systolic murmur not documented previously. Repeated blood cultures isolated Streptococcus salivarius. Transthoracic echocardiography demonstrated vegetations on the aortic and mitral valves with moderate aortic regurgitation and suspicion of an aortic root abscess. Transoesophageal echocardiography subsequently confirmed an aortic root abscess, fulfilling Modified Duke criteria for infective endocarditis. The patient was commenced on intravenous antibiotics and referred for cardiothoracic surgical management.
Discussion: This case highlights Streptococcus salivarius as a rare but clinically significant cause of infective endocarditis presenting with systemic embolisation. Although generally considered a low-virulence oral commensal, S. salivarius can cause severe invasive infection in patients with structural valve disease and poor dentition.
While viridans streptococci are common causes of IE, S. salivarius represents only a small proportion of streptococcal endocarditis cases and may therefore be overlooked as a contaminant. In this case, repeated positive blood cultures alongside echocardiographic findings confirmed clinically significant infection complicated by splenic and renal infarction and aortic root abscess formation.
This case also demonstrates the importance of considering infective endocarditis in patients presenting with unexplained visceral infarction, particularly younger patients with congenital valve abnormalities. Earlier echocardiography following identification of embolic infarction may expedite diagnosis and management.
