Introduction: S. salivarius is a gram-positive bacterium which primarily and predominantly colonizes oral cavity and intestines but is also proven to have infectious capacity. It is a member of viridans bacteria species which cause 40% of endocarditis but it is important to note that S. salivarius alone causes bacterial endocarditis in only 2% of cases (1, 2).

Case report: 28-year-old patient is hospitalized in General Hospital (GH) Pula because of the 3-week long febrility. In 2015 the patient was diagnosed with the posterior mitral cusps prolapse with moderate to severe mitral regurgitation and atrial septal defect with left-to-right shunt. An operation was suggested but the patient was not prone to it. Echocardiography verified the diagnosis of endocarditis of both mitral cusps with severe mitral regurgitation. An MSCT of the abdomen showed splenic and renal infarct. The next day the patient was transferred to University Hospital (UH) “Dubrava” Zagreb where he underwent a mechanical mitral valve replacement surgery on July 15, 2024. The operation went well and the patient was transferred back to GH Pula. During the hospitalization the patient indicated the pain in the lower abdomen and constipation. The MSCT of the abdomen revealed newly grown porta hepatis mass. On July 31, 2024 the patient was transferred to UH “Merkur” Zagreb. Due to the decline in liver function and the occurrence of encephalopathy a request was sent to Eurotransplant asking to categorize this patient as high-urgency for liver transplant. The liver transplant was done on August 3, 2024.

Conclusion: A patient with mitral cusps prolapse, prolonged febrility, and confirmed bacterial infection is at risk of endocarditis. The patient in question had 1 major and 3 minor Duke Criteria that clearly indicated infective endocarditis. Although S. salivarius rarely causes endocarditis, we must not forget it is potentially very infectious for cerebrovascular, cardiovascular, musculoskeletal, and gastrointestinal system (3).