Fatal case of streptococcal prosthetic valve endocarditis caused by Streptococcus mitis in patient with tetralogy fallot disorder: a case report

BACKGROUND: Prosthetic valve Endocarditis (PVE) is an uncommon but potentially life-threatening infection involves a valve prosthesis or annuloplasty ring. Streptococci, including Streptococcus mitis and enterococci are major etiological agents, with studies indicating their significant role in late-onset PVE in some regions of world, staphylococci have surpassed streptococci as the most frequent causative organism. Despite challenges in diagnosis, molecular methods offer high sensitivity. CASE PRESENTATION: A 30-year-old female patient, Iranian, with a history of hypothyroidism, tetralogy of Fallot, and a bioprosthetic valve replacement and weakness after two months from exprience upper respiratory tract infection (URTI), was admitted with complaints of epistaxis, fever and worsening of shortness of breath. She exhibited symptoms of anemia, thrombocytopenia, elevated WBC, LDH, and D-dimer levels, along with splenomegaly, pleural effusions, and pulmonary congestion. Echocardiography revealed significant valve vegetation and RV failure. Despite comprehensive treatment, including cardiac surgery and antifungal therapy, her condition deteriorated, leading to cardiac arrest and death. Posthumous molecular analysis identified S. mitis as the causative agent, despite negative blood cultures. CONCLUSIONS: This case highlights the challenges of diagnosing and treating complex PVE, particularly when conventional cultures are negative. The detection of S. mitis through molecular methods underscores the importance of early and accurate identification of pathogens in guiding effective treatment.