From diagnostic dilemma to successful management: Early prosthetic mitral valve endocarditis complicated by splenic infarction caused by Klebsiella pneumoniae

Early prosthetic valve endocarditis caused by Gram-negative bacilli is an uncommon but life-threatening condition associated with significant diagnostic and therapeutic challenges. We report the case of a 51-year-old woman who underwent mechanical mitral valve replacement for rheumatic mitral stenosis and presented 1 month later with persistent fever and profound asthenia. Laboratory investigations revealed a marked inflammatory syndrome. Initial transthoracic echocardiography showed a normally functioning mitral prosthesis without evidence of vegetation. Given the persistent high clinical suspicion of infective endocarditis, transesophageal echocardiography was subsequently performed in accordance with the 2023 European Society of Cardiology guidelines and demonstrated a highly mobile vegetation measuring 11 × 4 mm attached to the atrial side of the prosthetic mitral valve. Cinefluoroscopy confirmed preserved prosthetic leaflet mobility without obstruction. Repeated blood cultures isolated multidrug-resistant Klebsiella pneumoniae susceptible only to colistin. Contrast-enhanced thoraco-abdomino-pelvic computed tomography revealed splenic infarction with bilateral perirenal fat stranding and mild ascites, consistent with systemic septic embolization, while brain magnetic resonance imaging showed no acute neurological complications. A diagnosis of definite early prosthetic mitral valve infective endocarditis complicated by splenic infarction was established. Despite initial colistin therapy, clinical and biological improvement was only achieved after escalation to rifampicin combined with imipenem/cilastatin, with complete disappearance of the vegetation on follow-up transesophageal echocardiography. This case highlights the pivotal role of multimodality imaging in diagnosing prosthetic valve endocarditis and detecting embolic complications, particularly in initially inconclusive transthoracic echocardiography, as well as the therapeutic challenges associated with prosthetic valve infective endocarditis caused by multidrug-resistant organisms.