Infective Endocarditis Caused by Serratia marcescens: A Case Report and Literature Review

<i>Serratia (S.) marcescens</i> is an opportunistic, gram-negative pathogen most commonly associated with respiratory tract, urinary tract, and soft-tissue infections. Reports of <i>S. marcescens</i> as a causative agent of infective endocarditis are rare, especially when compared with the more frequently implicated pathogens such as <i>Staphylococcus</i> and <i>Streptococcus</i> species. The clinical presentation, diagnostic challenges, and therapeutic considerations of <i>S. marcescens</i> endocarditis remain poorly characterized in the literature. This case report aims to provide a detailed description of an unusual presentation of <i>S. marcescens</i> infective endocarditis and to review previously reported cases to highlight common features, treatment strategies, and outcomes. We report the case of a middle-aged male with a significant past medical history of atrial fibrillation managed with warfarin and mitral valve replacement for rheumatic mitral stenosis. The patient was initially admitted under the neurosurgery service with bilateral subdural hematomas and underwent a right-sided mini-craniotomy with evacuation and subdural drain insertion. Three weeks postoperatively, he developed hypotension and fever. Blood cultures grew <i>S. marcescens</i>, and transesophageal echocardiography (TEE) revealed a 7 × 3 mm vegetation on the prosthetic mitral valve. The patient was treated with a combination of intravenous meropenem and gentamicin for a total of four weeks. Follow-up TEE demonstrated complete resolution of the vegetation, and the patient had an uneventful recovery.