Loss of Consciousness Caused by a Rare Etiology: Serratia Marcescens Endocarditis

Background: Serratia marcescens is an uncommon cause of infective endocarditis and is associated with a rapidly progressive clinical course, early embolic complications, and high mortality. Its initial presentation with neurological symptoms rather than cardiac manifestations is particularly rare and frequently contributes to diagnostic delay. Case Presentation: We report a 46-year-old male with multiple coagulation factor deficiencies undergoing intermittent hemodialysis via a subclavian catheter. Following non-sterile self-removal of his catheter, he presented to the emergency department with acute onset neck pain, altered mental status, and elevated inflammatory markers. Brain diffusion MRI revealed multiple lacunar infarcts initially attributed to minor cerebrovascular disease. Despite empiric broad-spectrum antimicrobial therapy, the patient’s neurological condition rapidly deteriorated. Blood cultures subsequently grew S. marcescens, and echocardiography performed on day 10 demonstrated a mitral valve vegetation consistent with infective endocarditis. Surgical intervention was deemed unsuitable due to the severity of clinical deterioration. The patient developed multiorgan failure and died on the 14th day of hospitalization. Discussion: This case highlights the aggressive nature of S. marcescens endocarditis, its strong association with catheter-related bloodstream infections, and its tendency to mimic primary neurological disease through early cerebral embolization. Biofilm-associated antimicrobial resistance likely contributed to treatment failure despite broad-spectrum therapy. Early integration of neurological findings, catheter history, and rising troponin levels is vital for timely diagnosis. Conclusion: S. marcescens endocarditis should be considered in patients presenting with unexplained altered mental status and a history of recent catheter manipulation. Prompt microbiological investigation and early echocardiographic assessment are essential for managing this high-mortality condition.