A Rare Case of Serratia marcescens Causing Mycotic Aneurysm and Septic Emboli in Intravenous Drug User

There are few literatures highlighting the presence of a mycotic aneurysm in the setting of bloodstream infection by Serratia. A 33-year-old male with a history of Marfan syndrome, mitral valve prolapse, and intravenous drug use (IVDU) presented to the ED with fever, nausea, and non-bloody emesis, and vague abdominal pain with concern for sepsis. With the strong association between IVDU and infective endocarditis, transthoracic and transesophageal echocardiograms were performed and were negative for vegetations. Abdominal CT and positron emission tomography (PET) scan were performed and revealed thrombosis at the first jejunal branch of the superior mesenteric artery (SMA), left renal pole infarct, and superior splenic pole infarct. Following CT angiography for potential thrombolysis, aneurysmal formation was discovered proximal to the filling defect within mid-SMA. Blood cultures drawn at presentation grew Serratia marcescens. The patient was treated with appropriate antibiotic, and recommended indefinite anticoagulation. The patient was then recommended to follow up with vascular surgery within two weeks for repeat abdominal CT angiogram.