Abstract Title: 
A Rare Case of Infective Endocarditis caused by Serratia marcescens

Background: 
Serratia marcescens is a gram-negative bacillus that usually causes respiratory and CNS infections but it rarely can cause infective endocarditis.

Case Presentation: 
A 62-year-old male with PMH of intravenous drug use and Hepatitis C presented to the ED with palpitations and back pain for three weeks with no reported fevers. In the ED, his vitals were: temperature 103.9° F, BP 105/72, HR 125, RR 20 and O2 saturation 100% on room air. The remainder of his examination revealed bilateral subconjunctival hemorrhages and multiple track marks; there were no neurological deficits, petechiae, or murmurs. Laboratory studies revealed WBC 12.82, bandemia of 13%, and lactic acid 4.1. An MRI brain revealed scattered acute infarcts; subsequent spinal MRIs were negative for abscesses. He was admitted for sepsis possibly secondary to endocarditis and started on broad spectrum antibiotics; an initial TTE was negative for vegetations, and blood cultures later grew S. marcescens. The patient subsequently developed an intermittent AV block. Repeat TTE revealed a linear echo-density on the aortic leaflets; TEE showed a 2cm vegetation on the aortic valve with perforation. He was transferred to a tertiary center for further care; he underwent aortic valve replacement, which was complicated by aortic root rupture. He also developed sick sinus syndrome and required a pacemaker. The remainder of his hospitalization was unremarkable and he was discharged on a prolonged antibiotic course.

Discussion: 
Infective endocarditis with S. marcescens is rare; some studies report only 0.14% of IE cases are caused by Serratia. Although IV drug users typically have higher rates of right-sided valvular endocarditis, S. marcescens tends to involve left-sided valves. S. marcescans is rapidly progressive. Typical symptoms include fever, myalgias, or dyspnea. Exam findings can include cardiac murmurs, splinter hemorrhages, Janeway lesions, Osler nodes, and Roth spots. IE diagnosis is made via positive blood cultures and vegetations on echocardiography. Surgical intervention is recommended within 7-10 days; mortality is as high as 85% in patients with Serratia who only received medical therapy. After prompt surgical intervention, antimicrobial treatment includes combination therapy of B-lactam and an aminoglycoside or fluroquinolone for at least six weeks. 


A Rare Case of Infective Endocarditis by Serratia Marcescens

Clinical Vignettes | Internal Medicine

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