A Rare Presentation of Infective Endocarditis Due to Serratia marcescens

Serratia marcescens is an opportunistic organism that can commonly cause respiratory tract infections in immunocompromised individuals. It has also been shown to cause urinary tract infections and soft tissue infections. It has several virulence factors including fimbriae-like adhesions that allow for surface attachment and biofilm formation to increase the likelihood of infections in humans. However, it has rarely been shown to cause infective endocarditis but has an increased mortality compared to the usual microbial agents associated with it (Staphylococcus and Streptococcus). Therefore, a high index of suspicion is necessary to accurately diagnose and treat patients at risk. Most published cases of S. marcescens endocarditis show that almost all described patients had chronic medical conditions or cardiovascular abnormalities. Furthermore, treatment has become difficult as S. marcescens has been shown to exhibit antibacterial resistance with beta-lactamase production. Here, we present a complicated case of S. marcescens pneumonia and infective endocarditis with a good prognosis. Our patient had a rapid onset of complications (i.e. including joint infections, splenic abscesses, myositis, and septic arthritis), despite the initial benign presentation concerning for pneumonia. However, the patient had a favorable outcome due to the prompt work-up and treatment that was initiated. Therefore, S. marcescens bacteremia in a patient with risk factors should prompt further investigation with a thorough evaluation of source followed by immediate management. This case highlights the fastidious nature of S. marcescens. Further investigation needs to be done to elucidate the pathogenesis of the organism that can serve as a target for future therapeutic intervention.