Polymicrobial infective endocarditis in the setting of intravenous drug use

Abstract

Abstract Background: The pathogenesis of infective endocarditis (IE) involves the interaction of microorganisms such as bacteria or fungi with the endothelial lining of heart valves. Patients with IE typically have a pre-existing valvular defect that allows highly virulent organisms to attach to valve leaflets. In patients with a history of intravenous drug use (IVDU), a leaflet of the tricuspid valve is typically involved in the setting of bacteremia or fungemia as the right heart is the site of venous return. Recent data shows that 80-90% of IE cases are caused by microorganisms such as staphylococci or streptococci, but the isolation of more than one microorganism is only seen in around 1-6.8% of cases. Case presentation: This is a 31-year-old Caucasian male with a past medical history of tobacco use, IVDU, major depressive disorder, generalized anxiety disorder, and chronic left lower extremity wound presenting to the emergency department (ED) with shortness of breath. Upon further investigation, patient was found to have polymicrobial IE growing both methicillin-sensitive staphylococcus aureus (MSSA) as well as group A streptococcus (GAS) pyogenes. He was diagnosed on transthoracic echo with pulmonary emboli seen on CT imaging. Patient received IV cefazolin where he was monitored on the medical floors for several weeks. Conclusions: This case report is meant to highlight the importance of assessing for polymicrobial IE in patients at risk. Given the possible uncommon pathology behind a patient’s symptoms with different microorganisms, it is imperative to identify causative organisms early to administer proper therapeutic treatment. Using clinical judgment to repeat investigations when warranted in order to properly diagnose patients is important when clinical suspicion for disease is high. Understanding the variations of severity/treatment between monomicrobial versus polymicrobial IE can drastically change prognosis. Finally, acknowledging the difficulty of lengthy in-patient hospital therapies in patients unable/unwilling to stay is important in this patient population.