Abstract
PURPOSE: This study aimed to compare mortality and outcomes among patients with injection drug use (IDU)-associated infective endocarditis (IE) caused by MRSA (methicillin-resistant Staphylococcus aureus) versus MSSA (methicillin-susceptible Staphylococcus aureus). PATIENTS AND METHODS: A single-center retrospective cohort study was performed on adult patients (≥18 years old) at a large academic medical center in the Mid-Southern United States of America between January 2013 and January 2020 to compare the mortality and outcomes of initial cases of IDU-associated IE due to MRSA and MSSA. All cases were confirmed using the Duke criteria for IE. RESULTS: A total of 175 IE patients were divided into two groups based on the causative agent: MRSA and MSSA. A total of 25 patients (14.3%) died during the index hospitalization, while 34 (19.4%) died within one year of index hospitalization. We observed no statistically significant differences between MRSA IE and MSSA IE in terms of mortality, intensive care unit admissions, hospital readmission rates, IE recurrence, or surgical intervention. The major difference between the two groups was the significantly higher rate of septic pulmonary emboli in the MRSA IE group than in the MSSA IE group (p = 0.0012). This was supported by the increased rate of tricuspid valve vegetation in MRSA IE patients (72.7%). CONCLUSION: Our study affirms the overall severity and high mortality rate of Staphylococcus aureus IE, independent of methicillin resistance status, even in the presence of appropriate antimicrobial therapy. With the increasing prevalence of IE caused by MRSA and MSSA, these challenging infections will continue to require aggressive intervention and treatment.