697 - 8 Years of Characteristics and Outcomes of Patients with MRSA Endocarditis Based on Vancomycin Minimum Inhibitory Concentration: Experience at a Tertiary Care Hospital

Background: Vancomycin has been the mainstay of treatment for methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE). MRSA reduced susceptibility to vancomycin is a growing threat. Data assessing the effect of vancomycin reduced susceptibility on outcomes is limited. Our study aimed to evaluate characteristics and outcomes of MRSA-related IE based on the minimum inhibitory concentration (MIC) to vancomycinCharacteristics and outcomes of 51 patients with MRSA-related endocarditis according to the minimal inhibitory concentration (MIC) to vancomycin


Methods: IRB approval was obtained for a retrospective cohort study at a tertiary care center. Records of hospitalized adults diagnose with IE by ICD-9/ICD-10 CM codes were identified from 2011 to 2018. 51 patients had MRSA-related IE and were selected for the analysis. Demographic, microbiologic, Imaging and outcome variables were obtained. Characteristics and outcomes of patients with MRSA-related IE according to the MIC to vancomycin (≤ vs. > 1 mcg/mL) were compared

Results: 35.3% of patients had a MIC > 1 mcg/mL. 59% were men, mean age was 46±3 years old.  65% acquired the infection through injection drug use. Only 3.9% of patients had prosthetic valve IE. 35.3% had tricuspid valve vegetation, 25.5% mitral valve and 21.6% aortic valve vegetation. Two patients had IE possibly related to a PICC-line infection; both of these patients had a MIC to vancomycin >1 mcg/mL, suggestive of prolonged antibiotic therapy. All patients with MRSA-related IE were started empirically on vancomycin. Patients with a MIC > 1 mcg/mL were more likely to be switched to a combination of daptomycin and ceftaroline, compared to those with a MIC ≤ 1 mcg/mL (44.4% vs. 6.1%; P=0.001). 25.4% underwent valvular replacement within 6 months. 12% died within 90 days. MRSA-related IE with MIC > 1mcg/mL did not confer and an increase risk in in-hospital mortality (11.1% vs. 15.2%; P=0.67) or mortality at 90 days (11.1% vs. 12.5%; P=0.89).

Conclusion: In this single-center experience, we found that in 8 years 35% of patients with MRSA-related IE had MIC  >1 mcg/mL. This is an alarming finding. Although our study did not reach statistic significance we didn't found difference in valvular surgery requirement or mortality among those with MIC > 1mcg/d as compared to those with a more sensitive MRSA strain. A study with more power or a metha-analysis will be require to better answer this question.