Methods: Retrospective cohort study of all Veteran patients with MRSA BSI who began therapy on vancomycin from 2007-2014. Patients were followed for 30 days. Potential predictors of switching measured at the time of admission included demographics, diagnoses, and comorbidities. Co-infections were defined using ICD-9 codes. Additional predictors were time-varying during index admission, including: therapeutic level of vancomycin (defined as 24-hour area under concentration-time-curve to minimum inhibitory concentration [AUC/MIC]>=400), lab values, and acute kidney injury (AKI, defined by change in creatinine). A Cox proportional hazards model was used to evaluate the association between predictors and the relative hazards of switching to daptomycin or linezolid.
Results: 17,841 patients had MRSA BSI and were given vancomycin initially. By 30 days, 18% of patients were therapeutically switched including 9.4% (n=1,680) to daptomycin and 10.5% (n=1,873) to linezolid. 4,763 (27%) patients had a therapeutic vancomycin dose within 5 days of initiating vancomycin, 1,318 (7%) had a subtherapeutic dose, and 11,760 (66%) could not have an AUC calculated. 5,692 (31.9%) patients experienced AKI after initiating vancomycin. Factors associated with increased likelihood of switching included subtherapeutic vancomycin dose (hazard ratio [HR]=1.53; 95% confidence interval [CI]: 1.29, 1.82); AKI (HR=1.51; 95%CI: 1.34, 1.70); co-infections with osteomyelitis (HR=1.28; 95%CI: 1.13, 1.46), pneumonia (HR=1.35; 95%CI: 1.10, 1.66) and endovascular infections (HR=1.18; 95%CI: 1.05, 1.32).
Conclusion: A high proportion of patients with MRSA bacteremia were therapeutically switched. Patients with co-infections may be targets for early daptomycin/linezolid therapy. Efforts should continue towards improving vancomycin dosing during the first 5 days of therapy.
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M. Vaughan Sarrazin, None
M. Jones, None
D. Livorsi, None
R. Nair, None
M. Goto, None
B. Alexander, None
B. Beck, None
E. Perencevich, None
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