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Effect of Vancomycin Minimal Inhibitory Concentration on the Outcome of Methicillin-Susceptible Staphylococcus aureus Endocarditis.
Clin Infect Dis. 2014 Mar 18;
Authors: Cervera C, Castañeda X, de la Maria CG, Del Rio A, Moreno A, Soy D, Pericas JM, Falces C, Armero Y, Almela M, Ninot S, Pare JC, Mestres CA, Gatell JM, Marco F, Miro JM, the Hospital Clinic Endocarditis Study Group
Abstract
Background. Staphylococcus aureus endocarditis has a high mortality rate. Vancomycin minimum inhibitory concentration (MIC) has been shown to affect the outcome of methicillin-resistant S. aureus (MRSA) bacteremia, and recent data point to a similar effect on MSSA bacteremia. We aimed to evaluate the effect of vancomycin MIC on left-sided S. aureus infective endocarditis (IE) treated with cloxacillin. Methods. We analyzed a prospectively collected cohort of patients with IE in a single tertiary-care hospital. Vancomycin, daptomycin, and cloxacillin MIC was determined by E-test. S. aureus strains were categorized as low vancomycin MIC (< 1.5 µg/mL) and high vancomycin MIC (≥ 1.5 µg/mL). The primary endpoint was in-hospital mortality. Results. We analyzed 93 patients with left-sided IE treated with cloxacillin, of whom 53 (57%) had a vancomycin MIC<1.5 µg/mL and 40 (43%) a vancomycin MIC≥1.5 µg/mL. In-hospital mortality was 30% (16/53) in patients with a low vancomycin MIC and 53% (21/40) in those with a high vancomycin MIC (p=0.030). No correlation was found between oxacillin MIC and vancomycin or daptomycin MIC. Logistic regression analysis showed that higher vancomycin MIC increased in-hospital mortality 3-fold (OR 3.1, 95% CI 1.2-8.2) after adjustment for age, year of diagnosis, septic complications, and non-septic complicated endocarditis. Conclusion. Our results indicate that vancomycin MIC could be used to identify a subgroup of patients with methicillin-susceptible S. aureus IE at risk of higher mortality. The worse outcome of staphylococcal infections with a higher vancomycin MIC cannot be explained solely by suboptimal pharmacokinetics of antibiotics.
PMID: 24647021 [PubMed - as supplied by publisher]