Antistaphylococcal β-Lactams versus Vancomycin for Treatment of Infective Endocarditis Due to Methicillin-Susceptible Coagulase-Negative Staphylococci: a Prospective Cohort Study from the International Collaboration on Endocarditis

The phenotypic expression of methicillin resistance among coagulase-negative staphylococci (CoNS) is heterogeneous regardless of the presence of the mecA gene. The potential discordance between phenotypic and genotypic results has led to the use of vancomycin for the treatment of CoNS infective endocarditis (IE) regardless of methicillin MIC values. In this study, we assessed the outcome of methicillin-susceptible CoNS IE among patients treated with antistaphylococcal beta-lactams (ASB) versus vancomycin (VAN) in a multicenter cohort study based on data from the International Collaboration on Endocarditis (ICE) Prospective Cohort Study (PCS) and the ICE-Plus databases. The ICE-PCS database contains prospective data on 5,568 patients with IE collected between 2000 and 2006, while the ICE-Plus database contains prospective data on 2,019 patients with IE collected between 2008 and 2012. The primary endpoint was in-hospital mortality. Secondary endpoints were 6-month mortality and survival time. Of the 7,587 patients in the two databases, there were 280 patients with methicillin-susceptible CoNS IE. Detailed treatment and outcome data were available for 180 patients. Eighty-eight patients received ASB, while 36 were treated with VAN. In-hospital mortality (19.3% versus 11.1%; P = 0.27), 6-month mortality (31.6% versus 25.9%; P = 0.58), and survival time after discharge (P = 0.26) did not significantly differ between the two cohorts. Cox regression analysis did not show any significant association between ASB use and the survival time (hazard ratio, 1.7; P = 0.22); this result was not affected by adjustment for confounders. This study provides no evidence for a difference in outcome with the use of VAN versus ASB for methicillin-susceptible CoNS IE.