Assessing clinical outcomes of vancomycin treatment in adult patients with penicillin-resistant Enterococcus faecium bacteremia

Enterococcal bacteremia is associated with high mortality and long-term hospitalization. Here, we aimed to investigate the clinical outcomes and evaluate risk factors for mortality in adult patients treated with vancomycin (VCM) for penicillin-resistant Enterococcus faecium (E. faecium) bacteremia. Data were collected from inpatients at a single university hospital between January 2009 and December 2020. The area under the curve (AUC) of VCM was calculated using the Bayesian approach. The primary outcome was 30-day in-hospital mortality. Univariate analysis showed significant differences in the combined use of vasopressors, history of the use of inactive antimicrobial agents against E. faecium, VCM plasma trough concentration, and renal dysfunction during VCM administration between 30-day mortality and survival groups. However, the AUC/minimum inhibitory concentration (MIC) was not significantly different. Multivariate analysis revealed that concomitant vasopressors were an independent risk factor for 30-day all-cause mortality (odds risk, 7.81; 95% confidence interval, 1.16-52.9; P = 0.035). VCM plasma trough concentrations and AUC/MIC in the mortality group were higher than those in the surviving group. Depending on the drug-susceptibility results of E. faecium, it is considered that the AUC/MIC is calculated at a double AUC value. No association between AUC/MIC and treatment effect in E. faecium bacteremia was assumed because the known target AUC/MIC was sufficiently achieved in the mortality group. When an immunocompromised host develops E. faecium bacteremia with septic shock, especially in situations where the hemodynamics of using a pressor agent is unstable, treating it exclusively by sufficient exposure to antibacterial agents may be difficult.