Clinical Outcomes in Patients with Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Bloodstream Infection
The prevalence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) infections varies in the literature, complicated by the lack of routine screening procedures; however, limited data suggest hVISA has been associated with persistent bloodstream infections (BSI) and vancomycin failure yet these studies have been confounded by design. We conducted this study to characterize patients with BSI caused by hVISA compared to vancomycin-susceptible Staphylococcus aureus (VSSA) treated with vancomycin. This retrospective, multi-center matched (1:1) cohort study compared the clinical characteristics and outcomes of hVISA and VSSA. Patients with hVISA methicillin-resistant Staphylococcus aureus (MRSA) BSI from 2004-2012 were matched to VSSA-MRSA BSI. The primary outcome was vancomycin failure, defined as a composite of: persistent bacteremia (≥ 7 days), persistent signs and symptoms, change of MRSA antibiotic, recurrent BSI, or MRSA-related mortality. We identified 122 matched cases. Overall vancomycin failure was 57%; 82% hVISA vs. 33% VSSA, (p < 0.001). Individual components of failure in hVISA vs. VSSA: persistent bacteremia: 59% vs. 21%, (p < 0.001); MRSA therapy changed: 54% vs. 25%, (p = 0.001); MRSA-related mortality: 21% vs. 10%, (p = 0.081), recurrence of BSI: 26% vs. 2%, (p < 0.001). Using logistic regression analysis and adjusting for covariates, hVISA (aOR, 11.1; 95% CI 4.3-28.7) and ICU admission (aOR, 4.5; 95% CI 1.8-11.6) were still independently associated with vancomycin failure. Relative to VSSA BSI, patients with hVISA were more likely to experience failure to vancomycin, including persistent bacteremia and recurrence. Our results indicate that hVISA was responsible for considerable morbidity.
Casapao, A. M., Leonard, S. N., Davis, S. L., Lodise, T. P., Patel, N., Goff, D. A., LaPlante, K. L., Potoski, B. A., … Rybak, M. J. (2013). Clinical Outcomes in Patients with Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Bloodstream Infection. Antimicrobial agents and chemotherapy, 57(9), 4252-4259. doi: 10.1128/AAC.00380-13