Assistant Professor University of Virginia School of Medicine University of Virginia Charlottesville, Virginia, United States
Background: Excess antibiotic exposure, particularly broad-spectrum, is associated with significant morbidity in very low birth weight (VLBW) infants. An antibiotic spectrum index (ASI, points assigned per drug based on spectrum) calculated per antibiotic day (AD, calendar days with any number of antibiotic drugs or doses) was developed as a more detailed way to compare antibiotic exposure than days of therapy (DOT, calendar days per drug).
Objective: We sought to compare ASI across multiple NICUs and to evaluate drivers of differences.
Design/Methods: We extracted data from NICU patients for two years at the University of Virginia (UVA) and St. Louis Children’s Hospital (SLCH) and one year at Columbia University Medical Center (CUMC). We calculated the ASI per AD for all admitted VLBW infants <32 weeks gestational age (GA). Clinical variables were compared as percent or days per 1,000 patient-days (PD). We used one-way ANOVA to compare patient-level variables across the three sites.
Results: We identified 2067 exposures to antibiotics for 734 VLBW infants <32w GA. Table 1 compares patient characteristics across the three NICUs. GA, birth weight, and sex were similar among the sites. Mortality and infection rates were highest at SLCH, the site with the highest ASI/AD. UVA had the highest DOT/1000 PD yet the lowest ASI/AD, in part due to the high usage of UTI prophylaxis, but remained lower with UTI prophylaxis excluded. CU had notably low ventilator days and lower infection rates with the lowest DOT/1000 PD and an ASI/AD value similar to SLCH and higher than UVA. Most of the positive blood cultures grew CONS (Figure 1). Antibiotic utilization varied by site (Figure 2). Despite differences in MRSA screening and colonization rates, vancomycin usage was similar between centers. Conclusion(s): The ASI proved to be a useful metric for comparing antibiotic use in three NICUs with differences in patient characteristics. The NICU with the highest DOT had the lowest ASI per AD, driven by empiric antibiotic choices. The NICU with the highest antibiotic use and spectrum metrics had the highest mortality and infection rates.
Table 1. Patient characteristics and antibiotic metrics by site. *p < 0.05 by one-way ANOVA; † only outborn infants are screened for MRSA at UVA. SLCH and CU screen all infants on admission and CU repeats screening during the admission.
Figure 1. Frequency of organisms isolated in positive blood cultures, grouped by site.
Figure 2. Days of therapy (DOT) per 1,000 patient-days (PD) for each antimicrobial drug or drug class, grouped by site.
Authors/Institutions: Brynne A. Sullivan, University of Virginia School of Medicine, Charlottesville, Virginia, United States; Aaron W. Wallman-Stokes, University of Vermont Medical Center, Burlington, Vermont, United States; Federica Picozzi, Columbia University Irving Medical Center, New York, New York, United States; Rakesh Sahni, Columbia University Irving Medical Center, New York, New York, United States; Karen Fairchild, University of Virginia School of Medicine, Charlottesville, Virginia, United States; Jason Newland, Washington University in St. Louis, St. Louis, Missouri, United States; Christopher C. McPherson, Washington University School of Medicine, St. Louis, Missouri, United States; Zachary A. Vesoulis, Washington University in St Louis School of Medicine, St. Louis, Missouri, United States