1. Department of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
2. Department of Biostatistics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
3. Division of Pharmaceutical Outcomes and Policy, University of North Carolina School of Pharmacy , Chapel Hill, North Carolina , USA
4. Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
5. Clinical Microbiology Laboratory, University of North Carolina Hospitals , Chapel Hill, North Carolina , USA