1. Department of Medicine, Section of Infectious Diseases, Baylor College of Medicine, Houston, TX, USA;
2. Section of Infectious Diseases, Atlanta VA Medical Center, Atlanta, GA, USA;
3. Division of Infectious Diseases, Emory University School of Medicine, Atlanta, GA, USA;
4. Section of Infectious Diseases, Medical Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX, USA