1. Department of Microbiology, 226 Nash Hall, Oregon State University, Corvallis, OR 97331, USA
2. Department of Internal Medicine, 5323 Harry Hines Blvd., University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
3. Department of Microbiology, 5323 Harry Hines Blvd., University of Texas Southwestern Medical Center, Dallas, TX 75390, USA