1. Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
2. Tuberculosis Research Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 33 North Drive, Building 33, Room 2W20D, Bethesda, MD 20892, USA.
3. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, W1144 Biomedical Science Tower, Pittsburgh, PA 15261, USA.