1. Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Bldg 5 B/12 G-11, Centers for Disease Control and Prevention, Public Health Service, US Department of Health and Human Services, 1600 Clifton Rd, Atlanta, GA 30333, USA
2. Department of Biology, Clark-Atlanta University, Atlanta, GA, USA
3. Department of Genetics, University of Georgia, Athens, GA, USA