1. Department of Microbiology, Franklin College of Arts and Sciences, The University of Georgia, Athens, Georgia 30602, USA;
2. The Belle W. Baruch Institute of Coastal Ecology and Forest Science, P. O. Box 596, Georgetown, South Carolina 29442, USA;
3. Food and Drug Administration, Center for Veterinary Medicine, Office of New Animal Drug Evaluation, 7500 Standish Place, HVF-102, Rockville, Maryland 20855, USA;
4. Department of Comparative Medicine, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, Tennessee 37996-4500, USA;