1. Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania.
2. National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa.
3. Department of Food Science and Technology, The University of Tennessee, Knoxville, Tennessee.
4. Dupont Experimental Station, Dupont Qualicon, Wilmington, Delaware.