1. Center for Food Safety and Nutrition (CFSAN), Department of Health and Human Services, Food and Drug Administration, Office of Applied Research and Safety Assessment (OARSA), Division of Virulence Assessment, Laurel, MD 20708, USA
2. Institute of Clinical Research, University of Zulia, Maracaibo 4001-A, Venezuela
3. Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA