Summary of Awards to Date

Persistence and detection of norovirus, Salmonella, and pathogenic Escherichia coli on basil and leafy greens.


Dec. 1, 2009 - Nov. 30, 2012

Funding Agency

Center for Produce Safety & BARD

Amount Awarded



Dallas Hoover, Ph.D.
University of Delaware


K. Kniel-Tolbert, J. Patel, M. Sharma


The questions addressed in this proposal are applicable to major priority area 2 of the CPSBARD program: Survival and growth requirements for human pathogens on produce, as well as minor priority area 4: Definition of human pathogen reservoirs and vectors and quantification of transference. In the U.S. it is estimated that there are approximately three million cases a year of illness caused by fecally contaminated fruits and vegetables; in Israel at least 20% of foodborne illnesses are attributed to fruits and vegetables. Noroviruses, Salmonella and pathogenic Escherichia coli are the three main groups of enteric pathogens associated with fresh produce and selected for study by the three participating laboratories. The overall objective of this study is to assess the persistence and transfer of norovirus, Salmonella, Escherichia coli O157:H7 and avian pathogenic E. col (APEC) on leafy greens (lettuce and spinach) and basil, to gain information to better enhance the safety of produce and reduce transmission of these pathogens in the field. Technion‐Israel will use basil and spinach to examine persistence and mechanisms of attachment of Salmonella employing mutant strains for study of factors affecting attachment to foliar surfaces. The University of Delaware and USDA‐EMFSL in Beltsville will evaluate lettuce, spinach and basil in their studies of norovirus and bacteria; the University of Delaware will investigate persistence of noroviruses, APEC and nonpathogenic E. coli on plant surfaces in a comparison study using spot inoculation, while USDA‐EMFSL will evaluate E. coli O157:H7, APEC, nonpathogenic E. coli, and Salmonella simulating field conditions using lower, more realistic population levels and different irrigation regimes. Methodology will include enumerating of pathogens by culture methods and RT‐PCR and localization by microscopy. USDA‐EMFSL and the University of Delaware will share detection and enumeration protocols for the shared varieties of E. coli under study. In addition to RT‐PCR, norovirus will also be quantified by plaque assay. Completion of the project incorporating three different plant environments from the three laboratories will generate information that better characterizes and predicts the survival and transmission of these pathogens at more realistic levels of contamination in plants in the field.