Biological Control Strategies Targeted Against Human Pathogens On Sprouts

Biological control strategies targeted against human pathogens on sprouts

2005 IFT Annual Meeting, July 15-20 – New Orleans, Louisiana

Session 62, Intervention strategies for fresh produce
W. F. FETT, Food Safety Intervention Technologies Research Unit, USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598

Foodborne outbreaks due to consumption of raw or lightly cooked alfalfa and other types of sprouts contaminated with bacterial human pathogens are a food safety concern worldwide. Sprout-related outbreaks have occurred in the U.S. each year from 1995 to 2004. Outbreaks were due to the presence of Salmonella enterica or Escherichia coli O157:H7 on alfalfa, clover and mung bean sprouts. Epidemiological evidence as well as bacteriological studies indicates that the primary source of the human pathogens is the sprouting seed. There are numerous published studies on the use of chemical and physical methods for sanitizing sprouting seed and the efficacy of these interventions compared to the U.S. Food and Drug Administration recommended seed treatment (20,000 ppm of free chlorine) will be briefly discussed. No single chemical or physical intervention has been reported to eliminate bacterial pathogens from artificially inoculated sprouting alfalfa seed while maintaining acceptable seed germination and sprout yield. In contrast, there are few studies on the use of biological control methods for inhibiting the outgrowth of bacterial human pathogens on seed during the sprouting process. The antagonistic activity of plant-associated bacteria towards S. enterica and E. coli O157:H7 both in vitro and in situ using sprouting alfalfa seed as the model system was studied. One plant-associated bacterium (a fluorescent pseudomonad) was identified that is inhibitory towards both pathogens. The mode of action responsible for antibiosis is currently being studied and the results will be presented. The application of bacterial antagonists to sprouting seed and to sprouts after harvest for the purpose of inhibiting the growth and survival of bacterial human pathogens may be useful food safety interventions for both conventional and organic sprout growers. Biological control strategies may also be applicable for controlling the growth and survival of human pathogens on fresh-cut produce.