Survival Strategies of Foodborne Pathogens and Commodity Contamination in Production Fields and Retail Outlets

Most of the major supermarkets in the United States crisp and mist fresh vegetables or at minimum mist vegetables in display cases. Crisping generally entails soaking of a commodity in water to rehydrate and misting is done on commodities while in display cabinets to limit wilting and improve appearance. During crisping product may become contaminated through exposure to contaminated equipment, workers, and other product. Misting of product may have unintended consequences if for example the lines delivering water develop biofilms harboring human pathogens. In the present study, formation of biofilms in mist water systems and its effect on microbial load of misted/crisped product is investigated. Experiments are also conducted to evaluate the efficacy of various sanitizers to reduce or eliminate cross-contamination during crisping. The shelf-life of crisped and misted product in retail and home setting is determined. Collectively, crisping and misting may contribute to improving product quality and shelf-life, but may also increase the likelihood of product and equipment contamination. Potential also exist for increase in harmful chemical by-products. The research will support the development of science based "best practices" to ensure that crisping, misting, or both do not adversely impact the microbial and chemical safety of fresh produce. Bacteria have the ability to adapt to varying environments which has facilitated their existence for millions/billions of years. From a practical food safety and shelf-life position recognizing and understanding how bacteria survive is essential. Studies conducted in the open-environment and in greenhouses suggests that enteric bacterial population of ≤104 CFU survive for short periods; not detectable on crops by culture or molecular methods. Companies conducting monitoring and test and hold programs indicate that enrichment of samples (water, soil, commodity) is required to detect pathogens of interest. Thus, it would seem that consumers suffer cases of foodborne illness from consuming produce that is apparently contaminated with extremely low levels of the causative agent. This may or may not be the case. Enteric foodborne pathogens may be at much greater levels but in dormant states that impede detection and facilitate contamination. In the present project, experiments that focus on ability of bacteria to undergo desiccation and entry in to a viable but-nonculturable state (VBNC) and subsequent contamination of or recovery on leafy greens is investigated. E. coli O157:H7 is exposed to water, soil, and chicken manure pellets and desiccated or VBNC state determined. Assessment of crop contamination and resuscitation on crops is investigated.