Microbial Food Safety of Fresh Produce: Pathogen Survival in Soil, Water, and On Fresh Produce.

Ongoing research at the University of Maryland Eastern Shore (UMES) in collaboration with USDA-ARS, Beltsville, MD focuses on addressing avenues leading to fresh produce contamination with pathogenic microorganisms such as E. coli 0157:H7, Salmonella, and Staphylococcus. Irrigation water, manure application, runoff water, and bioaerosols/dust particles generated from farm operations are potential avenues leading to fresh produce contamination.  Our main objective is to minimize microbial contamination of fresh produce at the farm level.  Our studies revealed no viable E. coli or Salmonella were detectable in dry poultry litter (8-17% moisture content) although Staphylococcus aureus was abundant (6.8-7.8 log10 cfu/gdw). Staphylococcus was transported >120m downwind from the litter-handling site; therefore, Staphylococcus could be used as a marker in microbial bioaerosol dissemination and transport studies. Our rain simulation and runoff studies, where soils were amended with poultry litter, poultry compost, and dairy and swine manure, showed that poultry litter enhanced growth of bacteria more than any other manure.  Similar findings were found in our field studies where soil was amended with various types of manure and inoculated with non-pathogenic strains of generic E. coli and attenuated E. coli 0157:H7.  An irrigation study where field-grown tomatoes were inoculated 10 days before harvest with bovine manure examined the persistence of generic E. coli and total coliforms; bacterial populations fluctuated in response to weather events within the 10-day sampling period. Several studies in these topic areas are also being conducted to gain quantitative insights about pathogen survival and persistence in field production of fresh produce.