Purpose: To study the movement of indicator (fecal coliforms, E. coli, and Enterococcus sp.) and pathogenic (Salmonella, and non-O157:H7 STEC) organisms at the animal-produce interface.
Methods: Between the months of March - December 2014, 770 samples comprising of manure, various vegetable crops, soil, air, and water were collected from two independently managed farming systems rearing Dairy or Poultry next to vegetable fields. Samples were collected from the animal source and at 30, 200, and 400 feet away from animal enclosures. The population of indicator microorganisms and the presence of Salmonella and non-O157:H7 STEC was determined from all sample sources and confirmed via probe-based PCR.
Results: STEC organisms were consistently isolated from produce in close proximity to dairy (30%) and poultry (24%) enclosures irrespective of setback distance. No Salmonella was isolated from produce within a 400-foot setback distance from dairy or poultry operations. Salmonella was only isolated from one (soil) out of 770 samples. Average populations of E. coli, coliforms, and Enterococci from all produce samples were 2.01, 3.33, and 2.58 log CFU/g, respectively. Significantly higher populations of these microorganisms were isolated during the summer months (P < 0.05). No significant differences in the population of indicator microorganisms were observed at varying setback distances from the selected animal enclosures (P < 0.05).
Significance: Consistent levels of STEC and indicator microorganisms were isolated from produce and other matrixes within a 400-foot setback distance from various animal operations. These findings suggest that new metrics for buffer setbacks within diversified farming systems should be assessed to improve fresh produce safety.