Purpose: To determine the prevalence of foodborne pathogens, Salmonella and Shiga toxin-producing Escherichia coli (STEC), in produce from California diversified farms, and to quantify bacterial indicators of fecal contamination.
Methods: Three hundred sixty-seven leafy green and 305 tomato samples were collected from 17 diversified farms from 2015 to 2016. Generalized linear models were conducted to evaluate the association between E. coli prevalence and produce type, collection type, farm status, environment, irrigation water type, and period between manure application and harvest. The best model was selected based on Akaike’s information criterion.
Results: No sample was positive for Salmonella or E. coli O157:H7. One targeted spinach sample was positive for STEC O136. Random (11.6%; n=198) and targeted leafy greens (11.8%; n=169) were positive for generic E. coli (median=0 MPN/100 g, range 0 to 1.2×107 MPN/100 g). The prevalence of fecal coliforms in random and targeted leafy greens was 31.3% and 37.3%, respectively (median=0 MPN/100 g, range 0 to 1.4×108 MPN/100 g). For tomatoes, 4.9% of random samples (n=163) and 6.3% of targeted samples (n=142) were positive for generic E. coli (median=0 MPN/100g, range 0 to 4.6×105 MPN/100 g). Fecal coliforms were detected in 68.7% and 75.2% of tomato samples (median=1.2×103 MPN/100g, range 0 to 2.8×109 MPN/100 g). Noncertified organic samples had a higher probability of being E. coli positive. For total fecal coliforms, the best model included the use of surface water.
Significance: The prevalence of foodborne pathogens found in produce on diversified farms is low. Noncertified organic farm status and the use of surface water were identified as potential risk factors for fecal contamination of produce.