P3-51 Low Prevalence of Foodborne Pathogens Found in Produce Grown on Diversified Farms in California

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Nora Navarro-Gonzalez , University of California-Davis, Western Center for Food Safety , Davis , CA
Laura Patterson , University of California-Davis, Department of Population Health & Reproduction , Davis , CA
Peiman Aminabadi , Western Center for Food Safety, University of California , Davis , CA
Alda Pires , Department of Population Health and Reproduction, School of Veterinary Medicine, University of California , Davis , CA
Shirley Micallef , University of Maryland , College Park , MD
Robert Buchanan , University of Maryland, Department of Nutrition and Food Science and Center for Food Safety and Security Systems , College Park , MD
Michele Jay-Russell , Western Center for Food Safety, University of California , Davis , CA
Introduction: Diversified farms raise a wide range of animal and plant varieties, and are usually small to medium-sized with direct sales to consumers. Their popularity and importance is increasing, but practices associated with this type of farming system may pose a risk for food safety.

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.