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P1-18 Salmonella Transport through Irrigation Systems and the Risk of Fresh Produce Contamination on Farms in Southern Georgia

Monday, August 1, 2016
America's Center - St. Louis
Debbie Lee, Emory University, Atlanta, GA
Moukaram Tertuliano, University of Georgia, Tifton, GA
George Vellidis, University of Georgia, Tifton, GA
Elizabeth Antaki, University of California, Davis, Davis, CA
Casey Harris, University of Georgia, Tifton, GA
Michele Jay-Russell, University of California-Davis, Davis, CA
Karen Levy, Emory University, Atlanta, GA
Introduction: Fresh produce can become contaminated through numerous pathways from farm to fork. Contaminated irrigation water has been cited as a source of outbreaks linked to fresh produce. Surface water ponds are used for irrigation on many farms in southern Georgia even though Salmonella has regularly been detected in surface water in the region in low concentrations. Salmonella can survive in non-host environments, which potentially poses a hazard to produce safety.

Purpose: The purpose of this study was to evaluate the prevalence of Salmonella in surface water ponds, irrigation systems, and on fresh produce crops at harvest on farms in southern Georgia, in order to assess the risk for pre-harvest contamination of produce irrigated with surface water. 

Methods: Ninety-four water samples (2 L) from irrigation sources (surface water ponds and wells) and associated distribution systems (drip irrigation, sprinkler, and pivot), and 65 standardized units of produce were collected. Salmonella concentrations were enumerated using a most probable number (MPN) method. Presumptive positives were confirmed using PCR and isolates were analyzed with pulsed-field gel electrophoresis (PFGE). 

Results: Salmonella was detected in 29% of irrigation ponds and systems throughout the study, with positive samples ranging in concentration from 0.055 MPN/100 ml to 1.8 MPN/100 ml. Two out of 65 produce samples (cantaloupe and cucumber) were positive for Salmonella, but concentrations were low (1.1 MPN/sample). PFGE analysis indicated 26 distinct pulsotypes present in the samples and that strains found in irrigation ponds were also found in irrigation systems. Strains found on crops were also detected in the irrigation systems, indicating that Salmonella in water from irrigation systems could be a source of contamination of produce. 

Significance: This study has shown that pre-harvest contamination of produce with Salmonella occurs on farms that irrigate with surface water contaminated with Salmonella.

Back to: Poster Session 1 – Produce, Meat, Poultry and Eggs, Non-microbial Food Safety; Laboratory and Detection Methods; Communication Outreach and Education; Seafood; Antimicrobials; Food Toxicology
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