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P3-137 Incidence and Persistence of Salmonella and Escherichia coli in Environmental Samples from North Carolina Tomato Production Systems

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Diane Ducharme, North Carolina State University, Kannapolis, NC
Christopher Gunter, North Carolina State University, Raleigh, NC
Lee-Ann Jaykus, North Carolina State University, Raleigh, NC
Penelope Perkins-Veazie, North Carolina State University, Kannapolis, NC
Otto Simmons, North Carolina State University, Raleigh, NC
Eric Brown, U.S. Food and Drug Administration, College Park, MD
Jie Zheng, U.S. Food and Drug Administration, College Park, MD
Erik Burrows, U.S. Food and Drug Administration, College Park, MD
Charles Wang, U.S. Food and Drug Administration, College Park, MD
Gabriela Caroline Arce, U.S. Food and Drug Administration, College Park, MD
Tim Muruvanda, U.S. Food and Drug Administration, College Park, MD
Rebecca Bell, U.S. Food and Drug Administration, College Park, MD
Introduction: An increasing number of foodborne outbreaks involving Salmonella and Escherichia coli 0157:H7 are linked to fresh-market tomatoes. Recently proposed Food Safety Modernization Act (FSMA) rules suggest the use of generic E. coli as an indicator for pathogens in agricultural waters.  Previous studies indicate Salmonella withstanding a greater range of environmental stresses and thereby demonstrate its capacity to survive and persist in the environment.

Purpose: The purpose of this study is to identify specific environmental niches for Salmonella and correlate Salmonella presence with generic E. coli concentrations in environmental waters within tomato field production systems. 

Methods: Environmental samples were collected during the NC tomato production season from 3 farm locations. Water samples (49) collected during August – November were enumerated for generic E. coli using the IDEXX Colilert and quanti-tray 2000 system, with concentrations expressed as MPN/100 ml.  Corresponding tomato (fruit, blossom, leaf), weeds, soil, water, fecal material samples (469) were analyzed for the presence of Salmonella by enrichment using a modified BAM cultural method as well as by real-time PCR.  

Results: Salmonella was isolated from the July (twenty), August (twenty-six) and September (nine) sampling periods; 49% (27/55) of these isolates were from water,  42% (23/55) from stream sediment, 5% (3/55) were isolated from inside tomatoes, and 4% (2/55) were isolated from the surface of tomatoes.   Using parameters for generic E. coli from the currently proposed FSMA rules for agricultural waters, 16% (8/49) of the water samples met the single sample action level of 235 CFU/100 ml, indicating fecally contaminated water sources that may require mitigation.

Significance: This work will lead to a better understanding of environmental reservoirs, persistence and movement of Salmonella, as well as correlations between proposed indicator species and pathogens.  Information gained through this research can assist in management of tomato on-farm production systems with ultimate influences on human illnesses.

Back to: Poster Session 3 - Applied Laboratory Methods, Novel Laboratory Methods, Produce, Risk Assessment
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