Start | Browse by Day | Author Index | Personal Scheduler

P3-138 A Microbiological Survey of Small- and Medium-Sized Tomato Farms in Maryland, Delaware and New Jersey

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Sivaranjani Pagadala, University of Maryland-College Park, College Park, MD
Sasha Marine, University of Maryland, Salisbury, MD
Shirley Micallef, University of Maryland-College Park, College Park, MD
Fei Wang, University of Maryland-College Park, College Park, MD
Ruth Oni, University of Maryland-College Park, College Park, MD
Meredith Melendez, Rutgers New Jersey Agricultural Experiment Station, Millville, NJ
Wesley Kline, Rutgers New Jersey Agricultural Experiment Station, Millville, NJ
Donna Pahl, University of Maryland-College Park, College Park, MD
Christopher Walsh, University of Maryland-College Park, College Park, MD
Kathryne Everts, University of Maryland, Salisbury, MD
Robert Buchanan, University of Maryland-College Park, College Park, MD
Introduction: Small- and medium-sized farms adopt a variety of cropping methods and irrigation water sources to cultivate tomatoes in the Mid-Atlantic region.  It is unclear how these practices affect the food safety risk for tomatoes. 

Purpose: The purpose of this study was to survey small- and medium-sized farms during pre-harvest tomato production in Maryland (MD), Delaware (DE) and New Jersey (NJ), to assess pathogen prevalence for Salmonella and Shiga toxin-producing Escherichia coli (STEC), and bacterial indicators.  Farms adopting both conventional and organic practices, and using surface or groundwater for irrigation, were included in the study.

Methods: Twenty-four organic and conventional farms were sampled for six weeks in MD, DE and NJ between July and September 2012. Tomato fruit, irrigation water, compost, field soil and pond sediment samples were collected. For tomato and soil samples, aerobic bacteria, E. coli and coliforms were enumerated using 3M petrifilms. Water samples were analyzed using standard membrane filtration.  The pathogens Salmonella and STEC were detected by enrichment in buffered peptone water followed by PCR amplification of sets of species-specific genes. 

Results: A total of 424 samples were collected in all, 259 of which were tomato samples. No Salmonella was detected.  One tomato (0.4%; n = 259) and 2 water samples (1.9%; n =  104) were positive for Shiga toxin genes (stx1 and stx2).  Generic E. coli was found in 5.4% (n = 259) of tomatoes, 28.8% (n = 104) of water and 11.5% (n = 61) of soil samples. E. coli levels varied by region, with higher counts detected in Western MD compared to other regions (P < 0.001). Total coliforms were present on 90% of tomatoes tested (n = 259), with an average of 4.1 log CFU/g. Aerobic bacteria on tomatoes varied by sampling time (P < 0.0001).   

Significance: These data provide crucial information about the microbial status of tomatoes grown in the Mid-Atlantic region in small- and medium-sized farms.

Back to: Poster Session 3 - Applied Laboratory Methods, Novel Laboratory Methods, Produce, Risk Assessment
<< Previous Abstract | Next Abstract >>