Evaluation of Risk Factors Affecting Transmission and Persistence of <i>Salmonella </i>spp. in Hydroponically Grown Tomatoes

Coleman, Shannon

Monday, August 4, 2014

Exhibit Hall D (Indiana Convention Center)

Shannon Coleman, Colorado State University, Fort Collins, CO

Bledar Bisha, University of Wyoming, Laramie, WY

Kelly Blume, Colorado State University, Fort Collins, CO

Vanessa Sandoval, Colorado State University, Fort Collins, CO

Nicholas Drury, Colorado State University, Fort Collins, CO

Holly Kesseler, Colorado State University, Fort Collins, CO

Alma Perez-Mendez, Colorado State University, Fort Collins, CO

Jeffrey Chandler, University of Wyoming, Laramie, WY

Ben Franz, Colorado State University, Fort Collins, CO

Ryan Jaebker, Colorado State University, Fort Collins, CO

Donald Schaffner, Rutgers, The State University of New Jersey, New Brunswick, NJ

Jeffrey LeJeune, The Ohio State University, Wooster, OH

Marisa Bunning, Colorado State University, Fort Collins, CO

Steven Newman, Colorado State University, Fort Collins, CO

Lawrence Goodridge, Colorado State University, Fort Collins

Introduction: Over one million foodborne illnesses cases are attributed to Salmonella annually in the U.S. Greenhouse/hydroponic production of tomatoes has made a significant impact on the U.S. fresh-tomato market. There is little known about the possibility of contamination and internalization via greenhouse/hydroponic commercial production since these operations are usually considered relatively sanitary due to the closed environment.

Purpose: The objective of this study was to investigate the survival of Salmonella spp. in nutrient solutions used for commercial hydroponic tomato systems, as well as to determine if continuous inoculation of nutrient solution with Salmonella through a contaminated water source would lead to contamination in tomato fruits, leaves, roots and the formation of biofilms.

Methods: An avirulent strain of Salmonella Typhimurium was inoculated at 10⁵ CFU/ml in nutrient solution tanks of hydroponic tomato systems. Inoculation occurred on day zero and every two weeks for twelve weeks. Non-inoculated tanks served as controls. On day zero and every other day post inoculation, the nutrient solution was analyzed by plating. Leaves and biofilm samples were collected on day zero and every two-weeks post inoculation. Fruit samples were collected six-weeks post inoculation. Leaf, fruit and root samples were analyzed using enrichment and plating methods. Biofilm coupons were analyzed using a tape FISH method. Typical Salmonella colonies observed from leaf, fruit, and root samples were confirmed by riboprinting.

Results: There was a two-log reduction of the cells two days post-initial inoculation. Reduction of cells continued over the two-week inoculation period with few cells surviving until the next inoculation period. Contamination occurred significantly in the root systems. In contrast, no contamination occurred in the leaf, fruit, and biofilm samples.

Significance: The results of the study show that while contaminated hydroponic nutrient solution or water leads to Salmonella contamination of tomato plant root, such an event may not pose a risk of Salmonella contamination of hydroponically grown tomatoes.

P1-118 Evaluation of Risk Factors Affecting Transmission and Persistence of Salmonella spp. in Hydroponically Grown Tomatoes