P3-130 Salmonella Survival in Florida Tomato Field Soil under Different Simulated Environmental Conditions

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Angela Valadez, University of Florida, Lake Alfred, FL
Michelle Danyluk, University of Florida, Lake Alfred, FL
Introduction: The time between tomato harvest and field preparation for the next crop of tomatoes in Florida can range from two to five months, depending on the production district. The risks associated with Salmonellasurvival during the off-season of tomato production have not been investigated.

Purpose: The aim of this study was to investigate the potential for Salmonella to persist in tomato field soil with and without the addition of tomato plant debris.

Methods: A cocktail of rifampicin-resistant Salmonella serotypes Montevideo, Javiana, Anatum, Braenderup, and Newport, were inoculated at high and low (7 and 4 log CFU/ml) concentrations into soils collected from four tomato-growing regions in Florida (Collier, Dade, Gadsden, and Manatee counties). The soils were further divided into four composites (soil (S), soil and plant (SP), soil and tomato (ST), and soil, tomato, and plant (STP)). Soils were stored at 15°C or 30°C for 3 months. Salmonella populations were enumerated on rifampicin supplemented selective and non-selective agars (n = 3).

Results: At 30°C, Salmonella populations declined between 0.72 (S, high) and 0.06 (SD, high), 0.66 (ST, high) and 0.27 (SD, low), 0.73 (S, high) and 0.05 (SD, low), and 0.92 (STP, low) and 0.06 (SD, high) log CFU/g/day, in tomato field soils from Collier, Dade, Gadsden and Manatee counties, respectively. 

At 15°C, the rates of Salmonella decline ranged between 0.62 (S, high) and 0.13 (STP, low), 0.9 (ST, high) and 0.08 (STP, low), 1.4 (ST, high) and 0.22 (STP, low), and 0.94 (ST, high) and 0.03 (STP, high) log CFU/g/day, in soil from tomato fields from Collier, Dade, Gadsden and Manatee counties, respectively.  After 90 days, populations were detectable in all conditions evaluated by enrichments of 10 g samples.

Significance: Salmonella can persist in Florida’s tomato field soils during the off-season of tomato production and may be a source for pathogen contamination in produce fields between tomato seasons.