P1-38 The Impact of Heavy Rainfall on Salmonella Survival and Transport

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Debbie Lee , Emory University , Atlanta , GA
Timothy Coolong , University of Georgia , Tifton , GA
George Vellidis , University of Georgia , Tifton , GA
Karen Levy , Emory University , Atlanta , GA
Introduction: Salmonella has been regularly detected in surface water in southern Georgia but many farms in the region use surface water ponds adjacent to produce fields for irrigation. We recently detected Salmonella in irrigation ponds, irrigation systems, and produce on a commercial farm in southern Georgia; however, the sources of contamination were unclear.

Purpose: This study investigated the impact of irrigation on Salmonella survival in soil and on crops and the ways in which antecedent soil moisture conditions may modify the effect of an extreme rainfall event on Salmonella transport through splash and runoff.

Methods: Eight plots (2’ by 10’) of cabbage were inoculated with avirulent, ampicillin-resistant gfp-marked Salmonella. Half of the plots were subject to routine overhead irrigation while the other half of the plots were kept dry for eight days. Plots were reinoculated and then subjected to a heavy rainfall event (four inches/hour) with a rainfall simulator to determine the difference in Salmonellaconcentrations in soil and on cabbage leaves before and after the extreme rainfall event.

Results:  Salmonella concentrations in soil and crops decreased over eight days with no significant differences between the wet and dry plots. Salmonella concentrations in soil and cabbage in both plot types decreased following the heavy rainfall event but were still detectable in samples from both plot types in low concentrations. Salmonella concentrations in soil and splash water were higher in the plots receiving routine overhead irrigation plots, although this difference was not statistically significant.

Significance:  Study results indicate a potential concern for produce safety because Salmonella can persist on crops and in soil and that Salmonella can be transported through rainfall splash. Produce contamination risk may be greater when high levels of soil moisture are maintained. This research will help growers mitigate crop contamination risk by elucidating the timing of highest concern for contamination via splash.