A research note: the potential for transfer of Salmonella from irrigation water to tomatoes

The transmission of Salmonella Enteritidis from soil to fruit by contaminated irrigated water was studied using 20 patio tomato plants. In order to track the presence of Salmonella in the soil and plants a luminescent strain transformed with the full luxCDABE gene cassette from Photorhabdus luminescens was used. The tomato plants were irrigated every other day by direct application of water containing Salmonella Enteritidis (10^5 CFU ml^-1) to the soil. Samples of soil, stem, leaf and fruit were taken weekly and assayed for Salmonella by plating onto Luria Bertani agar containing 50 g ml^-1 ampicillin. There was a significant difference (P <(less than)0.05) in Salmonella counts from soils sampled during the course of the study. No Salmonella were recovered from the leaf, stem, and fruit samples taken from the tomato plants. This indicates that, under these test conditions, watering with contaminated water directly into the soil does not result in the transmission of Salmonella, and possibly other pathogens, to tomatoes.