P2-12 Intercellular Production of H2O2 in Tomatoes as a Prevention to Salmonella Proliferation

Thursday, May 12, 2016
Megaron Athens International Conference Center
Gabriel Sutton, Middlesex University, London, United Kingdom of Great Britain and Northern Ireland
Massimiliano Marvasi, Middlesex University, London, United Kingdom
Max Teplitski, University of Florida, Gainesville, FL
Introduction: Due to increases in produce associated gastroenteritis, it is becoming clearer that we know little about the ecology of human pathogens in vegetables. Previous research has shown that Salmonella (14028) can grow in numbers up to 105 compared against the initial inoculum. It was also found that Piccolo (cherry) tomatoes were generally less conductive to Salmonella than any of the larger cultivars (up to 2 logs less). 

Purpose: We hypothesise that cherry tomatoes naturally produce higher levels of H2Oin their intercellular fluid than larger tomatoes.

Methods: Around 100 cells of Salmonella were inoculated in wounds under the pericarp in both the cherry and Alicante (larger) tomatoes. Salmonella proliferation was measured after a week of incubation by plating on Xylose lysine deoxycholate agar (XLD agar). To test H2O2 levels a novel method was used. Small pieces of the pericarp (from both cultivars) totalling 2g were subjected to a pressured vacuum to infiltrate distilled water into the intercellular space. The pieces were then spun in a centrifuge to extract all fluid from the intercellular space. Samples were de-proteinised using 10kD spin columns. A fluorometric assay was then used to test the concentration of H2O2. Four biological and two technical replicas were carried out. 

Results: The increase of Salmonella from one week of initial incubation was up to 104 CFU/tomato in Alicante cultivar, and 102 CFU/tomato in the cherry cultivar. The difference in Salmonella proliferation was significant (α=0.05). The cherry tomatoes showed an average of 0.76nmol/ml of H2O2 whereas the Alicante cultivar showed an average of 0.46nmol/ml. The difference in H2Oconcentration between the tomato cultivars was significant. 

Significance: These findings open opportunities into genetic research of the tomato. The oOxyR gene in Salmonella activates the regulon of H2O2 inducible genes. Such pathways can be involved in Salmonella proliferation in tomatoes.