Survival of Contaminated Water Spray on the Survival of Escherichia coli on Field-grown Tomatoes

According to the Centers for Disease Control and Prevention, between 1998 and 2008 fresh produce was responsible for 46 percent of foodborne illnesses and 23 percent of food-related deaths in the United States. Among the possible sources of produce contamination, water used for irrigation and agricultural sprays is a prime concern. In this study, the persistence and survival of total coliforms and generic E. coli, on field-grown tomatoes irrigated with contaminated water was evaluated in a randomized complete block experiment (reps=4, plants/rep=15). Tomato plants (variety: BHN 602 VFFF Hybrid) at breaker, pink or red-ripe stage were spray-inoculated 10-days before final harvest with non-chlorinated water containing fresh bovine manure to achieve target cell populations of 0, 100, 1000, and 10000 generic E. coli/100mL. On days 0 (pre- and post-inoculation), 1, 3, 5, 7, and 9, tomatoes (n=15, plot) were analyzed for total coliforms and generic E. coli. Populations of total coliforms and generic E. coli ranged from 2.58 to 4.95 and 0 to 3.14 cfu/g, respectively, during the 9-day study. These results show that under the field conditions of this study generic E. coli present in initially detectable and high concentrations in sprays do not survive on tomato fruits exposed for 9 days. Further research is needed to determine the influence of specific environmental factors on E. coli survival on tomato fruits prior to harvest.