Purpose: The aim of this study was to evaluate the effect of pesticides on the growth and survival of the foodborne human pathogens E. coli O157:H7 and Salmonella Typhimurium.
Methods: Eight pesticides that are commonly used on leafy greens and/or tomatoes were tested at three concentrations, ranging from the lowest to highest as recommended in their applications. Each pesticide solution was prepared in sterile distilled water containing ca. 4 log CFU/ml of each pathogen individualy and incubated at 21 °C. The population of each human pathogen in pesticide solution was monitored up to 24 h.
Results: The fungicide/bactericide copper hydroxide (Kocide); and the insecticides Assail, Mustang and Ambush were significantly (P < 0.05) inhibitory to both pathogens in a concentration dependent manner. The fungicide chlorothalonil (Bravo), and the insecticides Beleaf and Intrepid did not show significant effect on both pathogens. However, the fungicide azoxystrobin (Quadris) showed a significant (P < 0.05) stimulatory growth effect only on E. coli O157:H7 after 6 h of incubation at 21 °C.
Significance: The findings of this study indicate that, depending on the specific pesticide, some may serve as a potential carrier of human pathogens to fresh produce if contaminated water is used in their preparation, whereas others could be an additional barrier to such a contamination event. This information is critical in risk assessment of food safety of fresh produce.