Effects of Disinfectants on Decontamination of Salmonella Newport in Irrigation Well and Pond Water

Introduction: More than 20% of outbreaks of foodborne diseases have been traced back to contaminated fresh produce. Pre-harvest has been proposed to be one of the most likely points of original contamination, and irrigation water has been reported as one of the main contamination sources. However, little is known about the efficient methods for the decontamination of Salmonella enterica in irrigation water.

Purpose: To evaluate the efficacy of disinfectants, Clorox Regular-Bleach (sodium hypochlorite), Oxidate Broad Spectrum Bactericide Fungicide (hydrogen peroxide) and Sanidate 12.0 (hydrogen peroxide and peroxyacetic acid), on the reduction of S. enterica serovar Newport in irrigation water.

Methods: In this study, well and pond irrigation water were collected from different vegetable farms on Eastern Shore of Virginia. Three initial levels of Salmonella Newport (10⁸, 10⁶ and 10⁴ CFU/ml) and two application levels of disinfectants (1:1,000 or 1:50,000 dilution) were tested in this study. Bacterial concentration was measured 30 min after treatment.

Results: Salmonella Newport in irrigation well and pond water was not detectable after application of the three disinfectants tested in this study at the initial bacterial level of 10⁴ CFU/ml. Sanidate 12.0 is the most efficient disinfectant for water treatment with high Salmonella concentration. The efficacy of the disinfectants was lower for pond water treatment than that for well water treatment. Water pH was changed after the disinfectant treatments especially applied with higher concentration of sanitizers.

Significance: These results would bring clues to manage Salmonella contamination in irrigation water for vegetable and fruit production.