Efficacy of Ascaroside #18 Treatments in Control of Salmonella enterica on Alfalfa and Fenugreek Seeds and Sprouts

Abstract

A novel, natural, and effective antimicrobial intervention is in demand for improving the microbial safety of vegetable seeds/sprouts. This study assessed the efficacy of ascaroside treatment in the control of Salmonella enterica on alfalfa and fenugreek sprouts. Sanitized commercial seeds were treated with 1 mM or 1 µM ascaroside (ascr)#18, a plant immunity modulator (PIM) and dried for an hour before being inoculated with lyophilized S. Cubana or S. Stanley cells in sandy soil (10⁴ CFU/g). Treated and untreated seeds were spouted on 1% water agar at 25°C in the dark. Seed or sprout samples were collected on days 0, 1, 3, 5, and 7, and the population of Salmonella was determined. Data were fit into the general linear arrangement, and means were separated using Fisher's least significant difference test. Seed type, strain type, treatment type, and sprouting time were significant factors (P ≤ 0.05) influencing Salmonella growth on sprouts. The populations of Salmonella were significantly higher on fenugreek than on alfalfa sprouts. S. Stanley had a significantly higher population than S. Cubana. The population of Salmonella increased from day 0 to day 3 and reached the peak population on Day 5. Treatments with both concentrations of ascaroside significantly decreased the populations of Salmonella compared to the controls. The mean Salmonella population reduction was ca. 4 or 1 log CFU/g by treatment with 1 mM and 1 µM of the PIM, respectively. Treatment with the PIM could be potentially used to improve the microbial safety of vegetable seeds and sprouts.

Keywords: Ascr#18; Plant immunity modulator; Salmonella enterica; Sprout seeds; Vegetable sprouts.