Purpose: This study was undertaken to determine if Salmonella, artificially internalized into vegetable seeds, could migrate to different sections of sprouts/seedlings during germination process.
Methods: Alfalfa, fenugreek, lettuce and tomato seeds were artificially infiltrated with nalidixic acid-resistant Salmonella Montevideo, Salmonella Stanley, Salmonella Baildon or Salmonella Cubana. Contaminated seeds were germinated on 1% water agar in germination boxes at 25°C. Different sections of germinating seeds (whole seed, seed coat, cotyledon, stem, and root) were collected twice daily for 9 days for Salmonella enumeration. Each sample had ten replicates per trial, and two independent trials were conducted. Collected samples (n=512) were homogenized and aliquots of homogenates were spread-plated in duplicate on bismuth sulfite agar and tryptic soy agar supplemented with nalidixic acid. Obtained data were analyzed by Fisher’s LSD test using the R software.
Results: Cells of all four Salmonella strains migrated from contaminated vegetable seeds to different sections of the seedlings. Approximately 62% of the 512 samples tested positive for Salmonella. The average Salmonella population increased from 0.85 to 1.76 log CFU/seed section during seed germination. The highest Salmonella count was observed on cotyledons and seed coats (1.97 and 1.89 log CFU/seed section). Salmonella Montevideo had the lowest recovery rate of 0.72 log CFU/seed section, in comparison to 1.86, 1.85 and 1.75 log CFU/seed section for Salmonella Stanley, Salmonella Baildon and Salmonella Cubana. Salmonella populations recovered from fenugreek and alfalfa sprouts (2.76 and 2.35 log CFU/seed section) were significantly higher (P < 0.05) than those from tomato and lettuce seedlings (0.57 and 0.50 log CFU/seed section).
Significance: The study revealed the ability of Salmonella internalized in vegetable seeds to migrate to different sections of sprouts/seedlings during seed germination, emphasizing the importance of pathogen-free seeds for vegetable sprout production.