P1-50 Recovery of Salmonella Agona and Typhimurium on Sprouting Alfalfa after Seed Sanitation

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Yue Dai , University of British Columbia , Vancouver , Canada
Pascal Delaquis , Agriculture and Agri-Food Canada , Summerland , Canada
Carmen Wakeling , Eatmore Sprouts & Greens Ltd. , Courtenay , Canada
Siyun Wang , Food, Nutrition and Health, University of British Columbia , Vancouver , Canada
Introduction: Alfalfa sprouts contaminated with Salmonella have been the source of many foodborne disease outbreaks in North America. Although treatments recommended by the Canadian Food Inspection Agency (CFIA) achieve a minimum three log reduction immediately after sanitation, previous research has shown that Salmonella can proliferate during germination. The recovery of Salmonella after sanitation is of great interest as it may explain the persistence on sprouted vegetables.

Purpose: The purpose of this study was to investigate the ability of Salmonella Agona and Typhimurium to grow on alfalfa sprouts after CFIA-recommended seed treatments and a treatment compliant with organic production principles.

Methods: Alfalfa seeds inoculated with Salmonella Agona PARC 5 isolated from alfalfa sprouts or Salmonella Typhimurium PARC 64 (4.67±0.26 log CFU/g) were subjected to three types of sanitizing treatments: 5,000 ppm chlorine, 8% hydrogen peroxide, and an organic treatment (50°C hot water, 2% hydrogen peroxide, and 0.1% acetic acid). The sanitized seeds were sprouted and Salmonella were recovered on xylose lysine deoxycholate agar during germination. Survival curves were plotted and compared using one-way ANOVA.

Results: The density of both Salmonella serovars increased from <10 CFU/g immediately after treatment to 5.5 to 7.5 log CFU/g after six days of germination. The lag phase of both serovars, after the chlorine treatment, were significantly shorter (P<0.05) compared to those after the other two treatments. The maximum growth rate of Salmonella Agona was greater (P<0.05) than Typhimurium. For instance, the cell density of Salmonella Agona reached 7.34±0.27 log CFU/g 24 hours after the chlorine treatment versus 5.77±0.51 and 6.87±0.14 log CFU/g after the hydrogen peroxide and the organic treatments, respectively.

Significance:   These data show that Salmonella cells were able to recover and grow on sprouting alfalfa seeds. More lethal treatments need to be devised for production of pathogen-free sprouted vegetables.