Monte Carlo Simulation of Pathogen Behavior during the Sprout Production Process

Abstract

Food-borne disease outbreaks linked to the consumption of raw sprouts have become a concern over the past decade. A Monte Carlo simulation model of the sprout production process was created to determine the most-effective points for pathogen control. Published literature was reviewed, and relevant data were compiled. Appropriate statistical distributions were determined and used to create the Monte Carlo model with Analytica software. Factors modeled included initial pathogen concentration and prevalence, seed disinfection effectiveness, and sampling of seeds prior to sprouting, sampling of irrigation water, or sampling of the finished product. Pathogen concentration and uniformity of seed contamination had a large effect on the fraction of contaminated batches predicted by the simulation. The model predicted that sprout sampling and irrigation water sampling at the end of the sprouting process would be more effective in pathogen detection than seed sampling prior to production. Day of sampling and type of sample (sprout or water) taken had a minimal effect on rate of detection. Seed disinfection reduced the proportion of contaminated batches, but in some cases it also reduced the ability to detect the pathogen when it was present, because cell numbers were reduced below the detection limit. Both the amount sampled and the pathogen detection limit were shown to be important variables in determining sampling effectiveness. This simulation can also be used to guide further research and compare the levels of effectiveness of different risk reduction strategies.Seeds and bean sprouts have become a serious food safety concern during the past decade. Outbreaks of salmonellosis and food-borne illness from pathogenic Escherichia coli have been linked with contaminated sprouts. These outbreaks have been most commonly associated with alfalfa sprouts but have also been linked to clover, radish, and mung bean sprouts.

Risk Assessment of Salmonellosis from Consumption of Alfalfa Sprouts and Evaluation of the Public Health Impact of Sprout Seed Treatment and Spent Irrigation Water Testing

“…A review of studies in the scientific literature shows that when seed samples are positive, the pathogen contamination levels in seeds are low, as is typical for Salmonella in low water activity foods . Montville and Schaffner used a “low” contamination level of 1–5 cells per 25 g units, and a “high” contamination level of 100 – 5,000 CFU/25 g as assumptions, but they did not cite any studies for their choice of the “high” contamination level (i.e., the high levels were hypothetical). Reported Salmonella levels for seeds in two different seed lots associated with outbreaks were 1.3 ± 0.4–1.6 ± 0.2 cells per 100 g .…”

“…Two microbial risk assessments have been published to evaluate contamination and risk associated with sprouts . The model reported by Montville and Schaffner predicts the behavior of bacterial pathogens (including Salmonella and E. coli O157:H7) during sprouting to determine the likelihood of sprout production batch contamination and the relative effect of preproduction sampling and postproduction sampling on the likelihood of detecting batch contamination. This model used hypothetical prevalence and levels for pathogens in seeds.…”

Flow cytometry for rapid detection of Salmonella spp. in seed sprouts

“…The high discriminatory power of FCM, coupled with our DNA-FISH method enabled us to detect relatively low levels of S. Typhimurium (10 4 CFU g 1 sprouts/10 3 CFU ml 1 sprout wash) against very high levels (10 8 CFU g 1 ) of physiologically similar or closely-related bacteria and additional particulate matter. Monte Carlo simulations of pathogen behavior during sprouting suggest that probabilities of detecting pathogens in sprout samples are high when methods able to detect 10 4 or fewer cells per gram are used [51].…”

Development of Effective Seed Decontamination Technology to Inactivate Pathogens on Mung Bean Seeds and Its Practical Application in Japan

“…The assurance of the absence of pathogens on seeds 42,51 . Many other chemical agents were studied to decontaminate the sprout seeds.…”