P1-156 Impact of Exceptional Situations Occurring Prior to Microbial Reduction Treatment on the Risk of Human Salmonellosis Arising from the Consumption of Pistachios in the United States: A Quantitative Assessment

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Gordon Davidson , U.S. Food and Drug Administration , College Park , MD
Sofia Santillana Farakos , U.S. Food and Drug Administration , College Park , MD
Regis Pouillot , U.S. Food and Drug Administration, CFSAN , College Park , MD
Rhoma Johnson , U.S. Food and Drug Administration , College Park , MD
Judith Spungen , U.S. Food and Drug Administration , College Park , MD
Insook Son , U.S. Food and Drug Administration , College Park , MD
Nathan Anderson , U.S. Food and Drug Administration , Bedford Park , IL
Jane Van Doren , U.S. Food and Drug Administration , College Park , MD
Introduction: Detection of Salmonella on pistachios demonstrates the need to quantify how various events impact the risk from consumption of this tree nut. 

Purpose: To conduct a quantitative risk assessment of human salmonellosis arising from the consumption of pistachios in the U.S. and to evaluate the impact of exceptional situations occurring prior to microbial reduction treatment.

Methods: A baseline exposure assessment model was developed that includes Salmonella prevalence and levels on floater and sinker pistachios in silo storage, microbial reduction treatment (0-5 log CFU), Salmonella persistence during post-processing and retail storage, and consumption levels. Exceptional situations occurring prior to microbial reduction treatment, including increasing the prevalence and levels of Salmonella cross-contamination in a float tank, Salmonella growth due to a delay in drying hulled pistachios, and Salmonella recontamination by pests in the storage silos, were each modeled with a subsequent microbial reduction treatment (0-5 log CFU). A homogeneous distribution of the Salmonella cells was assumed. Risks per serving and per exceptional situation were calculated using Monte Carlo simulations developed in R using the mc2d package. Variability was set to 10,001 replicates and uncertainty dimension to 501 replicates; these were modeled independently. 

Results: The baseline model predicted a 90% reduction in risk of salmonellosis for each log of microbial reduction treatment level applied. The predicted relative risk of illness per pistachio serving was higher in the modeled exceptional situations – Salmonella cross-contamination in a float tank (6.8 to 7.5-fold higher), Salmonella recontamination by pests in the silos (1.0 to 1.2-fold higher), and Salmonella growth due to a delay in drying (1.1 x 102 to 4.3 x 108-fold higher) – when compared to the baseline model. 

Significance: While process control through microbial reduction treatment is predicted to significantly reduce the risk from pistachio consumption, certain pre-processing exceptional situations may contribute to increased risk.