Levels and Distribution of Salmonella in Naturally Contaminated Cashews
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EmailNaturally contaminated raw materials associated with foodborne illness outbreaks are rarely available for evaluation of concentration and distribution of the outbreak pathogen.
Introduction: Naturally contaminated raw materials associated with foodborne illness outbreaks are rarely available for evaluation of concentration and distribution of the outbreak pathogen.
Purpose: To evaluate the levels and distribution of Salmonella present in naturally contaminated raw cashews linked to a salmonellosis outbreak associated with a fermented cashew “cheese.”
Methods: Two unopened 22.7-kg boxes from a single lot of the cashew kernel pieces were each divided into seven approximately equal units. Three 10-g subsamples per unit were evaluated for aerobic plate count (APC), coliform counts, and Escherichia coli counts, and 10 50-g subsamples per unit were enriched for the presence of Salmonella using modified FDA BAM methods. Presumptive Salmonella-positive colonies were confirmed using CHROMagar Salmonella and real-time PCR (InvA) and then serotyped using standard methods and genome sequencing prediction tools. Most-probable-number (MPN) values were determined.
Results: APC and coliform counts ranged from 1.81 to 5.47 (mean 2.44 ± 0.63 log CFU/g) and 0.60 to 5.20 (mean 1.74 ± 0.80 log CFU/g), respectively. Salmonella was recovered from four (Box 1) or seven (Box 2) units. One of 10 subsamples was positive in all but four units; one (Box 1) and three (Box 2) units had two positive subsamples. The MPN value for the two boxes was 0.0023 MPN/g (95% CI: 0.0014 to 0.0038). Salmonella Urbana was isolated from three subsamples in Box 1 and eight in Box 2. Salmonella Fresno and Vinohrady were unique to single subsamples from Box 1, and Salmonella Nima was unique to two subsamples from Box 2. Of the four serovars recovered, Salmonella Urbana is the only one in common with four reported outbreak-associated serovars.
Significance: Understanding the distribution and concentration of Salmonella in naturally contaminated cashews provides important information for hazard analysis and risk assessments for soaked and fermented cashew-based products.
