Two Processing Methods for the Isolation of Salmonella from Naturally Contaminated Alfalfa Seeds

Abstract

Two processing methods were examined for the recovery of Salmonella from naturally contaminated alfalfa seed. Seed samples, from each of three investigations, were processed by sprouting and shredding before preenrichment and culture. In lot A, Salmonella serotype Newport was isolated from 3 of 30 sample units with the sprouting method and 2 of 30 with the shredding method. In lot B, three serotypes in various combinations were isolated from 10 of 30 sample units with the sprouting method and 9 of 30 with the shredding method. In lot C, Salmonella group C₁ was isolated from 27 of 30 sample units with the sprouting method and 24 of 30 with the shredding method. Additionally, serotype Newport was found in one lot C sample unit. Using shredded seed data, a most probable number (MPN) for Salmonella contamination per lot was calculated. Serotype Newport was estimated at 0.07 MPN/100 g in lot A; the concentration for three serotypes was estimated to be 0.36 MPN/100 g in lot B; Salmonella group C₁ was estimated at 1.8 MPN/100 g in lot C. Our success in isolating Salmonella from alfalfa seeds was likely attributed to the volume of material tested and the quick acquisition of the seeds after the outbreak was identified. Shredding the seeds was easier and yielded definitive results more quickly than sprouting.