Comparison of IMS Platforms for Detecting and Recovering Escherichia coli O157 and Shigella flexneri in Foods

Abstract

Two automated platforms using immunomagnetic separation technology were compared for detecting and recovering Escherichia coli O157 in ground beef and sprouts and Shigella flexneri in green onions. The foods were inoculated with <20 CFU/25 g and tested at 5 and 24 h postincubation. Immunomagnetic beads were mixed with food enrichments, processed through the Pathatrix Auto or KingFisher Flex, and tested by real-time PCR (qPCR) and recovery on selective agars. At 5 h, the Pathatrix Auto detected E. coli O157 in 90% and 60% of the ground beef and sprouts samples and S. flexneri in all of the green onion samples. It also recovered E. coli O157 in all the samples but could not recover S. flexneri in any of the green onion samples. In comparison, the KingFisher Flex detected E. coli O157 in 80% and 30% of the ground beef and sprouts samples and S. flexneri in all of the green onion samples. It also recovered E. coli O157 in 90% of the ground beef samples but none of the sprouts samples and S. flexneri in 20% of the green onion samples. At 24 h, both platforms detected and recovered the target bacteria in all of the samples.