Serogroup variation with use of immunomagnetic separation to detect and isolate shiga toxin-producing escherichia coli o157 and the big six non-o157

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Abstract

Immunomagnetic separation (IMS) is a technique used for detection and isolation of Shiga toxin-producing E. coli (STEC) O157 and the six major non-O157 serogroups. Official testing protocols for STEC used by the U.S. Department of Agriculture (USDA) include IMS to aid with the recovery of presumptive positive cells. This study assessed the magnetic beads capture efficiency for the detection of STEC O157 and non-O157. IMS was performed to separate cell cultures in enrichment broth and in inoculated ground beef, using different bacterial concentrations. For E. coli O111, IMS required at least 5.0 log CFU/ml of the microorganism to be present in the sample, which suggests that improvement of the anti-O111 magnetic beads is needed. Other serogroups required 3.0 log CFU/ml for accurate detection. After reducing the bead solution volume to 50%, IMS effectively (P < 0.05) recovered the target cells when the minimum detection limit of the microorganism was present in the sample. Cell recovery using IMS may be affected by the target STEC serogroup and not by the bead volume used, which could be reduced to half. Therefore, it is important to acknowledge that IMS should be used for cell isolation rather than microbial detection.

Original languageEnglish
Pages (from-to)178-185
Number of pages8
JournalFood Protection Trends
Volume38
Issue number3
StatePublished - May 1 2018

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