[Detection methods of enterohemorrhagic Escherichia coli O111 in beef: a collaborative study].

Abstract

To establish a detection method for enterohemorrhagic Escherichia coli (EHEC) O111 in meat, a single-laboratory evaluation and a collaborative study were conducted focusing on comparisons of the efficiencies in combination with enrichment, a direct plating method and a plating method with immunomagnetic separation (IMS-plating method) using various agar media for EHEC O111, loop-mediated isothermal amplification (LAMP) assay targeting the Verocytotoxin (VT) gene as a molecular detection method. On a single-laboratory evaluation, enrichment in modified EC at 36 degrees C was inferior to that in modified EC supplemented with novobiocin (NmEC) and mEC at 42 degrees C to isolate EHEC O111 by plating methods. On a collaborative study, there were no significant differences between combinations of enrichment in NmEC at 42 degrees C-LAMP assay and enrichment in mEC at 42 degrees C-LAMP assay. The combinations of enrichment in NmEC at 42 degrees C-direct plating and enrichment in NmEC at 42 degrees C-IMS-plating were superior to combinations of enrichment in mEC at 42 degrees C-direct plating and enrichment in mEC at 42 degrees C-IMS-plating (p<0.05). There were no significant differences among the six different agar media by the direct plating and IMS-plating methods. As a result, it was suggested that the following methods are adequate for detection of EHEC O111 in beef: combinations of enrichment in NmEC at 42 degrees C, and direct plating and IMS-plating methods, or LAMP assay as a screening assay to detect VT gene followed by direct plating and IMS-plating methods.