METHOD FOR DETERMINING THE PRESENCE OR ABSENCE OF SHIGA TOXIN-PRODUCING ESCHERICHIA COLI (STEC) IN A FOOD SAMPLE

摘要

A method for detecting the presence or absence of pathogenic STEC in food samples includes
incubating the food sample in a culture medium to obtain an E. coli stock medium;lysing the E. coli to obtain a E. coli DNA; andsubjecting the DNA to PCR, and amplifying the following genes or fragments thereof:
stx1 and/or stx2 encoding Shiga toxin 1 and Shiga toxin 2,for each STEC serogroup to be determined, the subtype of the eae gene of that serogroup encoding an intimin, andfor each STEC serogroup to be determined, a biomarker gene specific for that serogroup;

and, if stx1 and/or stx2 and the eae gene and the specific biomarker gene for at least one serogroup are amplified in the PCRs:
verifying the presence of the one or more specific serogroups of STEC by PCRs on concentrates of the E. coli stock medium.

主权项

1. A method for determining the presence or absence of one or more specific serogroups of pathogenic Shiga toxin-producing E. coli (STEC) in a food sample, comprising
incubating the food sample in a culture medium enabling growth of E. coli to obtain an E. coli stock medium; performing a lysis of the E. coli in the stock medium to obtain a sample solution comprising E. coli DNA; and subjecting the sample solution to a first series of polymerase chain reactions (PCR), using primers to amplify the following E. coli genes or fragments thereof:
stx1 and/or stx2 encoding Shiga toxin 1 and Shiga toxin 2, respectively,for each STEC serogroup to be determined, the subtype of the eae gene of that serogroup encoding an intimin, andfor each STEC serogroup to be determined, a biomarker gene specific for that serogroup; and, in case that stx1 and/or stx2 as well as the eae gene and the specific biomarker gene for at least one serogroup are amplified in the first series of PCRs: verifying the presence of the one or more specific serogroups of STEC by performing a second series of PCRs on concentrates of the E. coli stock medium and, optionally, a third series of PCRs on single E. coli colonies derived from the concentrates.