Only two of more than 300 samples of beef and minced meat were positive for Shiga toxin-producing E. coli in Norway, according to a survey.

The analysis of Shiga toxin-producing E. coli (STEC) in 308 ground meat products was done by the Veterinary Institute on behalf of the Norwegian Food Safety Authority (Mattilsynet). The former analyzed the samples in 2018 which were collected by the latter in stores across the country in 2017.

Results indicate a good situation in Norway with low occurrence of STEC that may cause serious illness.

In recent years there has been an increase in the number of people infected by STEC in Norway. In 2018, 494 cases were reported, but many were infected abroad and by foods other than beef. Ruminants such as cattle and sheep are considered the main source of STEC, according to the report. Past surveys in Norwegian meat products were carried out years ago and mainly focused on E. coli O157:H7.

Results from a survey of E. coli in cattle from 2014 to 2017 indicated a low occurrence of STEC serogroups O26, O91, O103, O111, O121, O145 and O157 in Norwegian dairy herds. The Norwegian Food Safety Authority commissioned a survey of STEC in meat products.

Sample analysis and findings
Enriched samples were screened for presence of the genetic markers stx1, stx2 and eae. Samples positive for stx and eae were then screened for the genetic markers for serogroups O26, O91, O103, O121, O145 and O157. After screening, isolation was done from samples positive for virulence markers and one or more of the serogroups. Isolates identified as STEC were further characterized by whole genome sequencing.

Results indicate the occurrence of STEC serogroups O91, O103, O111, O121, O145 and O157 is low. Atypical enteropathogenic E. coli (aEPEC) and E. coli without virulence factors belonging to these serogroups were isolated.

A total of 70 samples were positive for stx2 in the initial work and they were included in further studies for stx2a. Using real-time PCR, the stx2a gene was detected in nine of the 70 samples. From two of these samples E. coli was isolated with stx2a. The analysis found 27 samples positive for stx1 and 64 with the eae gene.

The two positive samples contained STEC O26:H11 (stx1a and eae positive) and STEC O91:H21 (stx2b positive).

Both agencies said the survey provides important and updated knowledge for industry, authorities and educational institutions. They added such work should be done at regular intervals to generate updated Norwegian data.

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