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Diagnosis is usually made from a stool sample.
Culture confirmation of E. coli O157 at the diagnostic laboratory will take 24-48 hours from receipt of the sample (local confirmation). In general, this is obtained by the following steps:
1. Examination of colonial morphology on selective media (day 1);
2. Performing a slide agglutination test on single colonies (this is usually an E. coli O157 kit- based test) (day 1);
3. Confirmation of the identity of slide agglutination positive colonies as E. coli (usually day 2).
When all 3 steps have been carried out, the isolation of E. coli O157 from the sample is `locally confirmed`.
Confirmed case: positive STEC culture or PCR shiga toxin positive result from PHE gastrointestinal bacteria reference unit (GBRU) (with or without clinical features, with or without epidemiological link to a confirmed case)
Confirmed STEC-related HUS:
Probable STEC-related HUS
Epidemiological link – epidemiological link to a confirmed case, awaiting results of microbiological testing OR diagnostic/local laboratory PCR shiga toxin positive, with or without clinical features of STEC
PCR probable - diagnostic/local laboratory PCR shiga toxin positive BUT negative culture for STEC O157, bloody diarrhoea/hospitalisation for acute diarrhoea, without epidemiological link to a confirmed case