11th October 2016 Content supplied by: Health Protection Scotland
E.coli O157 in Raw Milk Cheese - Company Disputes Ban
A child’s death from E. coli O157 infection has lead to a dispute over the recall of the implicated cheese products. The affected child was just one of 20 confirmed infection cases detected between the 2nd to 15th of July 2016, 11 of whom were treated in hospital.
Health Protection Scotland (HSP) investigations identified the Dunsyre blue cheese (made from unpasteurised milk) as the most likely cause of the outbreak however the company firmly disputed the evidence insisting that their cheeses are safe to eat based on their independent and external testing. HSP however found that of those affected, the majority had consumed the cheese product before falling unwell adding that despite their widespread investigation efforts, no other link could be established to the majority of cases of this incident.
As a result, Food Standards Scotland (FSS) have administered a ban on all cheese products made by the producer, Errington Cheese who are based in South-Lanarkshire.
Hugh Pennington, Emeritus Professor of bacteriology at the University of Aberdeen disagreed stating “the FSS are behaving in a very precautionary manner” and that it raises an issue of proportionality because whilst some people who ate the cheese were sickened with E. coli O157 a significant number who didn’t eat the cheese also fell ill.
The alert was initially issued in July with sales being withdrawn shortly after, however the Errington Cheese company has remained firm on its position that its repeated testing methods found no traces of E. coli in any of the cheese products involved. On the other hand, the FSS has stated that two batches of Dunsyre cheese “were implicated based on epidemiological evidence”, testing positive for E. coli O157 and that the recall, in light of evidence is in the best interests of consumer public health.
Microbiologically speaking, discrepancies were found between FSS testing and the independent testing results. Discrepancies in testing results can occur and require an understanding of how the microorganisms might be distributed within a food product and of the difference between prevalence and concentration of contamination. Although laboratory or sampling errors are easy explanations, others should also be considered such as a non-random or heterogeneous distribution; low prevalence of contamination as well as pathogen die off between original and repeat tests. If distribution is homogenous, there is an equal opportunity for contamination to occur at any stage and time of operation whilst if heterogeneous, random sampling may not be sufficient to detect the organism.
The latest statement issued by the traditional cheese company on 15th September 2016 reaffirms their positions that all the testing they carried out on their cheese found no trace of the pathogenic E. coli O157 which included micro testing laboratories in the UK and Europe.
This case highlights the difficulty in linking a suspect batch of food product to an outbreak as distribution of the pathogen may have occurred in such a way that consumers have eaten the evidence. Detailed analysis by DNA testing of each organism detected in all affected patients would help to prove a direct link and that there could be more than one source of the outbreak.
Date Published: 11th October 2016
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