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E. coli O55 outbreak in Dorset

Posted by: , Posted on: - Categories: Bacterial diseases

As Senior Molecular Biologist at APHA, my team and I play a key role in detecting the emergence and minimising the spread of zoonotic bacterial pathogens in order to reduce the risk to human health.

E. coli

E. coli is a type of bacteria which normally inhabits the intestines of animals and humans, but also occurs in the environment, for example in soil and water.

Although most strains are harmless, VTEC (Verotoxigenic Escherichia coli which produces the verocytotoxin) strains can cause severe illness in humans.

Many animals can carry VTEC, usually without any clinical symptoms or disease.

Outbreak in Dorset

For the past 18 months, my team have been working closely with vets in APHA and experts in Public Health England (PHE) who are interested in uncovering the source of a serious outbreak of human illness in Dorset caused by Escherichia coli (E. coli) O55, a type of E. coli which had never previously been found in an outbreak in the UK.

The BBC were interested in showing the work going on behind the scenes, such as the tests my team is developing for detection of O55, to help uncover the source of the outbreak. This was part of a documentary for BBC Inside Out South which showed how E. coli O55 infection had affected the people involved.

APHA's role

APHA will carry out tests for detection of E. coli pathogens present in animals when there is a suspected link between human cases and certain animal species. Our scientists had previously used a test for VTEC O157 in animal faeces as this strain is the most common cause of VTEC outbreaks among people in the UK.

When the Dorset outbreak occurred development of a test for VTEC O55 in animals became a priority for my team of scientists.

The procedure

The test is based on the use of specially coated tiny metal beads which attach to the strain of bacteria that is to be measured. The first step is to prepare the beads so that they will be able to attach to E. coli O55. Then they are tested to ensure that they will detect E. coli O55 in samples with the required specificity and sensitivity.

Once the team is satisfied that the new test is detecting E. coli O55 with the required sensitivity and specificity, and the test is validated, the technique will be ready for operational use on field samples.

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