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The Serodiagnosis of Infections Caused by Verocytotoxin-Producing Escherichia coli Based on Salivary Antibodies to E. coli Lipopolysaccharide (LPS)

Institutions
Health Protection Agency
Start date
2001
End date
2003
Objective
The aim of the project was to investigate the possibility of using samples of saliva and avoid the need to use samples of blood.

A commercial sampling kit (Oracol©) was used to obtain saliva from patients, and involved a sponge on a stick placed within a plastic transport tube.

Antibodies to E. coli O157 were detected in patients' saliva; however, the levels of these antibodies and how long they persist in a patient are unknown.

It was hoped that the project would provide information about the sensitivity and specificity of the antibody tests. Due to the ease of sampling a patient, it was also intended to provide knowledge of when the levels of salivary antibodies were at their highest during the disease process, so that the times when patients should be sampled can be optimised.

By routine E. coli O157 antibody testing using samples of blood, patients can be identified as having antibodies to E. coli O157. These patients were contacted and supplied with saliva sampling kits and requested to submit samples of saliva for research purposes.

In anticipation of putative cases of infection with O157, the ten laboratories, which had the highest incidence of antibody-positive patients for a given year, were targeted and equipped with saliva sampling kits and documentation enabling patients/parents to provide their permission for their samples of saliva to be used for the study.

More information
The project relates to human disease caused by a form of enteric bacterium called Escherichia coli (E. coli) which produces a poison (toxin) called 'Verocytotoxin' and these Verocytotoxin-producing E. coli make up a family of bacteria termed - VTEC.

Strains of E. coli can be 'typed' based on various bacterial properties and one particular form of VTEC, called O157 (E. coli O157), has been shown to be a cause of serious illness with symptoms including haemolytic uraemic syndrome (HUS).

People are diagnosed as being infected with E. coli O157 or other VTEC following the culture of these bacteria from patients' faeces. In the absence of faecal VTEC, a precise diagnosis cannot be made.

Patients infected with E. coli O157 respond to infection by activating their immune system. One of the responses is the production of molecules called antibodies, which appear in the patients' blood during disease and may persist for several months.

These antibody molecules are specifically designed to attach to the E. coli O157 causing them to clump together, making it easier for the immune system to clear these bacteria from the body.

These antibody molecules are highly specific for E. coli O157 and can be used to provide evidence that a person has been infected with E. coli O157, by screening the patient's blood for antibodies which bind to the E. coli O157. This procedure has been shown to be highly sensitive and forms the basis of a routine laboratory test.

Infections with E. coli O157 occur more frequently in young children and infants, and with the aim of avoiding the need to take a blood sample from these patients, other body fluids were considered as a source of antibodies. Initial studies have demonstrated that a patient's saliva may also contain antibody molecules that bind to E. coli O157, but the incidence of these antibodies and the levels at which they occur during disease are not known.

The present project was designed to obtain a better understanding of these salivary antibodies, which bind to E. coli O157 and VTEC, and how they can be used for diagnosis of infections caused by these bacteria.

Find more about this project and other FSA food safety-related projects at the Food Standards Agency Research webpage.

Final report is available from the FSA Library and Information centre.

To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency ( Tel: 020 7276 8181/8182 or by e-mail to: library&info@foodstandards.gsi.gov.uk ).

Funding Source
Food Standards Agency
Project number
B11008
Categories
Escherichia coli