New E.coli tests on the cards

Related tags E. coli Escherichia coli

New tests that slice off the time taken to identify dangerous
strains of the harmful bacteria Escherichia coli are the
focus of new research from US government scientists.

Agricultural Research Service (ARS) microbiologist Pina Fratamico, at the agency's Eastern Regional Research Center ( ERRC), is working with Pennsylvania state university to develop tests that quickly identify E. coli​ strains.

Sixty-one deaths and 73,000 illnesses are blamed on eating foods contaminated with E. coli​ each year, according to the Centers for Disease Control and Prevention.

Certain E. coli​ strains, such as O157:H7, causes serious diseases, including bloody diarrhea and hemorrhagic colitis. Infections may result in serious health complications, including kidney failure. Other E. coli​ serogroups, including E. coli​ O26, O111 and O121, also cause gastrointestinal illnesses in humans.

Currently, scientists commonly use a procedure called serotyping to distinguish between different types of E. coli​ - some harmful, others harmless. However, this procedure is time-consuming and labour-intensive.

Fratamico, with ERRC's Microbial food safety research unit, and her team are developing both conventional and real-time polymerase chain reaction (PCR) tests. These chemical procedures generate enough of a bacterium's genetic material so that it can be studied and identified. With one real-time PCR reaction, four products can be amplified simultaneously and detected in "real time" as they multiply.

Scientists have little information about some individual E. coli​ serogroups, therefore, the number of diseases these organisms cause is likely underestimated, report the scientists. Fratamico is targeting genes in the E. coli O-antigen gene clusters so researchers can detect and identify specific serogroups and increase knowledge about each one's potency.

In one study, a real-time PCR assay was more sensitive than other detection methods. According to Fratamico, the US department of agriculture's Food Safety and Inspection Service has expressed interest in the new PCR tests for detection and confirmation of E. coli​ O157:H7 and a range of other E. coli​ strains.

In September 2003, the US government reported that the number of ground beef samples tainted with harmful E. coli bacteria had dropped. Inspectors found 0.32 per cent of 4,432 samples of hamburger meat tested positive for E. coli from January to August this year, said Elsa Murano, the Agriculture department's undersecretary for food safety. That compares with 0.78 per cent for the same period in 2002 and 0.84 per cent in 2001. The agency has been testing 7,000 samples each year since 2001.

Related topics Food safety and labeling

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