Acute Bloody Diarrhoea and Shiga Toxin Escherichia coli
(May 2005)
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Acute Bloody Diarrhoea and Shiga Toxin Escherichia coli.pdf)
Why is detection of Escherichia coli (STEC) important?
A 14-year-od girl presented to a general practitioner with a 5-day history of bloody diarrhoea. She was investigated with colonoscopy and biopsies were consistent with an acute self-limiting colitis. However, an inflammatory bowel disease could not be excluded. STEC was detected by PCR (see below), providing confirmation of the cause of her illness and considerable reassurance to both clinicians and the patient. She luckily recovered fully over the next week and did not develop haemolytic uraemic syndrome (HUS).
The detection of STEC also allows the Population Health Unit to identify possible clusters of infection related to food or other sources, which may lead to preventative action.
What is STEC?
Shiga toxin producing I is the commonest cause of post-diarrhoeal HUS in industrialised countries, including Australia. The majority of STEC infections are acquired by humans via the food chain, particularly from contaminated meat sources. Patients with STEC infection may develop gastroenteritis or an acute haemorrhagic colitis that is self-limited. Between 5 and 15% of infected patients develop HUS 3-10 days after the primary infection. Children less than 5 years of age are at greatest risk of developing disease. HUS is thought to result from widespread endothelial damage that occurs in small vessels within the kidney and elsewhere. This results in mechanical damage to red cells with resultant haemolysis and renal failure.
How is STEC testing performed?
The Hunter Area Pathology Service routinely screens for STEC in all stool samples with profuse red blood cells, from which no usual bacterial diarrhoeal pathogen is detected. Stool samples from HUS cases are also screened. The screening method is a molecular polymerase chain reaction (PCR) method that directly detects either of the toxigenic genes, stx1 or stx2 that are carried by STEC strains of E. coli.
How frequent is STEC infection detected in the Hunter?
Our screening results were recently published in the Communicable Disease Intelligence journal (Commun. Dis. Intell. 2004;28:390-391, available on the Internet). Four of 126 Hunter patients were positive for the STEC toxin genes by PCR (3.2%). These results were similar to South Australian findings where 139 of 5,829 patients were positive for STEC toxin genes (2.4%). Two cases of HUS positive for STEC were reported from the Hunter, a 26-month-old male and a 62-year-old male.
What is the implication of a positive STEC screening PCR test?
How frequent is STEC infection detected in the Hunter?
Our screening results were recently published in the Communicable Disease Intelligence journal (Commun. Dis. Intell. 2004;28:390-391, available on the Internet). Four of 126 Hunter patients were positive for the STEC toxin genes by PCR (3.2%). These results were similar to South Australian findings where 139 of 5,829 patients were positive for STEC toxin genes (2.4%). Two cases of HUS positive for STEC were reported from the Hunter, a 26-month-old male and a 62-year-old male.
Do all pathology providers perform STEC screening on bloody stools?
Other pathology providers do not routinely perform STEC testing. They will do this upon request. In general, stool cultures only detect pathogenic Campylobacter, Shigella and Salmonella species and STEC can only be detected through special procedures such as PCR.
About the Author
This HAPS Communique was written by Dr John Ferguson (Clinical Microbiologist & Infectious Diseases Physician).
If you have any questions regarding this topic Dr Ferguson and Microbiology can be contacted on Telephone: (02) 49214000, Facsimile: (02) 49214400.