Escherichia coli O157:H7
|Escherichia coli O157:H7|
|Classification and external resources|
Escherichia coli O157:H7 is an enterohemorrhagic serotype of the bacterium Escherichia coli and a cause of illness, typically through consumption of contaminated food. Infection may lead to hemorrhagic diarrhea, and to kidney failure.
Transmission is via the fecal-oral route, and most illness has been through distribution of contaminated leaf green vegetables.
Strains of E. coli that express shiga-like toxins gained this ability due to infection with a prophage containing the structural coding for the toxin, and nonproducing strains may become infected and produce shiga-like toxins after incubation with shiga toxin positive strains. The prophage responsible seems to have infected the strain's ancestors fairly recently, as viral particles have been observed to replicate in the host if it is stressed in some way (e.g. antibiotics).
United States food advocates have unsuccessfully attempted to control the spread of this illness by promoting the so-called "Kevin's Law". This law would give the United States Department of Agriculture power to shut down food processing plants that fail multiple inspections. The food processing industry vigorously opposes this proposal.
Signs and symptoms
E. coli O157:H7 infection often causes severe, acute hemorrhagic diarrhea (although nonhemorrhagic diarrhea is also possible) and abdominal cramps. Usually little or no fever is present, and the illness resolves in five to 10 days. It can also be asymptomatic.
In some people, particularly children under five years of age and the elderly, the infection can cause hemolytic uremic syndrome (HUS), in which the red blood cells are destroyed and the kidneys fail. About 2–7% of infections lead to this complication. In the United States, HUS is the principal cause of acute kidney failure in children, and most cases of HUS are caused by E. coli O157:H7.
A stool culture can detect the bacterium, although it is not a routine test and so must be specifically requested. The sample is cultured on sorbitol-MacConkey (SMAC) agar, or the variant cefixime potassium tellurite sorbitol-MacConkey agar (CT-SMAC). On SMAC agar O157 colonies appear clear due to their inability to ferment sorbitol, while the colonies of the usual sorbitol-fermenting serotypes of E. coli appear red. Sorbitol nonfermenting colonies are tested for the somatic O157 antigen before being confirmed as E. coli O157. Like all cultures, diagnosis is time-consuming with this method; swifter diagnosis is possible using quick E. coli DNA extraction method plus PCR techniques. Newer technologies using fluorescent and antibody detection are also under development.
E. coli O157:H7 infection is nationally reportable in the USA and Great Britain, and is reportable in most US states. It is also reportable in most states of Australia including Queensland.
While fluid replacement and blood pressure support may be necessary to prevent death from dehydration, most victims recover without treatment in five to 10 days. There is no evidence that antibiotics improve the course of disease, and treatment with antibiotics may precipitate hemolytic uremic syndrome. Antidiarrheal agents, such as loperamide (imodium), should also be avoided as they may prolong the duration of the infection.
The pathogen results in an estimated 2,100 hospitalizations annually in the United States. The illness is often misdiagnosed; therefore, expensive and invasive diagnostic procedures may be performed. Patients who develop HUS often require prolonged hospitalization, dialysis, and long-term followup.
Proper hand washing after using the lavatory or changing a diaper, especially among children or those with diarrhea, reduces the risk of transmission. Anyone with a diarrheal illness should avoid swimming in public pools or lakes, sharing baths with others, and preparing food for others.
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- Food Inc. Directed by Robert Kenner, Independent Films 2009
- Quick E. coli DNA extraction filter paper card
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- "Ban on E. Coli in Ground Beef Is to Extend to 6 More Strains". New York Times. September 12, 2011. Retrieved 2011-10-08. "After the U.S.D.A. banned the O157 form of E. coli from ground beef in 1994, the meat industry sued to block the move, but the agency prevailed in court."
- Haemolytic Uraemic Syndrome Help (HUSH) - a UK Based Charity for Information and Support
- E. coli: Protecting yourself and your family from a sometimes deadly bacterium
- Escherichia coli O157:H7 genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
- For more information about reducing your risk of foodborne illness, visit the US Department of Agriculture's Food Safety and Inspection Service website or the Partnership for Food Safety Education
- Cooking Ground Beef Safely
- briandeer.com, report from The Sunday Times on a UK outbreak, May 17, 1998
- CBS5 report on September 2006 outbreak