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Escherichia coli ETEC

General characteristics

E. coli are Gram-negative, rod-shaped bacteria belonging the family Enterobacteriaceae

E. coli is a normal inhabitant of the intestines of all animals, including humans. When aerobic culture methods are used, E. coli is the dominant species found in faeces. Normally E. coli serves a useful function in the body by suppressing the growth of harmful bacterial species and by synthesizing appreciable amounts of vitamins. A minority of E. coli strains are capable of causing human illness by several different mechanisms. Among these are the enterotoxigenic (ETEC) strains. They comprise a relatively small proportion of the species and have been etiologically associated with diarrhoeal illness of all age groups from diverse global locations. The organism frequently causes diarrhoea in infants in less developed countries and in visitors there from industrialized countries. The aetiology of this cholera-like illness has been recognized for about 20 years.

Disease symptoms

Gastroenteritis is the common name of the illness caused by ETEC, although travelers' diarrhoea is a frequent sobriquet.

The most frequent clinical syndrome of infection includes watery diarrhoea, abdominal cramps, low-grade fever, nausea and malaise.

Infective dose--Volunteer feeding studies indicate that a relatively large dose (100 million to 10 billion bacteria) of enterotoxigenic E. coli is probably necessary to establish colonization of the small intestine, where these organisms proliferate and produce toxins, which induce fluid secretion. With high infective dose, diarrhoea can be induced within 24 hours. Infants may require fewer organisms for infection to be established.


During the acute phase of infection, large numbers of enterotoxigenic cells are excreted in faeces. These strains are differentiated from nontoxigenic E. coli present in the bowel by a variety of in vitro immunochemical, tissue culture, or gene probe tests designed to detect either the toxins or genes that encode for these toxins. The diagnosis can be completed in about 3 days.

Associated foods

ETEC is not considered a serious foodborne disease hazard in countries having high sanitary standards and practices. Contamination of water with human sewage may lead to contamination of foods. Infected food handlers may also contaminate foods. These organisms are infrequently isolated from dairy products such as semi-soft cheeses.


Enterobacteria (incl. E.coli ) are heat-sensitive and will be killed by thorough heating (over 70 °C). Raw or undercooked foods and cross-contamination, when cooked material comes into contact with raw produce or contaminated materials (cutting boards), are the main causes of infection. Proper cooking and hygienic food handling thus can prevent enterobacterial infections to a large extend.

Risk populations

Infants and travelers to underdeveloped countries are most at-risk of infection.


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