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Enterovirulent Escherichia coli EEC

E. coli are bacteria belonging the family Enterobacteriaceae. E. coli is a normal inhabitant of the intestines of all animals, including humans however some types cause disease. 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.

There are 4 classes of enterovirulent E. coli (collectively referred to as the EEC group) that cause gastroenteritis in humans.

 

Enterotoxigenic Escherichia coli (ETEC)

First, the enterotoxigenic (ETEC) strains. They cause diarrhea in infants in developing countries and in travelers. Gastroenteritis is the common name of this disease although it is also frequently called travelers' diarrhea. Common symptoms include watery diarrhea, abdominal cramps, nausea and malaise.

Water contamination with human sewage contaminates foods. As well as infected food handlers. These organisms are in dairy products such as semi-soft cheeses.

MMWR 43(5):1994

 

Enteropathogenic Escherichia coli (EPEC)

Secondly, the enteropathogenic (EPEC) strains are defined as E. coli belonging to serogroups epidemiological implicated as pathogens but whose virulence mechanism is unrelated to the excretion of typical E. coli enterotoxins.

Food borne outbreaks are sporadic. Humans, cows, and pigs can be infected.

Infantile diarrhea is the name of the disease usually associated with EPEC

EPEC cause either a watery or bloody diarrhea. Bloody diarrhea is associated with bacteria attachment and possibly a toxin similar to that of Shigella

EPEC are highly infectious for infants.

Occasionally, infant diarrhea is prolonged, leading to dehydration, electrolyte imbalance and death.

 

Escherichia coli O157:H7

Thirdly, the enterohemorrhagic (EHEC) strain designated E. coli O157:H7.

E. coli serotype O157:H7 that produces large quantities of one or more toxins that cause severe damage to the lining of the intestine. These toxins [verotoxin (VT), shiga-like toxin] are closely related or identical to the toxin produced by Shigella.

Hemorrhagic colitis is the name of the acute disease caused by E. coli O157:H7 (also called "hamburger disease")

 

Disease is characterized by cramping abdominal pain and diarrhea, which is watery but becomes bloody. Occasionally vomiting occurs. Fever is either low-grade or absent. The illness is usually self-limited and lasts for an average of 8 days. Some individuals have watery diarrhea only.

Hemorrhagic colitis is found by identification of E. coli of serotype O157:H7 or other verotoxin-producing E. coli from diarrheal stools. Alternatively, the stools can be tested directly for the presence of verotoxin. Confirmation can be obtained by isolating of E. coli of the same serotype from the incriminated food.

 

Undercooked or raw hamburger (ground beef) has been implicated in many outbreaks, as well as alfalfa sprouts, unpasteurized fruit juices, dry-cured salami, lettuce, game meat, raw milk and cheese curds.

 

 

Some, particularly the very young, develop hemolytic uremic syndrome (HUS), characterized by renal failure and hemolytic anemia. From 0 to 15% of hemorrhagic colitis victims develop HUS with loss of kidney function.

Other complications particularly in the elderly involve HUS, with two other symptoms, fever and neurological symptoms, constitutes thrombotic thrombocytopenic purpura (TTP).

Sorbitol-MacConkey agar has been used extensively to isolate this organism.. Rapid methods using a variety of technologies, including recombinant DNA methods, are being developed.

References: MMWR 45(30):1996, MMWR 49(15):2000 , MMWR 48(36):1999

 

Enteroinvasive Escherichia coli(EIEC)

Fourthly are the enteroinvasive (EIEC) strains.cause a form of bacillary dysentery. Enteroinvasive E. coli (EIEC) causes bacillary dysentery. The EIEC strains responsible for this syndrome are similar to Shigella spp. The EIEC invade the intestine, causing dysentery, with blood and mucus in the stools of infected individuals. Any food contaminated with human feces from an ill individual, could spread disease. Outbreaks have been associated with hamburger meat and unpasteurized milk.

Dysentery caused by EIEC occurs within 12 to 72 hours after eating contaminated food. With abdominal cramps, diarrhea, vomiting, fever, chills, and generalized malaise. Dysentery is generally self-limiting but cases of hemolytic uremic syndrome (HUS) could develop.

Foods and stool cultures are examined .Detection of this organism in foods is extremely difficult.