The Enterobacteriaceae — a group of mostly aerobic, gram-negative bacilli — cause local and systemic infections, including an invasive diarrhea resembling shigella and, more commonly, a noninvasive toxin-mediated diarrhea resembling cholera. With other Enterobacteriaceae, Escherichia coli causes most nosocomial infections. Noninvasive, enterotoxin-producing E. coli infections may be a major cause of diarrheal illness in children in the United States. (See Enterobacterial infections.)
The prognosis in mild to moderate infection is good. Severe infection requires immediate fluid and electrolyte replacement to avoid fatal dehydration, especially among children, in whom mortality may be quite high.
Although some strains of E. coli exist as part of the normal GI flora, infection usually results from certain nonindigenous strains. For example, noninvasive diarrhea results from two toxins produced by strains called enterotoxic or enteropathogenic E. coli. Enteropathogenic E. coli serotype 0157:H7 is the most well-known strain in the United States. These toxins interact with intestinal juices and promote excessive loss of chloride and water. In the invasive form, E. coli directly invades the intestinal mucosa without producing enterotoxins, thereby causing local irritation, inflammation, and diarrhea. Normal strains can cause infection in immunocompromised patients.
Transmission can occur directly from an infected person or indirectly by ingestion of contaminated food or water or contact with contaminated utensils. Incubation takes 12 to 72 hours.
Incidence of E. coli infection is highest among travelers returning from other countries, particularly Mexico, Southeast Asia, and South America. E. coli infection also induces other diseases, especially in people whose resistance is low. The strain E. coli 0157:H7 has been associated with undercooked hamburger and with animals and petting zoos.
Effects of noninvasive diarrhea depend on the causative toxin but may include the abrupt onset of watery diarrhea with cramping abdominal pain and, in severe illness, acidosis. Invasive infection produces chills, abdominal cramps, and diarrheal stools containing blood and pus.
Infantile diarrhea from an E. coli infection is usually noninvasive; it begins with loose, watery stools that change from yellow to green and contain little mucus or blood. Vomiting, listlessness, irritability, and anorexia commonly precede diarrhea. This condition can progress to fever, severe dehydration, acidosis, and shock. Bloody diarrhea may occur from infection with E. coli 0157:H7, which has also been associated with hemolytic uremic syndrome in children.
Because certain strains of E. coli normally reside in the GI tract, culturing is of little value; a working diagnosis depends on clinical observation. However, if E. coli 0157:H7 is suspected, notify the laboratory so that appropriate testing of stool specimens can be performed.
A firm diagnosis requires sophisticated identification procedures, such as bioassays, that are expensive, time-consuming and, consequently, not widely available. Diagnosis must rule out salmonellosis and shigellosis, other common infections that produce similar signs and symptoms.
Treatment consists of correction of fluid and electrolyte imbalances; for an infant or immunocompromised patient, I.V. antibiotics based on the organism's drug sensitivity; and salicylates or opium tincture for cramping and diarrhea.
❑Keep accurate intake and output records. Measure stool volume and note the presence of blood or pus. Replace fluids and electrolytes as needed, monitoring for decreased serum sodium and chloride levels and signs of gram-negative shock. Watch for signs of dehydration, such as poor skin turgor and dry mouth.
❑For infants, use contact precautions, give nothing by mouth, administer antibiotics as ordered, and maintain body warmth.
To prevent spread of this infection:
❑Prevent direct patient contact during epidemics. Report cases to local public health authorities. E. coli 0157:H7 is a reportable disease.
❑Use proper hand-hygiene technique. Teach health care personnel, patients, and their families to do the same.
❑Follow standard precautions. Provide the patient with a private room, wear protective clothing as necessary, such as when handling feces or soiled linens, and perform scrupulous hand hygiene before entering and after leaving the patient's room.
❑Advise travelers to foreign countries to avoid unbottled water and uncooked fruits and vegetables.
Review other book chapters online related to Enterotoxigenic Escherichia coli:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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