Enterobacteriaceae — a group of mostly aerobic gram-negative bacilli — cause local and systemic infections, including an invasive diarrhea that resembles shigella and, more commonly, a noninvasive toxin-mediated diarrhea that resembles cholera.
Escherichia coli and other Enterobacteriaceae cause most nosocomial infections. Noninvasive, enterotoxin-producing E. coli infections may be a major cause of diarrheal illness in children in the United States.
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. 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.
The incidence of E. coli infection is highest among travelers returning from other countries, particularly Mexico and those in Southeast Asia and South America. E. coli infection also induces other diseases, especially in people whose resistance is low. Another strain, E. coli 0157:H7, has been reported. It’s associated with undercooked hamburger and produces hemorrhagic colitis and hemolytic uremic syndrome in children, a principal cause of acute kidney failure in children.
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 that contain 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 an E. coli 0157:H7 infection.
Because certain strains of E. coli normally reside in the GI tract, culturing is of little value; a working diagnosis depends on clinical observation alone.
A firm diagnosis requires such sophisticated identification procedures as bioassays, which are expensive, time-consuming and, consequently, not widely available. The diagnosis must rule out salmonellosis and shigellosis, other common infections that produce similar signs and symptoms.
Effective treatment consists of isolation and correction of fluid and electrolyte imbalance. Antibiotics haven’t been shown to improve the course of the disease and may precipitate kidney complications. For cramping and diarrhea, bismuth subsalicylate may be given; antidiarrheals, such as loperamide, should be avoided.
❑ Keep accurate intake and output records. Measure stool volume, and note the presence of blood and 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.
To prevent the spread of this infection:
❑ Screen all hospital personnel and visitors for diarrhea, and prevent them from making direct patient contact during epidemics.
CLINICAL TIP: Report cases to the local public health authorities.
❑ Use standard precautions: private room, gown and gloves while handling feces, and hand washing before entering and after leaving the patient’s room.
❑ To prevent the accumulation of these water-loving organisms, discard suction bottles, irrigating fluid, and open bottles of saline solution every 24 hours. Be sure to change I.V. tubing according to facility policy and empty the ventilator water reservoirs before refilling them with sterile water. Remember to use suction catheters only once.
❑ Advise travelers to foreign countries to avoid unbottled water and uncooked vegetables.
❑ Consumers can prevent E. coli 0157:H7 infection by thoroughly cooking ground beef (to 160° F [71.1° C] on a food thermometer), avoiding unpasteurized milk, and washing hands thoroughly.
Review other book chapters online related to Bacteremia:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2003 ISBN: 1-58255-266-5 
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