Escherichia Coli And Other Enterobacteriaceae Infections

Enterobacteriaceae - a family of mostly aerobic, gram­negative bacilli - cause local and systemic infections, including an invasive diarrhea that resembles shigellosis and, more often, a noninvasive, toxin-mediated diarrhea that resembles cholera. With other bacilli of this family, Escherichia coli causes most nosocomial infections. Noninvasive, enterotoxin-producing E. coli infections may be a major cause of diarrhea 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 the risk of death may be quite high.

Causes

Although some strains of E. coli exist as part of the normal GI flora, infection usually comes from nonindigenous strains. For example, noninvasive diarrhea results from two toxins produced by enterotoxigenic or enteropathogenic strains of 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 by contact with contaminated utensils. Incubation takes 12 to 72 hours.

Signs and symptoms

An E. coli infection can make a person very ill. The following are some of the most common symptoms associated with E. coli. However, each individual may experience symptoms differently, and some individuals may have no symptoms at all. Symptoms may include:

• severe bloody diarrhea or non-bloody diarrhea
• severe abdominal cramps

The symptoms of an E. coli infection may resemble other medical conditions. Always consult your physician for a diagnosis.

Diagnostic tests

Because certain strains showing E. coli normally reside in the GI tract, culturing is of little value. However, blood cultures of E. coli point to systemic infection.

A firm diagnosis requires sophisticated identification procedures, such as bioassays. which are expensive, time-consuming and, consequently, not widely available. Diagnosis must rule out salmonella infection and shigellosis, other common infections that produce similar signs and symptoms.

Treatment

Appropriate treatment consists of enteric precautions, correction of fluid and electrolyte imbalances and, in an infant or immunocompromised patient, I.V. antibiotics based on the organism's drug sensitivity. For severe diarrhea that poses a risk of dehydration, bismuth sub salicylate or tincture of opium may be ordered.

Prevention

• Avoid swallowing lake or pool water while swimming.
• Wash hands thoroughly after using the toilet.
• Consume only pasteurized milk and milk products. Avoid raw milk.
• Consume only pasteurized juices and ciders.