E. coli and other Enterobacteriaceae infections
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.