At least five distinct pathotypes of intestinal pathogenic E. coli exist; see Chap. 82. Infectious Diarrheas for more details. As mentioned above, these strains are rarely encountered as part of the commensal flora in healthy individuals.
- Shiga toxin-producing E. coli (STEC)/enterohemorrhagic E. coli (EHEC)/Shiga toxin-producing enteroaggregregative E. coli (STEAEC): In addition to diarrhea, STEC/EHEC infection results in the hemolytic-uremic syndrome (HUS) in 2-8% of pts, particularly those who are very young or elderly. STEAEC results in a higher rate of HUS (~20%), with a higher incidence among adults, especially young women.
- - STEC/EHEC/STEAEC is associated with ingestion of contaminated food (e.g., undercooked ground beef, fresh produce) and water; person-to-person transmission (e.g., at day-care centers) is an important route for secondary spread.
- - Disease can be caused by <102 colony-forming units (CFUs) of STEC/EHEC/STEAEC.
- - In contrast to the other pathotypes, STEC/EHEC/STEAEC (including E. coli O157:H7) causes infection more frequently in industrialized countries than in developing countries.
- Enterotoxigenic E. coli (ETEC): These strains are a major cause of endemic diarrhea among children residing in tropical and low-income countries and are the most common agent of traveler's diarrhea; 106-1010 CFU are needed to cause disease.
- Enteropathogenic E. coli (EPEC): EPEC is an important cause of diarrhea among infants in developing countries.
- Enteroinvasive E. coli (EIEC): EIEC, an uncommon cause of diarrhea, produces inflammatory colitis (stools containing mucus, blood, and inflammatory cells) similar to that caused by Shigella and primarily affects children and travelers in developing countries; 108-1010 CFU are needed to cause disease.
- Enteroaggregative and diffusely adherent E. coli (EAEC): EAEC was initially described in young children in developing countries. More recent studies indicate that EAEC may be a common cause of prolonged, watery diarrhea in all age groups in industrialized countries.