3.22 Escherichia Coli (E. Coli)
Microbiology review for the USMLE Step 1 Exam
Esherichia coli (E. coli) is a lactose-fermenting, gram-negative rod causing various diseases, ranging from mild gastroenteritis to septic shock.
E. coli diseases can be divided into two categories: intestinal infections and extraintestinal infections (outside the GI system).
E. coli is part of the normal flora in the human GI tract, but some strains are pathogenic.
Four pathogenic strains of E. coli are Entertoxigenic E. coli (ETEC), Enterohemorrhagic E. coli (EHEC), Enteroinvasive E. coli (EIEC), and Enteropathogenic E. coli (EPEC).
ETEC causes watery diarrhea and is commonly found in food and water in areas with inadequate sanitation and is the most important cause of travelers' diarrhea.
EHEC, also called Shiga toxin-producing E. coli (STEC), causes bloody diarrhea and is associated with contaminated food (spinach, sprouts, lettuce, fruit, undercooked beef).
Shiga toxin produced by EHEC causes cell death in the GI tract and can lead to hemolytic uremic syndrome (HUS) in about 10% of cases.
EIEC causes dysentery-like symptoms such as abdominal pain, fever, and bloody diarrhea.
EPEC causes diarrhea, malnutrition, and growth retardation, especially in children.
Extraintestinal infections include urinary tract infections (UTIs), neonatal sepsis, and pneumonia (incomplete list)
