Which E. coli pathotype is intracellular and characteristically causes bloody diarrhea?

Which E. coli pathotype is intracellular and characteristically causes bloody diarrhea?

• A. ETEC
• B. EAEC
• C. EPEC
• D. EIEC

Answer: (D)

The key idea is distinguishing invasive, inflammatory diarrhea from toxin-driven, noninflammatory diarrhea. Enteroinvasive E. coli is the one that behaves like Shigella: it invades and spreads within colonic epithelial cells, triggering a strong inflammatory response. This intracellular invasion leads to dysentery-like symptoms with abdominal cramps, fever, and bloody or mucousy stool. The invasion of the mucosa, rather than toxin-mediated secretion, is what makes diarrhea inflammatory and bloody. The other E. coli pathotypes cause different patterns: ETEC produces watery, noninflammatory diarrhea via enterotoxins; EAEC forms a biofilm and typically causes persistent watery diarrhea; EPEC attaches to and effaces enterocytes and also tends to cause watery or mild diarrhea, especially in infants. Thus, the combination of intracellular invasion and bloody diarrhea points to the invasive pathotype.

The key idea is distinguishing invasive, inflammatory diarrhea from toxin-driven, noninflammatory diarrhea. Enteroinvasive E. coli is the one that behaves like Shigella: it invades and spreads within colonic epithelial cells, triggering a strong inflammatory response. This intracellular invasion leads to dysentery-like symptoms with abdominal cramps, fever, and bloody or mucousy stool. The invasion of the mucosa, rather than toxin-mediated secretion, is what makes diarrhea inflammatory and bloody.

The other E. coli pathotypes cause different patterns: ETEC produces watery, noninflammatory diarrhea via enterotoxins; EAEC forms a biofilm and typically causes persistent watery diarrhea; EPEC attaches to and effaces enterocytes and also tends to cause watery or mild diarrhea, especially in infants. Thus, the combination of intracellular invasion and bloody diarrhea points to the invasive pathotype.