## Virulence Factors of ETEC **Key Point:** ETEC causes watery diarrhea through enterotoxin production and adhesion factors, NOT through Shiga toxin. ### ETEC Pathogenic Mechanisms | Virulence Factor | Mechanism | Effect | | --- | --- | --- | | Heat-labile toxin (LT) | ADP-ribosylates Gs protein → ↑ cAMP | Secretory diarrhea | | Heat-stable toxin (ST) | Activates guanylyl cyclase → ↑ cGMP | Secretory diarrhea | | Colonization Factor Antigen (CFA) | Fimbrial adhesin | Mucosal attachment | | Shiga toxin | Inactivates 60S ribosome | **Produced by STEC, NOT ETEC** | **High-Yield:** ETEC = **Enterotoxin** + **Adhesin**. The toxins cause secretory (watery) diarrhea without mucosal invasion or bloody stools. ### Clinical Distinction - **ETEC:** Traveler's diarrhea; watery stools; no blood/mucus; self-limited (3–5 days) - **STEC (Shiga toxin-producing E. coli):** Hemorrhagic colitis; bloody diarrhea; risk of HUS; toxin-mediated injury **Warning:** Do NOT confuse ETEC with STEC (O157:H7). Shiga toxin is the hallmark of STEC, not ETEC.
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