A person returns to Delhi from Bangladesh after 2 days and has diarrhoes. Stool examination shows RBC’s in stool. The likely organism causing is ?
**Core Concept**
The question is testing the knowledge of infectious agents that cause gastrointestinal symptoms, particularly those associated with travel to certain regions. The presence of **red blood cells (RBCs)** in the stool suggests an invasive intestinal infection.
**Why the Correct Answer is Right**
Given the travel history to Bangladesh and the symptom of diarrhea with RBCs in the stool, the likely cause is an infection by a pathogen common in that region. **Entamoeba histolytica** is a common cause of dysentery (diarrhea with blood and mucus) in travelers to endemic areas, including Bangladesh.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while it could cause diarrhea, it is less commonly associated with RBCs in the stool in the context provided.
**Option B:** Incorrect as it typically causes a non-bloody diarrhea.
**Option C:** Incorrect because, although it can cause bloody diarrhea, the context of travel to Bangladesh makes **Entamoeba histolytica** more likely.
**Clinical Pearl / High-Yield Fact**
Remember that the presence of RBCs in the stool narrows the differential diagnosis towards invasive pathogens like **Entamoeba histolytica**, especially in travelers to endemic areas.
**Correct Answer:** D. Entamoeba histolytica