A 20 year old male had pain abdomen and mild fever followed by gastroenteritis. The stool examination showed presence of pus cells and RBCs on microscopy. The etiological agent responsible is most likely to be:-
**Core Concept**
In this scenario, the presence of pus cells and RBCs in the stool indicates an invasive bacterial infection of the gastrointestinal tract, leading to inflammation and tissue damage. The etiological agent responsible is likely to be a bacterium that can cause enteric fever, a condition characterized by fever, abdominal pain, and gastrointestinal symptoms.
**Why the Correct Answer is Right**
The presence of pus cells and RBCs in the stool suggests a bacterial infection that has caused damage to the intestinal mucosa. Enteric fever, caused by Salmonella Typhi and Salmonella Paratyphi, is characterized by invasion of the intestinal epithelial cells, leading to inflammation and tissue damage. The bacteria can cause the release of inflammatory mediators, which leads to the presence of pus cells and RBCs in the stool. The bacteria also have a mechanism to evade the host's immune response, which allows them to cause a prolonged infection.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the presence of pus cells and RBCs in the stool is not a characteristic feature of viral gastroenteritis. Viral infections typically cause a self-limiting illness with minimal inflammation.
* **Option B:** This option is incorrect because Shigella dysenteriae is a cause of dysentery, but it is not the most likely cause of enteric fever. Shigella infections typically cause a more acute presentation with severe diarrhea and abdominal pain.
* **Option D:** This option is incorrect because Campylobacter jejuni is a common cause of bacterial gastroenteritis, but it is not typically associated with the presence of pus cells and RBCs in the stool.
**Clinical Pearl / High-Yield Fact**
The presence of pus cells and RBCs in the stool in a patient with enteric fever is a red flag for invasive bacterial infection. This finding can help differentiate enteric fever from other causes of gastroenteritis, such as viral infections.
**Correct Answer: B. Shigella dysenteriae.**