A 20 year old male had pain in 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**
The underlying principle being tested is the identification of a common cause of infectious gastroenteritis, characterized by the presence of pus cells and red blood cells (RBCs) in the stool. This condition is often associated with **inflammatory diarrhea**, which can be caused by various **bacterial pathogens**. The presence of **pus cells** and **RBCs** in the stool is indicative of an invasive intestinal infection.
**Why the Correct Answer is Right**
Although the correct answer is not provided, a common cause of gastroenteritis with pus cells and RBCs in the stool is **Shigella** or **Salmonella** species, but given the age and symptoms, another common cause could be **Shiga toxin-producing Escherichia coli (E. coli)** or other **enteroinvasive** or **enterohemorrhagic E. coli**. These pathogens invade the intestinal mucosa, causing an inflammatory response that leads to the presence of **pus cells** and **RBCs** in the stool.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option provided, it's challenging to address why it's incorrect directly.
**Option B:** Similarly, without the specific details of Option B, a precise explanation for its incorrectness cannot be given.
**Option C:** And Option C, lacking specific information, cannot be directly refuted.
**Option D:** The same issue applies to Option D, as the content of these options is not provided.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the presence of **blood** and **pus** in the stool, along with symptoms like abdominal pain and fever, suggests an **invasive bacterial infection** rather than a toxin-mediated process. This distinction is crucial for guiding treatment decisions.
**Correct Answer:** Correct Answer: D. Shigella.