A 5-year-old boy presented with pyogenic abscess, runny nose, oral thrush & rash on perineal areas. On culturing pus Staphylococcus aureus was isolated. A test was performed whose finding is shown below. Which of the following is the most likely gene involved in the above condition: –

**Core Concept**
The question is testing the student's understanding of Staphylococcus aureus pathogenicity and the genetic basis of a specific condition associated with this bacterium.

**Why the Correct Answer is Right**
The condition described, characterized by pyogenic abscess, runny nose, oral thrush, and rash on perineal areas, is suggestive of staphylococcal scalded skin syndrome (SSSS). This condition is caused by the production of exfoliative toxins by Staphylococcus aureus. The exfoliative toxins are encoded by the *epidermolytic toxin A (eta)* or *epidermolytic toxin B (etb)* genes. The test result likely shows the presence of these genes, making it a key factor in the diagnosis of SSSS. The correct answer is the gene responsible for encoding exfoliative toxins.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the gene responsible for encoding exfoliative toxins is not mentioned. While it might be a gene involved in SSSS, it is not the correct answer.
* **Option B:** This option is incorrect because it is a different gene that is not directly related to the production of exfoliative toxins in SSSS.
* **Option C:** This option is incorrect because it is also a different gene that is not directly related to the production of exfoliative toxins in SSSS.

**Clinical Pearl / High-Yield Fact**
Staphylococcal scalded skin syndrome is a condition that affects infants and young children, characterized by a distinctive peeling skin rash. It is caused by the production of exfoliative toxins by Staphylococcus aureus, which cleaves desmoglein 1, a component of the epidermal cell-cell adhesion complex.

**Correct Answer:** D. **eta**

✓ Correct Answer: B. PHOX