Bullous impetigo is caused by –
**Core Concept**
Bullous impetigo is a skin infection characterized by the formation of bullae, which are large blisters containing serous or hemorrhagic fluid. This condition is primarily caused by bacterial pathogens that produce exfoliative toxins. The underlying principle being tested is the understanding of the microbiological etiology of bullous impetigo.
**Why the Correct Answer is Right**
The correct answer is related to the bacterium *Staphylococcus aureus*, which is known to produce exfoliative toxins that cause the epidermal splitting and bullae formation seen in bullous impetigo. These toxins, specifically exfoliative toxin A and B, target desmoglein 1, a key component of the desmosomes that hold keratinocytes together in the skin.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although it may be related to other forms of impetigo, it is not the primary cause of bullous impetigo.
**Option B:** Incorrect as it is not typically associated with bullous impetigo.
**Option C:** Incorrect because, while *Streptococcus pyogenes* can cause non-bullous impetigo, it is not the primary cause of the bullous form.
**Clinical Pearl / High-Yield Fact**
Bullous impetigo is highly contagious and often seen in children, emphasizing the need for prompt diagnosis and treatment to prevent spread. The presence of bullae is a key distinguishing feature from other forms of impetigo.
**Correct Answer:** D. Staphylococcus aureus.