A 6-year-old child presents with multiple honey-colored crusted lesions on the face and around the nose. Gram stain of exudate shows Gram-positive cocci in clusters. A few lesions have large bullae. The MOST common causative organisms are:
- A Staphylococcus aureus (non-bullous and bullous) and Streptococcus pyogenes (non-bullous) ✓
- B Streptococcus pyogenes only
- C Staphylococcus epidermidis and S. aureus
- D Pseudomonas aeruginosa in bullous form only
Explanation
Impetigo has two clinical forms: non-bullous (most common; ~70%) and bullous. Non-bullous impetigo is caused by Staphylococcus aureus, Streptococcus pyogenes (Group A Strep), or both; it produces the classic honey-colored crusted lesion from rupture of thin-walled vesicles/pustules. Bullous impetigo is caused exclusively by S. aureus (phage group II, notably ST-1) producing exfoliative toxins (ETs) A and B that cleave desmoglein-1 in the superficial epidermis, producing flaccid bullae. The co-existence of both forms in this child confirms S. aureus as the primary pathogen, with GAS also contributing to the non-bullous component. Staphylococcus epidermidis and Pseudomonas do not cause impetigo.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.