Which exotoxin produced by Staphylococcus aureus is responsible for the formation of bullae in bullous impetigo?

Question

Accepted Answer

B. Exfoliative toxin (ETA/ETB). ## Exotoxins in Staphylococcal Skin Infections

**Key Point:** Exfoliative toxins (ETA and ETB) are serine proteases that cleave desmoglein-1 in the granular layer of the epidermis, causing intraepidermal acantholysis and blister formation characteristic of bullous impetigo.

### Mechanism of Bullae Formation

Exfoliative toxins target **desmoglein-1** (a desmosomal adhesion protein), leading to:
- Loss of cell-to-cell adhesion in the granular layer
- Intraepidermal blister formation (subcorneal)
- Flaccid bullae that rupture easily

### Other Staphylococcal Toxins and Their Roles

| Toxin | Mechanism | Clinical Manifestation |
|-------|-----------|------------------------|
| **Exfoliative toxin (ETA/ETB)** | Serine protease; cleaves desmoglein-1 | Bullous impetigo, staphylococcal scalded skin syndrome (SSSS) |
| **Alpha-hemolysin** | Pore-forming toxin; lyses RBCs and WBCs | Non-bullous impetigo, cellulitis |
| **Panton-Valentine leukocidin (PVL)** | Bi-component toxin; kills neutrophils | Severe skin infections, abscesses, necrotizing pneumonia |
| **TSST-1** | Superantigen; triggers massive T-cell activation | Toxic shock syndrome, scarlet fever-like rash |

**High-Yield:** Bullous impetigo = exfoliative toxin; non-bullous impetigo = alpha-hemolysin and other proteases.

**Clinical Pearl:** Bullous impetigo presents with large, flaccid bullae that rupture easily, leaving a thin, varnish-like crust. Non-bullous impetigo (more common, ~70% of cases) presents with honey-crusted lesions without preceding bullae.

![Impetigo and Staphylococcal Skin Infections diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/3223.webp)

Answer

A. Toxic shock syndrome toxin-1 (TSST-1)

Answer

C. Panton-Valentine leukocidin (PVL)

Answer

D. Alpha-hemolysin

Which exotoxin produced by Staphylococcus aureus is responsible for the formation of bullae in bullous impetigo?

Explanation

Exotoxins in Staphylococcal Skin Infections

Mechanism of Bullae Formation

Other Staphylococcal Toxins and Their Roles

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Toxin	Mechanism	Clinical Manifestation
Exfoliative toxin (ETA/ETB)	Serine protease; cleaves desmoglein-1	Bullous impetigo, staphylococcal scalded skin syndrome (SSSS)
Alpha-hemolysin	Pore-forming toxin; lyses RBCs and WBCs	Non-bullous impetigo, cellulitis
Panton-Valentine leukocidin (PVL)	Bi-component toxin; kills neutrophils	Severe skin infections, abscesses, necrotizing pneumonia
TSST-1	Superantigen; triggers massive T-cell activation	Toxic shock syndrome, scarlet fever-like rash