Paronychia: The Daily PANCE Blueprint

The answer is Staphylococcus aureus

This patient presents with classic signs of acute paronychia, which is an infection of the nail fold. Staphylococcus aureus is the most common causative organism in acute paronychia, particularly in cases associated with nail biting or finger trauma. The acute onset with erythema, pain, and swelling are characteristic of bacterial infection rather than fungal etiology. S. aureus produces various virulence factors that contribute to the inflammatory response seen in this condition. Treatment typically involves warm compresses, topical or oral antibiotics with coverage for gram-positive organisms, and in some cases, incision and drainage if an abscess has formed.

• Pseudomonas aeruginosa typically causes green discoloration of the nail plate and is often associated with prolonged exposure to water (e.g., dishwashers, swimmers). This history and the clinical presentation don’t suggest Pseudomonas infection.
• Trichophyton rubrum is a dermatophyte that causes onychomycosis (fungal nail infection). It presents with gradual nail plate changes including discoloration, thickening, and brittleness rather than acute inflammation of the nail fold.
• Candida albicans can cause chronic paronychia, which presents with less acute symptoms and is more common in people with frequent water exposure, diabetes, or immunosuppression. The acute presentation in this case is more consistent with bacterial infection.
• Streptococcus pyogenes can cause nail fold infections but is less common than S. aureus in typical paronychia. Streptococcal infections often present with more diffuse erythema and less purulent discharge compared to staphylococcal infections.