Why hasn't this tender lesion responded to antibiotic?

Case 2:
A tender, crusting eruption first arose on a 69-year-old man’s ear 10 days earlier; an antibiotic failed to clear the lesion. The patient is otherwise healthy, with no predisposing diseases or history of trauma.

Why hasn't this tender lesion responded to an antibiotic?
    A. Actinic keratosis.
    B. Impetigo.
    C. Candidiasis.
    D. Squamous cell carcinoma.
    E. Inflamed seborrheic keratosis.

Answer on next page

A fungal culture that grew Candida albicans confirmed candidiasis, C. Consider candidiasis in patients who do not respond to antibiotic therapy for suspected impetigo; a candidal infection can mimic the bacterial disease. This patient’s lesion resolved after short-term oral antifungal therapy. In contrast to the rapid eruption of this patient’s lesion, actinic keratosis, squamous cell carcinoma, and seborrheic keratosis grow slowly.