Fungal, Bacterial, and Viral Infections of the Skin

Abstract

The skin can become infected by viruses, fungi, and bacteria, including some that ordinarily are harmless colonizing organisms. The most common fungal infections are caused by dermatophytes, which can involve the hair, nails, and skin. Potassium hydroxide (KOH) preparations of specimens from affected areas typically demonstrate hyphae, and either topical or systemic antifungal therapy usually cures or controls the process. The most common bacterial pathogens are Staphylococcus aureus and group A streptococci, which, alone or together, can cause a wide variety of disorders, including impetigo, ecthyma, and cellulitis. Topical antibiotics may suffice for impetigo, but ecthyma and cellulitis require systemic treatment. S. aureus, including methicillin-resistant strains, can also cause furuncles, carbuncles, and cutaneous abscesses. For these infections, incision and drainage without antibiotics are usually curative. Warts are the most common cutaneous viral infection, and eradication can be difficult, especially where the skin is thick, such as the palms and soles, or the patient is immunocompromised. Most therapies consist of trying to destroy the viruses by mechanical, chemical, or immune mechanisms. This review covers dermatophyte infections, yeast infections, bacterial infections, and viral infections of the skin. Figures show the classic annular lesion of tinea corporis, a typical kerion presenting as a zoophilic Microsporum canis infection of the scalp (tinea capitis), tinea corporis, tinea barbae, tinea pedis between and under the toes and on the plantar surface, inflammatory tinea pedis, tinea unguium, tinea manuum, angular cheilitis, prominent satellite lesions of discrete vesicles associated with candidiasis, facial candidiasis, Candida paronychia, tinea versicolor, nonbullous impetigo, bullous impetigo, ecthyma, leg cellulitis, erythema and edema on the cheeks, eyelids, and nose, furuncle, carbuncle, nasal folliculitis, pitted keratolysis, trichomycosis axillaris, necrotizing fasciitis, Fournier gangrene, folliculitis, plantar wart, condyloma acuminatum, and benign lesions of bowenoid papulosis. Tables list dermatophyte species, terminology of dermatophyte infections, topical agents for dermatophyte infections, treatment options for impetigo (adult doses), and treatment options for erythrasma. This review contains 29 figures, 12 tables, and 36 references Keywords: Staphylococcus aureus, methicillin-resistant strains, furuncles, carbuncles, cutaneous abscesses, dermatophytes, zoophilic Microsporum canis, andidiasis, facial candidiasis, Candida paronychia, tinea versicolor, nonbullous impetigo, bullous impetigo, ecthyma, leg cellulitis, erythema