Skin and wound infections: an overview

Author: Michael L. O'Dell
Date: May 15, 1998

The skin has the largest surface area of all of the body organs and is the most exposed organ. Although the skin is remarkably effective in providing protection against the external environment, skin infections are nevertheless a common presentation in most family practices.

Bacterial Skin Infections

Skin infections are often the result of a break in the integrity of the skin. Bacterial skin infections include erythrasma and related diseases, impetigo, ecthyma, folliculitis, erysipelas and cellulitis. While there are certainly other bacterial skin infections, they are either uncommon or result from systemic illness. These types of bacterial skin infections are not discussed in this article.

Erythrasma and Related Conditions

Erythrasma is a superficial skin infection caused by corynebacteria that commonly occurs in intertriginous spaces. While moderate itching and discomfort may be noted, the patient generally presents with only skin-color changes in the infected area. The infected skin is often reddish-brown, may be slightly raised from the surrounding skin and may show the appearance of central clearing. The lesions are largely confluent but may have poorly defined borders. Because of the production of porphyrins by the infecting Corynebacterium, Wood's light demonstrates the lesions as a coral-pink color.

Erythrasma is often confused with a fungal infection, such as tinea cruris, but this confusion is of little consequence since corynebacteria are often eradicated with an imidazole cream (such as Miconazole and others), the agent used to treat tinea infections. The preferred treatment for erythrasma is a course of oral erythromycin, plus vigorous daily cleansing with soap and water.

Other diseases commonly caused by corynebacteria include trichomycosis axillaris and pitted keratolysis. Patients affected by trichomycosis axillaris present with complaints of a disagreeable underarm odor and a history of hyperhidrosis and poor hygiene. Examination reveals the underarm hair to be coated with black, yellow-white or reddish deposits. Daily cleansing with soap and water generally cures the infection, and regular use of antiperspirants aids in prevention. Topical erythromycin is occasionally required to eliminate the infection.

Patients with pitted keratolysis present with complaints of painful burning of the feet and a history of wearing occlusive footwear in warm, damp environments. Examination reveals small, punctate, pitted lesions on calloused areas of the feet and a disagreeable foot odor. Frequent cleansing of the feet and application of topical erythromycin are generally effective in eliminating the infection. Use of antiperspirants also aids in cure and prevents recurrence.


Impetigo is a common infection in children that may also occur in adults. It is generally caused by either Staphylococcus aureus or streptococci. Patients report skin lesions, often with associated adenopathy, but have minimal systemic signs and symptoms. Impetigo may present in two forms: small vesicles with a honey-colored crust or purulent-appearing bullae. Bullous impetigo is less common than small-vesicle impetigo. S. aureus is the organism that commonly causes bullous impetigo. S. aureus is also the most frequently found organism in small-vesicle impetigo, although group A betahemolytic streptococcus is also a common pathogen in patients over the age of two.[1]

Systemic treatment employs beta-lactamase-resistant antibiotics. Topical mupirocin (Bactroban) is effective in 90 percent of cases and is more effective than oral erythromycin.[1] To date, topical mupirocin has not been compared with other commonly used oral antibiotics, many of which have efficacy superior to that of erythromycin. Application of mupirocin ointment to the nares twice a day for five days may be efficacious in outbreaks of recurrent methicillin-resistant S. aureus skin infection, if the nares are colonized[2] Erythromycin resistance is now common among strains of S. aureus[3] (Figure 1). Rarely, a poststreptococcal illness, such as nephritis, may be a complication when impetigo is caused by certain strains of group A beta-hemolytic streptococci.



Ecthyma occurs in debilitated persons, such as patients with poorly controlled diabetes, and is generally caused by the same organisms that cause impetigo. The patient presents with moderately painful lesions with adherent crusts, generally on the legs; the lesions may subsequently become purulent, poorly healing ulcers. These lesions tend to be deeper seated than those of impetigo.

Improved nutritional status and two to three weeks of treatment with a beta-lactamase-resistant antibiotic are usually required to bring about resolution of the lesions.[4]

Folliculitis and Related Conditions

Patients with folliculitis present with yellowish pustules at the base of hairs, particularly on the scalp, back, legs and arms. Often, the patient lives in a warm, damp climate. Persons with diabetes are particularly susceptible to this infection. Frequent use of soap and water and the use of topical antibiotic agents, such as mupirocin or bacitracin (Neosporin, Polysporin), generally clear the lesions. Occasionally, the addition of a systemic antistaphylococcal agent is required.

Hot-tub folliculitis is a special form of folliculitis caused by Pseudomonas. It occurs when patients bathe in poorly maintained hot tubs. Hot-tub folliculitis is generally a self-limited condition, although the infection can progress to a serious illness in immunocompromised persons. If the lesions do not resolve within five days of discontinuing hot-tub use, therapy with antibiotics such as ciprofloxacin (Cipro) should be considered.[4,5]

Furuncles, or boils, are more aggressive forms of folliculitis. Patients present with a painful, often fluctuant swelling in a non-weight-bearing area, most commonly areas of friction, the nasal area or the external ear. Treatment often requires drainage of the lesion. Antibiotic therapy should be considered if the furuncle is not yet fluctuant, if there is evidence of surrounding cellulitis or lymphadenitis, or if the lesion is on the face. A carbuncle is a collection of furuncles and typically occurs on the back of the neck in middle-aged and older men. The lesions have many interconnecting sinuses and tend to recur despite drainage and antibiotics. Surgical drainage and resection of the lesions is often necessary.

Hidradenitis suppurativa, which initially may be confused with furunculosis, is pathologically related to furuncles.[6] Hidradenitis often affects persons with concurrent acne conglobata, although it may occur in other persons as well. Persons with hidradenitis generally have chronic and recurrent episodes of multiple furuncles in the axillae, mons pubis, scrotum, labial or inguinal areas. Drainage and antibiotics are useful, and hormonal treatment with leuprolide (Lupron) and cyproterone acetate (not available in the United States) has been successful.[7] Patients may also benefit from the use of isotretinoin (Accutane), 0.5 to 2.0 mg per kg daily in two divided doses for 16 to 20 weeks.

While medical treatment offers a conservative approach, studies of the use of leuprolide, cyproterone acetate and isotretinoin in the treatment of hidradenitis are few, and these treatments are not approved by the U.S. Food and Drug Administration. Surgical resection of the affected area is often necessary.[7]


Erysipelas presents acutely as marked redness, pain and swelling in the affected area. Erysipelas may be increasing in frequency, and infection involving the legs has replaced facial infection as the most common site.[8] The lesion has a sharply defined, if somewhat serpiginous, spreading border, and prominent adenopathy is present. The patient may appear systemically ill, with increased temperature and an elevated white blood cell count. The illness is generally believed to be caused by beta-hemolytic streptococci, but recently other organisms have also been implicated.[8,9]

An oral antibiotic, usually penicillin, is sufficient for treatment. Sepsis may occur in persons with diabetes and in immunocompromised persons, and hospital admission should be considered for such patients, as well as for any patient with significant systemic signs and symptoms.


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MICHAEL L. O'DELL, M.D., is associate professor and residency program director in the Department of Family Medicine at the University of Texas Medical Branch at Galveston. Dr. O'Dell graduated from the University of Kansas School of Medicine, Kansas City, Kan., where he completed a residency in family practice.

Address correspondence to Michael L. O'Dell, M.D., Department of Family Medicine, Mail Route 1123, University of Texas Medical Branch-Galveston, Galveston, TX 775551123. Reprints are not available from the author.

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