Dermatologic Staphylococcal Infections

July 2006

Chapter Contents

Background

Subjective

Objective

Assessment

Plan

Patient Education

References

Background

Staphylococcus aureus is the most common cause of community-acquired (CA) or hospital-acquired (HA) bacterial skin and soft-tissue infections (SSTIs) among patients with HIV infection. Staphylococcal infection may present as cellulitis, folliculitis, furuncles, abscesses, ecthyma, bullous impetigo, or plaques resembling hidradenitis suppurativa. Staphylococcal SSTIs can occur in isolation or as a complication of other skin pathology. HIV-positive patients are at risk of superinfection, bacteremia, and metastatic infection from SSTIs that might be considered trivial in other patients.

Most CA staphylococcal infections involve methicillin-susceptible S aureus (MSSA). However, a strain of CA methicillin-resistant S aureus (MRSA) is increasingly common; MRSA is now found in up to 50% of CA SSTIs in many localities. This strain carries an SSTI virulence gene (the Panton-Valentine leucocidin gene), is more aggressive in causing SSTIs, and appears more likely to result in serious pneumonia than was previous CA S aureus . Resistance is conferred by the mec IV gene (different from mec III of HA MRSA). CA MRSA is commonly sensitive to tetracyclines, rifampin, trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, and clindamycin.

The treatment of SSTIs is determined by the extent, depth, and speed of progression of the infection. Hospital admission for intravenous antibiotic therapy is indicated when systemic toxicity accompanies a staphylococcal skin infection, the infection is rapidly advancing, or there is concern about compartment syndrome, necrotizing fasciitis, or other complications.

S: Subjective

The patient complains of inflammation (erythema and tenderness) of the skin and subcutaneous tissue, itchy rash (folliculitis), furuncles, pustules, or abscesses.

Inquire about the following:

• Risk factors, including other recent skin infections, trauma, hospitalization, close skin contact with other people (especially those with skin infections), injection drug use, diabetes mellitus, chronic venous insufficiency
• Constitutional symptoms, such as fever
• Localizing pain
• Symptoms distant from the index lesion, which may suggest systemic spread

Review medications, supplements, and herbal preparations.

O: Objective

Physical Examination

Note: SSTIs may be highly contagious. During examination of any skin lesions, the health care worker should wear gloves and wash hands thoroughly after glove removal.

Check vital signs. Perform a focused physical examination of the skin, lymph nodes, and other areas as indicated (eg, the heart for signs of endocarditis, the mucous membranes for lesions, or the joints for signs of septic arthritis).

Cellulitis

Findings include swelling, tenderness, erythema, and warmth of localized tissue, most commonly on the face and extremities. Cellulitis may be associated with other types of lesions.

Furuncles/abscesses

Palpation of the affected area reveals a firm nodule or a fluid collection in the subcutaneous tissue, often surrounded by cellulitis. Most abscesses or furuncles with more than a few microliters of pus should be drained.

Folliculitis

Follicular pustules are pruritic, often very painful lesions that may be present on the face, trunk, axillae, or groin. A tiny central pustule may be visible when the skin is stretched, although sometimes the lesions are almost urticarial. These may extend below the skin surface, forming abscesses or, in rare cases, large, violaceous hidradenitis-like plaques with pustules. Note that excoriations may obscure primary lesions.

Ecthyma

This appears as a superficially ulcerated "punched out" or eroded lesion with an extremely adherent crust. A purulent layer of material is usually found under the crust.

Bullous impetigo

Superficial blisters or erosions, often with yellow crusts, appear on the face, groin, or axillae.

A: Assessment

A partial differential diagnosis of cellulitis, abscess, eruptions, or ulcerations includes the following:

• Streptococcal or other bacterial SSTI
• Candida albicans or other fungal infection (particularly in the groin and perineal area and under pendulous breasts, or as a cause of folliculitis)
• Eosinophilic folliculitis
• Syphilis
• Herpes simplex, herpes zoster
• Cutaneous hypersensitivity reactions to drug therapy
• Deep vein thrombosis in the calf, causing swelling with apparent cellulitis
• Pyogenic granuloma
• Angiosarcoma
• Kaposi sarcoma, particularly if femoral or inguinal lymph node enlargement is present
• Bacillary angiomatosis
• Gout

P: Plan

Diagnostic Evaluation

Often, SSTIs can be diagnosed and treated on the basis of the history and physical examination, and diagnostic testing is not required.

For exudative or pustular lesions, obtain exudate for Gram stain, culture, and sensitivity, to identify the organism and to choose the optimal antibiotic therapy. Note that CA MRSA is common among HIV-infected patients in most urban and many rural areas.

If systemic illness is suspected, check complete blood count with differential, blood cultures, and a metabolic panel.

Order tests to rule out other causes of skin infection, as indicated (eg, syphilis, herpes). Consider biopsy if the diagnosis is unclear after initial workup or if the lesion does not respond to empiric treatment.

Treatment

If the patient has extensive, spreading cellulitis or systemic illness, or is suspected to have deep abscess, necrotizing infection, compartment syndrome, or other deep soft-tissue infection, hospitalize immediately for intravenous antibiotic therapy (consult an infectious disease specialist for antimicrobial therapy) and obtain urgent surgical consultation. Mild and moderate SSTIs can usually be treated on an outpatient basis.

Abscesses and fluctuant lesions should be incised and drained, if possible. Antibiotic therapy may not be necessary if the abscess is drained adequately.

For suspected S aureus infections, initiate empiric antibiotic treatment, if indicated; consider the local prevalence of MRSA when selecting antibiotics (see " Treatment note " below).

Impetigo

Treat impetigo for 7-14 days.

• Dicloxacillin 250 mg orally 4 times per day
• Cephalexin 250 mg orally 4 times per day
• Erythromycin 250 mg orally 4 times per day
• Clindamycin 300-450 mg orally 4 times per day
• Doxycycline 100 mg orally twice daily

Known or suspected MSSA SSTI

Treat known or suspected MSSA SSTIs for 7-14 days.

• Dicloxacillin 500 mg orally 4 times per day
• Cephalexin 500 mg orally 4 times per day
• Clindamycin 300-450 mg orally 4 times per day; if the patient has been taking azithromycin for Mycobacterium avium complex prophylaxis, staphylococcal infections may be resistant to clindamycin
• Doxycycline 100 mg twice daily orally
• TMP-SMX 2 double-strength tablets orally twice daily

Known or suspected MRSA SSTI

Treat according to the patient's culture and sensitivity results, or according to local trends in MRSA susceptibility (see " Treatment note " below). The following are often effective:

• Clindamycin 300-450 mg orally 4 times per day
• Doxycycline 100 mg orally twice daily
• TMP-SMX 2 double-strength tablets orally twice daily

For severe infections, use intravenous antibiotics selected according to S aureus susceptibility. For MRSA, consider vancomycin, clindamycin, linezolid, or daptomycin, if available.

Recurrent lesions may indicate MRSA carriage in the nose or elsewhere. Nasal carriage can be treated with topical mupirocin ointment to the anterior nares 3 times daily for 7 days. If nasal mupirocin fails and MRSA SSTI recurs frequently, the addition of a quinolone or TMP-SMX (2 double-strength tablets twice daily) plus rifampin (600 mg twice daily) to mupirocin nasal ointment for 14-21 days may be effective. With all treatments, staphylococcal eradication may be temporary.

Treatment note

To guide empiric antimicrobial therapy, monitor the percentage of staphylococcal isolates that are MRSA in the particular clinical setting, as well as local MRSA antibiotic sensitivities. (The laboratory must perform the "D-test" to rule out erythromycin induction of clindamycin resistance.)

Patient Education

• Patients should be informed that impetigo and some other staphylococcal infections are highly contagious. Patients should avoid hand contact with lesions, and should not allow other people to touch the affected areas.
• Antibiotics should be taken exactly as prescribed.
• Patients should call or return to the clinic if symptoms do not improve in 3-5 days or if symptoms worsen.
• Instruct patients to wash the affected area with antibacterial soap (such as Hibiclens, Betadine, or benzoyl peroxide wash). If living quarters are shared, patients should clean contaminated surfaces to protect others from MRSA colonization or infection.
• Instruct patients to use warm soaks in aluminum acetate astringent solution (Domeboro solution) if needed for discomfort or irritation.

References

• Berger TG. Dermatologic Care of the AIDS Patient . In: Sande MA, Volberding PA, eds. The Medical Management of AIDS. 6th ed . Philadelphia: WB Saunders; 1999:185-194.
• Ruhe JJ, Monson T, Bradsher RW, et al. Use of long-acting tetracyclines for MRSA infections: case series and review of the literature . Clin Infect Dis. 2005 May 15;40(10):1429-34.
• Sande MA, Eliopoulos GM, Moellering RC, et al. The Sanford Guide to HIV/AIDS Therapy, 14th ed . Hyde Park, VT: Antimicrobial Therapy, Inc.; 2005.
• Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections . Clin Infect Dis. 2005 Nov 15;41(10):1373-406.