Staphylococcus aureus, Skin & Soft Tissue Infections

Key Features

• Localized erythema with induration and purulent drainage

• Abscess formation

• Gram stain of pus shows gram-positive cocci in clusters

Clinical Findings

• May begin around one or more hair follicles, causing folliculitis

• May become localized to form boils (or furuncles)

• May spread to adjacent skin and deeper subcutaneous tissue (ie, a carbuncle)

• Deep abscesses involving muscle or fascia may occur, often in association with a deep wound or other inoculation or injection

• Necrotizing fasciitis has been reported with community strains of methicillin-resistant S aureus (MRSA)

Diagnosis

• Cultures of the wound or abscess material almost always yields the organism

• In patients with systemic signs of infection, blood cultures should be obtained because of potential bacteremia, endocarditis, osteomyelitis, or metastatic seeding of other sites

• Patients who are bacteremic should have blood cultures taken early during therapy to exclude persistent bacteremia, an indicator of severe or complicated infection

Treatment

• Proper drainage of abscess fluid or other focal infections is the mainstay of therapy

• Incision and drainage alone is highly effective for the treatment of most uncomplicated cutaneous abscesses

• A small benefit can be obtained from the addition of antimicrobials following incision and drainage.

• In areas where methicillin-resistance among community S aureus isolates is high, recommended oral antimicrobials agents include

  • Clindamycin, 300 mg three times daily

  • Trimethoprim-sulfamethoxazole, given in two divided doses based on 5–10 mg/kg/day of the trimethoprim component

  • Doxycycline or minocycline, 100 mg twice daily

• When the risk of methicillin-resistance is low or methicillin-susceptibility has been confirmed by testing of the isolate, consider

  • Dicloxacillin or cephalexin, 500 mg four times a day

• For complicated infections with extensive cutaneous or deep tissue involvement or fever, initial parenteral therapy is often indicated

• When methicillin resistance rates are high (above 10%) empiric therapy with vancomycin, 1 g intravenously every 12 hours, is a drug of choice

• For infections caused by methicillin-susceptible isolates

  • Cefazolin 1 g intravenously or intramuscularly or

  • A penicillinase-resistant penicillin such as nafcillin or oxacillin in a dosage of 1.5 g every 6 hours intravenously

• For treatment of skin and skin-structure infections

  • Linezolid, 600 mg orally or intravenously twice a day for 10–14 days

    • Effective for MRSA

    • However, considerable cost makes it an unattractive choice for most routine outpatient infections

  • Other alternatives

    • Tedizolid, 200 mg orally once daily for 6 days

    • Daptomycin, 4 mg/kg once daily intravenously for 7–14 days

    • Tigecycline, 100 mg intravenously once, followed by 50 mg intravenously twice a day for 7–14 days

    • Ceftaroline, 600 mg intravenously twice a day for 7–14 days

    • Dalbavancin, a single intravenous dose of 1500 mg

    • Oritavancin, 1200 mg as a single intravenous dose

    • Telavancin, 10 mg/kg intravenously once daily for 7–14 days

    • Delafloxacin, 450 mg orally or 300 intravenously twice daily for 5–14 days

• Duration of therapy

  • Total duration ...