Methicillin-resistant Staphylococcus aureus (MRSA), an established nosocomial pathogen, has recently emerged as an important cause of skin and soft tissue infections among patients who have not been hospitalized. Though infections are not specifically associated with HIV-related immunosuppression, they co-exist in many risk groups seen by HIV providers and are becoming increasingly common in HIV practice. These community-associated MRSA (CA-MRSA) infections have frequently been identified through outbreak investigations affecting athletes, inmates, military recruits, and men who have sex with Injection drug use, homelessness, and the prior use of antimicrobial agents within the previous 6 months have also been associated with CA-MRSA infections.

CA-MRSA strains are remarkably similar worldwide, differing from hospital-acquired MRSA strains in 1) their susceptibility to a variety of oral antibiotics (excluding lactams); 2) the presence of type IV staphylococcal chromosomal cassette mec (SCCmec); and 3) the presence of genes that encode certain toxins, such as Pantone-Valentine leukocidin. The origin of CA-MRSA strains is uncertain, but molecular typing studies of MRSA isolates in a large San Francisco health care network identified strains that had evolved both from existing hospital strains and de novo in the community.

Patients with CA-MRSA infections may present with skin and soft tissue infections such as furuncles, deep-seated folliculitis, impetigo, abscesses, or ecthyma. During CA-MRSA outbreaks, patients have frequently sought medical attention for a "spider bite," or a "sore." CA-MRSA can also cause serious systemic infections including pneumonia, osteomyelitis, septic arthritis, endocarditis, and sepsis. No differences in overall disease severity have been established between CA-MRSA and nosocomial MRSA infections. Persons with HIV infection may be at greater risk for CA-MRSA infections based on associated risk behaviors or the presence of conditions that may increase the risk of acquiring Staphylococcus aureus infections such as severe skin disease, diabetes, chronic renal failure on hemodialysis, recent surgery, or the need for indwelling catheters.

The emergence of CA-MRSA infections further complicates the management of outpatients presenting with skin and soft tissue infections. On initial assessment all skin infections should be carefully examined for cellulitis, fluctuance, crepitus, and sinus drainage. Incision and drainage is the treatment of choice, and antibiotics are often unnecessary. Whenever feasible, incision and drainage should be pursued as the initial treatment. Furuncles and small abscesses can be drained with local anesthesia; whereas surgical consultation is often indicated for larger abscesses and infections of the face or hands.
fluctuance, crepitus, and sinus drainage. Incision and drainage is the treatment of choice, and antibiotics are often unnecessary. Whenever feasible, incision and drainage should be pursued as the initial treatment. Furuncles and small abscesses can be drained with local anesthesia; whereas surgical consultation is often indicated for larger abscesses and infections of the face or hands.
Any wound drainage should be sent for routine bacterial cultures and antibiotic sensitivities, since the etiology of these infections can not be differentiated clinically and treatment can be targeted by identifying the offending pathogen. In some cases, incision and drainage alone will adequately resolve minor infections without antibiotic therapy.

Empiric antibiotic therapy is indicated for patients with large or multiple furuncles, soft tissue abscesses, cellulitis, deep-seated folliculitis, impetigo, ecthyma, systemic disease or symptoms, or who are otherwise at high risk for serious complications, such as patients with prosthetic valves or previously diagnosed endocarditis. Treatment should be adjusted based on culture data and antibiotic susceptibilities, however the optimal choice for treating any specific CA-MRSA infection is unknown, since no controlled trials have assessed whether in vitro antibiotic susceptibilities correlate with clinical response. A specific treatment regimen should therefore be made on a case by case basis after weighing: antibiotic susceptibilities, patient-specific factors, and the risks and benefits of various therapeutic options. Antibiotic selection for CA-MRSA infections does not differ for patients with or without HIV infection.