Bacterial skin problems such as folliculitis, infection of the hair follicles, are commonly caused by S. aureus. Folliculitis is characterised by a reddened skin area, pimples or pustules around the hair follicles. S. aureus can also cause bullous impetigo, fluid filled blisters, often in the groin or armpit. These conditions normally respond to treatment with antibiotics such as penicillin or cephalosporins.

The drug-resistant methicillin-resistante S. aureus (MRSA) can also attack otherwise healthy skin and affects unusual parts of the body, including the legs, buttocks, penis and scrotum. It can also infect the blood, lungs and other sites. This form of bacterium can be difficult to treat. Although often associated with hospital treatment, community-acquired MRSA is a rising problem, through contact with the bacterium in sports facilities and other venues.

Recent evidence has suggested that its prevalence may be on the increase, particularly among HIV-positive gay men, with one study showing an association with high-risk sex and drug-using behaviour^[1]. Another study found a particular association with recent treatment for syphilis, suggesting to some investigators that MRSA may be acquired in bathhouses or saunas^[2]. However, studies disagree on whether CD4 cell counts and antiretroviral therapy affect the likelihood of infection with MRSA^[3], ^[4], ^[5].

Itchy folliculitis occurring in people with low CD4 cell counts is often not due to bacterial infection, but immune dysregulation. Lesions should be biopsied to determine whether or not they are bacterial or not.

Pyomyositis is a condition which occasionally affects people with advanced HIV disease. It causes inflammation and pus-filled abscesses in the muscles. This can result in fever and painful swelling of the soft tissue in the legs, and may need surgical drainage and prolonged antibiotic treatment.

Bacillary angiomatosis is a relatively recently described condition that is sometimes called cat scratch disease. On the skin it causes painless lesions that resemble Kaposi's sarcoma. It can also affect the internal organs, causing fever, abdominal pain and liver failure. Bacteria belonging to the Bartonella group are thought to be the cause^[6][7][8]. The mode of infection is not clear, but there is some evidence to suggest that cats may carry the bacteria. The skin lesions usually clear up promptly after treatment with the antibiotic erythromycin (Erymax / Erythrocin / Erythroped / Erythroped A / Tiloryth), and may also improve internally. Alternative treatments are azithromycin (Zithromax) or itraconazole (Sporanox).