Cutaneous Mycobacterium Infection

This rash, which covered a 68-year-old woman's body, was noted to have worsened during the past 2 months. A cephalosporin antibiotic had failed to clear the condition. The patient, a nursing home resident, suffered from emphysema, asthma, and heart disease. She had been receiving oxygen therapy and prednisone for 1 year.

Numerous abscesses were present on her right arm, face, and legs. The initial culture and sensitivity studies of material from a lesion yielded Staphylococcus epidermidis and diphtheroids. A trial of amoxicillin/clavulanate potassium was instituted but proved ineffective.

A specimen from a 4-mm punch biopsy of the right arm found a granulomatous and suppurative dermatitis. Acid-fast stains showed cutaneous mycobacterial infection. Additional cultures specific for mycobacteria yielded Mycobacterium chelonai subsp abscessus, a rapid-growing, acid-fast bacillus that is a strict aerobe. In vitro susceptibility studies performed by the CDC determined minimal inhibitory concentrations of 128 µg/mL for amoxicillin/clavulanate (resistant) and 0.25 µg/mL for clarithromycin (susceptible). Clarithromycin, 500 mg bid for 6 months, was given to the patient, whose abscesses began to clear shortly after this regimen was started.

M chelonai is found in soil, house dust, and domestic water supplies and may be resistant to chlorination. Infection occurs where the organism enters areas of broken skin, such as surgical excision or injection sites.

Cutaneous mycobacterial infections are rare but are particularly important for the immunocompromised patient. Therefore, include this condition in the differential when a granulomatous pathology is discovered by a punch biopsy, and consider performing acid-fast staining.