Persistent Cutaneous Infection Due to Mycobacterium Immunogenum, a Relatively Novel Species

Abstract

A 30-year-old female presented to the dermatology clinic for an evaluation of a tender lesion on her right leg that was increasing in size. The lesion was first noted two months ago during a vacation in Hawaii. The patient denied any trauma to the area, but stated she swam in the ocean and swimming pools while on vacation. No pruritus, drainage, or bleeding was noted. On physical exam, the patient had a violaceous, indurated nodule on the right anterior distal leg with poorly defined borders, overlying fine white scale, and surrounding erythema (Figure 1). The lesion was initally diagnosed as a staphylococcal abscess, but did not improve after taking amoxicillin/clavulanic acid (875 mg /125mg twice daily for 3 days) and applying warm compresses. Amoxicillin/clavulanic acid was discontinued, doxycycline (100 mg twice daily for 10 days) was initiated, and the patient was instructed to take twice-weekly dilute bleach baths.Twenty-four hours later, the patient returned after developing purulent drainage. On ABSTRACTMycobacterium immunogenum is a species of nontuberculous mycobacteria (NTM) that has been recently identified as the cause of cutaneous infections.1-3 Historically, the majority of NTM infections were attributed to contamination of municipal water systems due to inadequate equipment sterilization. Many of these organisms have been found to grow in distilled water and display resistance to chlorine, formaldehyde, mercury, and standard disinfectants. 4 In the environment, M. immunogenum has been isolated in swimming pools and adjacent showers.5 A limited number of cutaneous infections with Mycobacterium immunogenum have been reported, and an even smaller number of cases have been reported in immunocompetent individuals. We report a case of a persistent cutaneous infection with M. immunogenum in a previously healthy patient successfully treated with clarithromycin 250 mg twice daily for eight weeks. After treatment, the patient remained free of infection and only a minimal scar remained. CASE REPORT