Mycobacterium fortuitum Infection

A 35-year-old veterinary technician who lived in south central Texas presented with a raised, warm, tender 2- to 3-cm papule on her lower leg of more than 2 weeks' duration. Topical mupirocin and oral trimethoprim/ sulfamethoxazole were prescribed, but the papule continued to enlarge and became increasingly erythematous and painful.

The patient suspected a spider bite, but she could not recall being bitten. She had not been scratched or bitten by an animal at work. She denied fever, chills, myalgia, and fatigue.

The mildly fluctuant lesion was incised and drained, and a specimen was obtained for wound culture. Antibiotic therapy was continued, and the wound was repacked daily. After a week, the wound remained unchanged.

Scott Carrizales, MD, of San Antonio, Tex, reports that culture results revealed rare acid-fast bacilli. Treatment with oral ciprofloxacin was started and then switched to oral doxycycline after Mycobacterium fortuitum was identified. Six weeks later, the lesion had healed.

M fortuitum is one of more than 50 pathogenic nontuberculous mycobacteria (NTM) that can cause localized skin infection in immunocompetent persons. M fortuitum and the Mycobacterium chelonae/abscessus group make up the broader class of rapidly growing NTM, classified as Runyon group IV mycobacteria. Of all the NTM, the rapidly growing Mycobacterium species and Mycobacterium marinum--which can be found in aquariums--are the most common causes of skin lesions.¹ NTM also cause isolated cutaneous lesions in dogs and cats; however, transmission is atypical and is not thought to have caused the infection in this patient.

Mycobacterium infections usually result from local inoculation from lacerations or other wounds, but they have also been associated with contaminated surgical instruments and nail salons.²M fortuitum is endemic to the soil and domestic water systems in the southeastern United States from Georgia to Texas.

Cutaneous infections consist of localized, erythematous lesions that may develop into furuncles and carbuncles. Diagnosis is made by wound culture or tissue biopsy. Disseminated NTM infection typically occurs only in immunocompromised patients.

Prolonged antibiotic therapy is recommended for localized M fortuitum infections. The choice of antibiotic is based on susceptibilities, when available. Options include intravenous amikacin or imipenem/ cilastatin; oral cefoxitin, ciprofloxacin, clarithromycin, or doxycycline; and the sulfonamides.³

References:

REFERENCES:

1.

Brown BA, Wallace RJ. Infections due to nontuberculous mycobacteria. In: Mandell GL, Bennett JE, Dolin R, eds.

Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases.

5th ed. Philadelphia: Churchill Livingstone; 2000:2630-2635.

2.

Elston DM. New and emerging infectious diseases.

J Am Acad Dermatol.

2005;52:1062-1068.

3.

Garman ME, Orengo I. Unusual infectious complications of dermatologic procedures.

Dermatol Clin.

2003;21:321-335.