Spectrum of Disease Due to Rapidly Growing Mycobacteria

One hundred twenty-five cases of disease due to rapidly growing mycobacteria were observed over a four-year period. Cutaneous infections accounted for 74 cases (59%). Of these, 40 followed surgical procedures (especially augmentation mammaplasty or median sternotomy), and 34 were due to accidental penetrating trauma. Among the 24 patients with pulmonary disease, the mean age was ∼60 years, the majority of patients (63%) were women, and most had unilateral noncavitary disease. Other infections included disseminated disease with multiple nodular skin lesions and positive blood cultures, cervical lymphadenitis, keratitis, and endocarditis associated with a prosthetic valve. Infected tissues showed mixed acute and granulomatous inflammation; acid-fast bacilli, when present, occurred in extracellular clumps within microabscesses. Mycobacterium fortuitum and Mycobacterium chelonei were encountered with approximately equal frequency; 80% of isolates of M. chelonei were subspecies abscessus, and 83% of isolates of M. fortuitum were biovariant fortuitum. The outcome in these infections was generally good, although 9% of the patients, including all those with endocarditis, died. Infections due to M. fortuitum and M. chelonei are probably markedly under-diagnosed, and these organiams are capable of causing a wide spectrum of clinical disease.