Overview of rapidly growing mycobacteria

For general information on nontuberculous mycobacterial infections, see Diagnosis of nontuberculous mycobacterial infections and Approach to managing nontuberculous mycobacterial infections.

Mycobacterium abscessus, Mycobacterium chelonae and Mycobacterium fortuitum are rapidly growing mycobacteria that cause skin and soft tissue and respiratory infections, infections of prosthetic material, and infections associated with contact lens use and ocular surgery (especially M. chelonae with laser in situ keratomileusis [LASIK]). Occasionally these organisms cause disseminated infection.

For detail on M. abscessus pulmonary disease, see Mycobacterium abscessus pulmonary disease.

In the majority of patients with M. chelonae or M. fortuitum identified on culture of respiratory samples, the organisms are transient or not contributing to the patient’s symptoms, and treatment is not required. Patients with repeated positive cultures and persistent respiratory symptoms not responding to other treatments are more likely to need treatment.

Treatment is complex; it depends on the site of infection, and is guided by the results of susceptibility testing. Adjunctive surgery may be required.

If treatment is required for M. fortuitum, use a combination of two oral drugs with demonstrated in vitro susceptibility—options usually include doxycycline, ciprofloxacin or trimethoprim+sulfamethoxazole. Macrolides are not first-line treatment because all isolates have inducible erythromycin methylase (erm) genes, which can produce macrolide resistance despite initial in vitro susceptibility.

For respiratory disease caused by M. chelonae or M. fortuitum, continue treatment until the patient’s sputum is culture-negative for at least 12 months.

For severe skin and soft tissue infection caused by rapidly growing mycobacteria, the minimum duration of treatment is 4 months. For bone infection, 6 months of treatment is recommended. A longer duration of treatment is usually required in immunocompromised patients.