Treatment of latent Mycobacterium tuberculosis infection is an essential component of tuberculosis control and elimination. The current standard regimen of isoniazid for 9 months is efficacious but is limited by toxicity and low rates of treatment completion.

ORGANISMS of the Mycobacterium avium complex have long been recognized as an uncommon cause of pneumonia in persons with chronic lung disease.^{1 2 3 4} Organisms of this complex, which comprises two closely related species, M. avium and M. intracellulare, appear to have little virulence in the normal host. Before the acquired immunodeficiency syndrome (AIDS) epidemic, disseminated infection with M. avium complex was extremely rare; by 1980, only 24 cases had been reported in the medical literature.⁵ Beginning in 1982, however, when the infection was recognized in patients with AIDS, the number of cases increased dramatically.At first, the minimal inflammatory response . . .

Latent tuberculosis infection (LTBI) is characterised by the presence of immune responses to previously acquiredMycobacterium tuberculosisinfection without clinical evidence of active tuberculosis (TB). Here we report evidence-based guidelines from the World Health Organization for a public health approach to the management of LTBI in high risk individuals in countries with high or middle upper income and TB incidence of <100 per 100 000 per year. The guidelines strongly recommend systematic testing and treatment of LTBI in people living with HIV, adult and child contacts of pulmonary TB cases, patients initiating anti-tumour necrosis factor treatment, patients receiving dialysis, patients preparing for organ or haematological transplantation, and patients with silicosis. In prisoners, healthcare workers, immigrants from high TB burden countries, homeless persons and illicit drug users, systematic testing and treatment of LTBI is conditionally recommended, according to TB epidemiology and resource availability. Either commercial interferon-gamma release assays or Mantoux tuberculin skin testing could be used to test for LTBI. Chest radiography should be performed before LTBI treatment to rule out active TB disease. Recommended treatment regimens for LTBI include: 6 or 9 month isoniazid; 12 week rifapentine plus isoniazid; 3–4 month isoniazid plus rifampicin; or 3–4 month rifampicin alone.

The prevention of active tuberculosis through the treatment of latent tuberculosis infection is a major element of the national strategy for eliminating tuberculosis in the United States. Targeted treatment for persons who are at the highest risk for reactivation tuberculosis will be needed to achieve this goal. A more precise assessment of the lifetime risk of reactivation tuberculosis, usually estimated at 5 to 10 percent, could help to identify patients who are at the highest risk and motivate them to complete treatment. Currently, the rate of completion of treatment is low.

The frequency of infection with multidrug-resistant Mycobacterium tuberculosis is increasing. We reviewed the clinical courses of 171 patients with pulmonary disease due to M. tuberculosis resistant to rifampin and isoniazid who were referred to our hospital between 1973 and 1983. The patients' records were analyzed retrospectively. Their regimens were selected individually and preferably included three medications that they had not been given previously and to which the strain was fully susceptible.