Tuberculosis: An Update for Clinicians

Tuberculosis is the most common cause of death due to a single pathogen world wide, and the number of tuberculosis cases in the United States has increased significantly since 1985. Drug-resistant tuberculosis is also increasing, and multidrug-resistant tuberculosis (resistant to isoniazid and rifampin) has fueled deadly epidemics in New York and Florida. The clinical manifestations of tuberculosis in patients with human immunodeficiency virus (HIV) infection are distinctive; chest radiographic findings include primary tuberculosis and an extremely high frequency of extrapulmonary tuberculosis. Promising new diagnostic tests for tuberculosis are based on amplification of mycobacterial DNA by polymerase chain reaction, but they have not yet been adapted to the clinical laboratory. Most tuberculosis patients in the United States should receive initial treatment with isoniazid, rifampin, pyrazinamide, and ethambutol. For drug-susceptible tuberculosis, these drugs are continued for 2 months, followed by isoniazid and rifampin for 4 months, which yields a cure rate of greater than 95%. For isoniazid-resistant organisms, rifampin, pyrazinamide, and ethambutol, with or without isoniazid, can be given for 6 months. For HIV-infected patients with drug-susceptible or isoniazid-resistant tuberculosis, we recommend continuation of therapy for a minimum of 9 months. Most forms of extrapulmonary tuberculosis due to drug-susceptible organisms are treated for 6 months, except for meningeal, miliary, and skeletal tuberculosis, for which a minimum of 12 months of therapy is recommended. To reduce nosocomial transmission of tuberculosis, health cafe facilities should institute administrative controls to reduce exposure to infectious patients, engineering controls to reduce the concentration of infectious droplet nuclei, and personal respiratory protection of health care workers with appropriate masks. Administrative controls are probably the most important part of a tuberculosis infection control program. Health care workers who were recently infected with Mycobacterium tuberculosis can be identified by serial skin testing, and those who convert their skin tests from negative to positive should receive chemoprophylaxis with isoniazid to prevent development of tuberculosis.