given. Therapy for latent infection is aimed at eradicating thepresumably small inoculum of organisms sequestered withinmacrophages and suppressed by normal T cell activity. Toprevent reactivation of these latent bacilli, therapy with a single agent (usually isoniazid for 9 months) is suggested. Children with primary pulmonary tuberculosis and patients withextrapulmonary tuberculosis have medium-sized populationsin which significant numbers of drug-resistant organisms mayor may not be present. In general these patients are treated withat least two drugs (Table 124-3) for a prolonged course, typically6 to 9, depending on the type of disease. Isoniazid and rifampinare bactericidal for M. tuberculosis and are effective against allpopulations of mycobacteria. Along with pyrazinamide, theyform the backbone of the antimicrobial treatment of tuberculosis. Other drugs are used in special circumstances, such astuberculous meningitis and antibiotic-resistant tuberculosis.
A 9-month regimen of isoniazid and rifampin cures greater than 98% of cases of drug-susceptible pulmonary tuberculosis. After daily administration for the first 1 to 2 months, both drugs can be given daily or twice weekly for the remaining 7 to 8 months, with equivalent results and low rates of adverse reactions. The addition of pyrazinamide for the first 2 months of the regimen reduces the total duration of treatment to 6 months and has similar efficacy. Noncompliance, or nonadherence, is a major problem in tuberculosis control because of the long-term nature of treatment and the sometimes difficult social circumstances of the patients. As treatment regimens become shorter, adherence assumes an even greater importance. Improvement in compliance occurs with directly observed therapy, which means that the health care worker is physically present when the medications are administered, and is the standard of care in most settings.
The prognosis of tuberculosis in infants, children, and adolescents is excellent with early recognition and effective chemotherapy. In most children with pulmonary tuberculosis, the disease completely resolves, and ultimately radiographic findings are normal. The prognosis for children with bone and joint tuberculosis and tuberculous meningitis depends directly on the stage of disease at the time antituberculosis medications are started. Tuberculosis of the spine may result in angulation or gibbus formation that requires surgical correction after the infection is cured. Most childhood tuberculous meningitis occurs in developing countries, where the prognosis is poor.
Tuberculosis control programs involve case finding and treatment, which interrupts secondary transmission of infection from close contacts. Infected close contacts are identified by positive TST reactions and can be started on appropriate treatment to prevent transmission.
Prevention of transmission in health care settings involves appropriate physical ventilation of the air around the source case. Offices, clinics, and hospital rooms used by adults with possible tuberculosis should have adequate ventilation, with air exhausted to the outside (negative-pressure ventilation).Health care providers should have annual TSTs.
The only available vaccine against tuberculosis is the bacille Calmette-Guérin vaccine. The original vaccine organism was a strain of Mycobacterium bovis attenuated by subculture every 3 weeks for 13 years. The preferred route of administration is intradermal injection with a syringe and needle because this is the only method that permits accurate measurement of an individual dose. The official recommendation of the World Health Organization is a single dose administered during infancy. This vaccine is not routinely used in the United States. Some studies show bacille Calmette-Guérin to provide 80% to 90% protection from tuberculosis, and other studies show no protective efficacy at all. Many infants who receive bacille Calmette-Guérin vaccine never have a positive TST reaction. When a reaction does occur, the induration size is usually less than 10 mm, and the reaction wanes after several years.