Susceptible Organisms
When infection proves to be caused by a fully susceptible strain of TB, the initial phase of treatment should include isoniazid, rifampin and pyrazinamide. If pulmonary cavitation is not present on the initial chest X-ray and the patient has a negative AFB smear at 2 months, isoniazid plus rifampin or rifapentine, a long-acting rifamycin, can be given for the next 4 months (continuation phase) to complete a total of 6 months. For patients with a positive AFB culture at 2 months and cavitary lung disease, continuation therapy with isoniazid and rifampin is extended to 7 months (for a total duration of therapy of 9 months). Rifampin, not rifapentine, should be used for continuation therapy if there is cavitary lung disease, a positive AFB smear at 2 months, coinfection with HIV, extrapulmonary disease, or infection in children.