The cornerstone of contemporary treatment of tuberculosis is chemotherapy. The ideal objective of chemotherapy of tuberculosis is elimination of all disease-causing parasites from the patient. However, there is much evidence to show that this ideal objective is seldom attained. Therefore, practical objectives have been formulated.
The short-term practical objective of the chemotherapy of tuberculosis is control of the disease process of the individual patient. That this objective has been achieved is demonstrated by conversion of the sputum to bacteriological negativity for Mycobacterium tuberculosis. The long-term practical objective of the chemotherapy of tuberculosis is the prevention of bacteriologie relapse.
Failure of chemotherapy may be failure to control the disease process, or it may be failure to prevent relapse. The failure of chemotherapy is manifested by sputum (or other pathological material) which is continuously bacteriologically positive for Mycobacterium tuberculosis or has become bacteriologically positive anew after a period of bacteriologically negative