The course of pulmonary tuberculosis in patients excreting organisms which have acquired resistance. Response to continued treatment for a second year with isoniazid alone or with isoniazid plus PAS.

This study from the Tuberculosis Chemotherapy Centre, Madras, summarizes the progress during the second year of the patients in a concurrent comparison of four domiciliary chemotherapeutic regimens (isoniazid plus PAS and three regimens of isoniazid alone) who had bacteriologically active or bacteriologically relapsed pulmonary tuberculosis, with isoniazid-resistant organisms, at the end of the first year of treatment.Of the 57 patients who continued on the same chemotherapy during the second year, nine had attained bacteriological quiescence by the end of that year, 15 still had bacteriologically active disease and 33 had during the year had a serious radiographic deterioration necessitating a change of treatment. An association was observed between the response to treatment in the second year and both the extent of cavitation and the degree of culture-positivity at the end of the first year, but no association was found between the response to treatment in the second year and the level of isoniazid-resistance, the catalase activity, the susceptibility to hydrogen peroxide or the virulence in the guinea-pig of cultures isolated in the last months of the first year.It is concluded that persisting bacteriological positivity at the end of one year's treatment with isoniazid, either alone or in combination with PAS, is likely to lead to serious radiographic deterioration, irrespective of the level of isoniazid-resistance or of the catalase activity of the cultures of tubercle bacilli, and that, consequently, treatment of patients with bacteriologically active pulmonary tuberculosis must aim at rendering the sputum culture-negative in all instances.