The early bactericidal activity of drugs in patients with pulmonary tuberculosis.

Abstract

Counts of colony-forming units of Mycobacterium tuberculosis in sputum were done on selective medium during the first 2 wk of treatment of 124 patients with pulmonary tuberculosis. The 27 chemotherapy regimens studied included daily administration of thiacetazone, p-aminosalicylic acid, pyrazinamide, rifampin, streptomycin, ethambutol, and isoniazid alone and certain 2-drug, 3-drug, and 4-drug combinations. Thiacetazone and p-aminosalicylic acid appeared to be only bacteriostatic. The mean fall in counts and the differences between regimens containing the remaining bactericidal drugs were greater during the first 2 days of treatment than during the remaining 12 days. The early (0-to-2-day) falls were much larger with isoniazid than with other drugs. Rifampin was less bactericidal, and may have reduced the bactericidal activity of the 3-drug and 4-drug combinations, including isoniazid. Although streptomycin and pyrazinamide were only slightly bactericidal alone or in a 2-drug combination, the 3-drug regim...