Chemotherapy of Tuberculosis: A Bacteriologist’s Viewpoint’

Abstract

In pulmonary tuberculosis chemotherapy with isoniazid, and probably streptomycin, completely prevents further growth of sensitive tubercle bacilli early in treatment. Viable sensitive bacilli obtained from the sputum during treatment appear to be the remnants of the original population which have persisted in a dormant state. Neither p-aminosalicylic acid nor thiacetazone inhibits growth so completely, and the occasional failure of a double-drug regimen of isoniazid plus P.A.S. or isoniazid plus thiacetazone is due to the growth of isoniazid-resistant mutants in the presence of these drugs. Triple-drug therapy (or possibly isoniazid plus streptomycin) is highly successful in preventing growth of sensitive bacilli and resistant mutants ; the occasional resistant strain isolated during treatment is not due to growth of mutants and does not carry a poor prognosis. Factors such as initially severe disease and the concomitant administration of corticosteroids, which result in a poor response when inefficient chemotherapy is given, are of little prognostic importance with potent drug treatment ; it is the drugs that kill the bacilli and not the patient’s immune response. In consequence, measures of treatment other than efficient chemotherapy are largely unnecessary, and the control of treatment should be based on smear and culture examinations of sputum. © 1965, British Medical Journal Publishing Group. All rights reserved.