Which of the following anti TB drugs acts on extracellular organisms and is bactericidal drug?: (A) Isoniazid, (B) Streptomycin, (C) Rifampicin, (D) Ethambutol
Answer is B. Streptomycin is the only anti-TB drug which acts on extracellular organisms and is bactericidal. All first line antitubercular drugs are bactericidal except ethambutol which is bacteriostatic. Impoant points about first line ATT: Drug Action Hepatotoxic Bacteria Inhibited Isoniazid CIDAL Yes Both Rifampicin CIDAL Yes Both Pyrazinamide CIDAL Yes Intracellular Ethambutol STATIC No Both Streptomycin CIDAL No Extracellular