As concerns Dr. Gupta’s questions, of our seven patients who had
persistently positive sputum smears and cultures, two had multiple
drug-resistant disease and another had resistance to isoniazid and was
intolerant of rifampin. Of the four patients with a fully sensitive
organism, two received only isoniazid, rifampin, and pyrazinamide as
initial treatment, and the other two received four drugs initially.
Both patients treated with three drugs initially had radiographic
evidence of cavitation and had either two or three of six lung zones
involved with disease. Whereas it is unlikely that addition of
ethambutal to the initial drug regimen would have hastened smear and
culture conversion, streptomycin may have. Apart from that, we have no
information that would explain the persistent smear and culture
positivity in these patients. We know of no evidence that transient
drug resistance has any clinical relevance.