Survival of tubercle bacilli in heat-fixed sputum smears.

Tubercle bacilli, which survived heat fixation, were detected with a slide culture technique which allowed the entire smear to be examined. Both conventional flame fixation and the use of a controlled hot-plate failed to render tuberculous sputum smears safe for further handling. Smears which were stained with the phenol-auramine method failed to yield growth on culture. If delay between preparation and staining is unavoidable, it is recommended that smears are given additional treatment to prevent the survival of tubercle bacilli.