Culture of Mycobacterium tuberculosis from non-fixed sputum smears

Smears prepared from sputum species were kept in the dark at 4 degrees C or at 20-25 degrees C. Cultures for mycobacteria were carried out on these smears 0, 4, 8, and 15 days later and the results compared with those of cultures made from the sputum specimen on the day of collection. The percentage of negative cultures from originally positive specimens was high, and use of the method is not considered advisable. There is an additional risk of infection for laboratory staff when handling unfixed smears.