Gram stain evaluation of the quality of sputum specimens for mycobacterial culture.

A group of 34 mycobacteria, consisting of 25 Mycobacterium tuberculosis and nine strains of three other species, was isolated from 400 expectorated sputum specimens submitted on 148 patients from county-wide sources. Eight strains (24% of the total) were isolated from specimens evaluated by Gram stain to be oropharyngeal fluids. The remaining 26 strains were isolated from ungradable specimens and those primarily of lower respiratory origin. It was concluded that the random examination of sputum by Gram stain to determine the specimen's quality for mycobacterial isolation is not necessary.