Utility of Gram's and Giemsa stains in the diagnosis of pulmonary tuberculosis.

Conflicting information in the literature regarding the staining properties of Mycobacterium tuberculosis using Gram's stain and experience in two patients with pulmonary tuberculosis in whom the diagnosis was suspected after staining with non-acid-fast bacillus stains prompted the study of Gram's stain in this disease. The main finding was that mycobacteria appear as refractile, gram-neutral, or faintly gram-positive bacilli after Gram's stain, depending upon the plane of focus in which the organisms are regarded. It is concluded that the diagnosis of mycobacterial disease may be suggested by Giemsa- and Gram-stained smears of clinical specimens. M. tuberculosis may be either gram-neutral or gram-positive.