Demonstration of tuberculostearic acid in sputum from patients with pulmonary tuberculosis by selected ion monitoring.

Selected ion monitoring was used to detect tuberculostearic acid (10-methyloctadecanoic acid) in sputum from patients with pulmonary tuberculosis. The specimens were autoclaved, lyophilized, extracted, and methanolysed before being subjected to thin-layer chromatography and injected into the gas chromatograph/mass spectrometer. Tuberculostearic acid could be detected in five of six tuberculous sputum specimens containing acid-fast rods detectable by light microscopy of Ziehl-Neelsen stained smears. After the sputum specimens had been cultured for five days on Löwenstein-Jensen medium, when still no colonies could be observed visually, the presence of tuberculostearic acid was demonstrated in all six cases of tuberculosis. In corresponding analyses of sputum from eight patients with non-tuberculous pneumonia, tuberculostearic acid was not found. This fatty acid, the presence of which was also demonstrated in cultures of various mycobacterial and nocardial species, is characteristic of organisms of the order Actinomycetales. The demonstration of tuberculostearic acid in sputum specimens may constitute a rapid and sensitive way of diagnosing pulmonary tuberculosis.