Early detection of Mycobacterium tuberculosis in BACTEC cultures by ligase chain reaction

Ill.) was used to detect M. tuberculosis in 150 consecutive BACTEC vials on the day on which a positive growth index (GI) was recorded. By LCx, M. tuberculosis DNA was detected in BACTEC vials on average 2.6 days before the presence of acid-fast bacilli could be confirmed by microscopic examination. A total of 106 of 108 M. tuberculo-sis isolates were detected without centrifugation from bottles presenting very low GIs (average, 70; median, 33). No false-positive result was obtained from nontuberculous mycobacteria or from isolates with contaminants. Rapid diagnosis of tuberculosis is an important component of measures to control the disease (13), which is an objective made more urgent by the appearance of multidrug-resistant strains (7). Nucleic acid amplification techniques, which allow detection of Mycobacterium tuberculosis directly from samples in a matter of hours, apparently represent the ultimate answer to this issue. They lack sensitivity for smear-negative specimens, and their use is generally restricted to selected samples. Culture remains the only mycobacterial investigation performed, alon