EARLY DETECTION OF MYCOBACTERIUM-TUBERCULOSIS IN BACTEC CULTURES BY LIGASE CHAIN-REACTION

The LCx Mycobacterium tuberculosis ligase chain reaction system (Abbot t Diagnostic Division, Abbott Park, Ill.) was used to detect M, tuberc ulosis in 150 consecutive BACTEC vials on the day on which a positive growth index (GI) was recorded. By LCx, M. tuberculosis DNA was detect ed in BACTEC vials on average 2.6 days before the presence of acid-fas t bacilli could be confirmed by microscopic examination. A total of 10 6 of 108 M. tuberculosis isolates were detected without centrifugation from bottles presenting very low GIs (average, 70; median, 33). No fa lse-positive result was obtained from nontuberculous mycobacteria or f rom isolates,vith contaminants.