STRAND DISPLACEMENT AMPLIFICATION AND THE POLYMERASE CHAIN-REACTION FOR MONITORING RESPONSE TO TREATMENT IN PATIENTS WITH PULMONARY TUBERCULOSIS

Specific amplification of Mycobacterium tuberculosis DNA was investiga ted as an alternative to conventional microbiologic follow-up in 31 ca ses of smear- and culture-positive pulmonary tuberculosis, Strand disp lacement amplification (SDA) and the polymerase chain reaction (PCR) w ere applied to 438 sequential sputum specimens: 67 (15%) were positive by culture, 248 (57%) by SDA, and 231 (53%) by PCR (chi(2) = 3.94, P = .05). Of 200 specimens collected > 180 days after treatment started, none yielded positive cultures, while 50 (25%), representing 16 patie nts, were positive by both DNA assays. A weak correlation was demonstr ated between DNA persistence in sputum and duration of culture positiv ity (r = 0.45, P = .01), although no correlation was found with the ra diographic extent of disease, The inability to distinguish live and de ad organisms precludes DNA amplification from use in therapeutic monit oring, For this purpose, quantitative RNA assays are needed if such te chniques are to supplant conventional microbiology.