comparative study on use of nested pcr and conventional methods in diagnosis of treated and untreated tuberculosis

a nested polymerase chain reaction (pcr) assay with two pairs of primers was applied for the detection of m. tuberculosis complex dna in specimens of 51 patients. of these, 31 clinically diagnosed patients (group i) recruited from july 1996 to june 1997 were given antituherculous chemotherapy from one to six months with standard daily regimen (isaniazid, 5 mg/kg; rifampin, 10 mg/kg; pyrazinamitle, 25 mg/kg., and either ethambutol or streptomycin, 15 mglkg) and returned for subsequent testing. other 20 persons (group ii) were untreated patients suspected of tuberculosis. 24 patients from group i were found to harbor m. tuberculosis before treatment, however, mycobacterial cultures were recovered from specimens of only two patients after treatment. m. tuberculosis complex dna could he pcr delected in initial specimens from 26 patients, while 2 months after initiation of the therapy, pcr yielded positive results in specimens obtained from three of them, suggesting incomplete treatment. of 42 cumulated specimens from patients of both groups that groan culture, 41 had positive results on pcr closely matching to that of culture testing. of other 40 specimens that produced no m. tuberculosis complex colonies, seven were found to be pcr-positive. however, there was a specimen from treated patient which had negatie result on pcr being positive by conventional tests. these results indicate that the pcr assay is highly sensitive and allows for the effective control of the efficacy of antituherculous chemotherapy in patients.