Fast plaque assay technique for detection of mycobacterium tuberculosis in sputum samples of newly diagnosed cases of pulmonary tuberculosis

ABSTRACT

Tuberculosis [TB] is a serious public health problem that especially prevalent in developing countries. An essential element in the control of TB is the rapid, sensitive and specific identification of the causative agent. Mycobacteriophages constitute a potentially useful approach for detecting viable Mycobacterium tuberculosis bacilli as well as for susceptibility studies. The aim of this study is to evaluate the diagnostic value of the Phage Tek MB kit for pulmonary tuberculosis in comparison with standard Lowenstein-Jensen [LJ] media and staining techniques for respiratory specimens. Sputum specimens submitted for diagnosis of mycobacterial disease at Ain Shams University hospital from August to November 2004 were included in the study. Specimens were studied using both of the conventional methods [direct microscopic examination and culture in LJ medium] and the Phage Tek MB assay. The sensitivity, specificity, positive and negative predictive value for the FAST Plaque TB assay relative to that of culture were 65.52, 100, 100 and 52.38%, respectively. The sensitivity was much higher in smear positive samples in comparison to smear negative ones [73.91% and 33.33%, respectively]. FAST Plaque TB proved to be specific, and rapid. It is able to detect M. tuberculosis in clinical samples within 1 day with 100% specificity, long before culture results]. Also it is cheap technology in comparison to PCR and would be suitable for use by routine microbiology laboratories, especially in developing countries