Suitability of IS6110 based polymerase chain reaction for the detection of Mycobacterium tuberculosis in sputum of new pulmonary tuberculosis cases

Abstract

Background and Objectives: Early diagnosis of pulmonary tuberculosis (PTB) is one of the primary challenges in curtailing its spread. Nucleic acid amplification methods targeting Mycobacterium tuberculosis (MTB) sequences in clinical specimens are increasingly in use as a tool for early tuberculosis (TB) diagnosis. Insertion sequence 6110, specific for MTB complex was targeted in sputum of new pulmonary TB patients in the present study, to determine its suitability for rapid diagnosis. Materials and Methods: A total of 100 new symptomatic for PTB attending a teaching hospital between January 2008 and December 2010 were enrolled in this study. Satisfactory sputum sample from all symptomatic was processed for microscopy by Ziehl-Neelsen (ZN) method, culture on Lowenstein-Jensen medium and polymerase chain reaction (PCR) for the IS6110 element. Results: Concordance among three methods was 87% and discordance in 13%. Positivity by ZN, culture, and PCR was 29%, 35%, and 35%, respectively. PCR picked up additional five cases, which were negative by both smear and culture. Excluding samples which grew MTB isolates lacking IS6110 the sensitivity of target IS6110 was found to be 100% with respect to ZN microscopy and culture. Interpretation and Conclusions: PCR targeting IS6110 in sputum was found to be very sensitive and specific in the rapid diagnosis of new PTB cases.

Keywords

• IS6110 Mycobacterium tuberculosis
• polymerase chain reaction
• pulmonary tuberculosis