Novel approaches in diagnosing tuberculosis

Abstract

The WHO declared tuberculosis (TB) a global emergency. An estimated 8-9 million new cases occur each year with 2-3 million deaths. Currently, TB is diagnosed mostly by chest-X ray and staining of the mycobacteria in sputum with a detection limit of 1x10 4 bacteria /ml. There is an urgent need for better diagnostic tools for TB especially for developing countries. We have validated the electronic nose from TD Technology for the detection of Mycobacterium tuberculosis by headspace analysis of 284 sputum samples from TB patients. We used linear discriminant function analysis resulting in a sensitivity of 75% a specificity of 67% and an accuracy of 69%. Further research is still required to improve the results by choosing more selective sensors and sampling techniques.We used a fast gas chromatography-mass spectrometry method (GC-MS). The automated procedure is based on the injection of sputum samples which are methylated inside the GC injector using thermally assisted hydrolysis and methylation (THM-GC-MS). Hexacosanoic acid in combination with tuberculostearic acid was found to be specific for the presence of M. tuberculosis. The detection limit was similar to microscopy. We found no false positives, all microscopy and culture positive samples were also found positive with the THM-GC-MS method. The detection of ribosomal RNA from the infecting organism offers great potential since rRNA molecules outnumber chromosomal DNA by a factor 1000. It thus may possible to detect the organism without amplification of the nucleic acids (NA). We used a capture and a tagged detector probe for the direct detection of M. tuberculosis in sputum. So far the detection limit is 1x10 6 bacteria / ml. Currently we are testing a Lab-On-A-Chip Interferometer detection system. The World Health Organization (WHO) declared tuberculosis (TB) a global emergency. It is estimated that 1/3rd of the World's population is infected with Mycobacterium tuberculosis (M. tuberculosis). An estimated 8-9 million new cases occur each year with 2-3 million deaths. The majority of cases occur in sub-Saharan Africa, South and Southeast Asia, Latin America and the Caribbean. The recent increase in TB is related to the increase in HIV infections.WHO global targets are 70% detection rate of estimated smear positive TB patients and a cure rate of 85%. The WHO launched the STOP TB program, Direct Observed Treatment Short course (DOTS). The DOTS program alone is incapable of reducing the TB burden because the detection rate of 70% is not reached in many high burden countries. In 2006 overall case detection was 60% (confidence interval 52-69%; treatment success was 84%. Both targets were achieved in the Western Pacific Region, and treatment success exceeded 85% in the South-East Asia region.Early diagnosis of TB followed by appropriate treatment will reduce the burden of TB. Currently, TB is diagnosed by chest X-ray, staining of the mycobacteria in sputum after Ziehl-Neelsen staining (ZN), culture and nucleic acid amplification techniques. These methods are not sati...