We had previously developed a nested polymerase chain reaction (PCR)-immunochromatography
test (ICT) for identification of Mycobacterium tuberculosis (MTB) and differentiation
of MTB from other members of M. tuberculosis complex (MTBC) from clinical sputum samples
(Soo P.C. et al., Journal of Microbiological Methods. 2006, 66(3):440-8.). To further
improve the detection flexibility, simplicity and efficiency, and reduce the cost,
in this study, an alternative molecular diagnosis assay that utilizes gold nanoparticles
derivatized with thiol modified oligonucleotides was developed. The gold nanoparticles
probes, GP-1/GP-2 for IS6110 and GP-3/GP-4 for Rv3618, were designed to specifically
hybridize with target DNAs of MTBC and MTB strains, respectively. Efficacy of the
gold nanoparticle probes assay was evaluated by directly and simultaneously detecting
not only MTBC but also MTB from 600 clinical sputum specimens. Results were compared
with traditional culture and biochemical identification methods together with patients'
clinical assessments. This assay showed a 96.6% sensitivity and 98.9% specificity
towards detection of MTBC, and a 94.7% sensitivity and 99.6% specificity for detection
of MTB. In conclusion, the gold nanoparticle probes assay is a simple, rapid, cost-effective
and accurate detection system and shows great potential in clinical application of
MTBC and MTB detection, especially in developing countries.