To prevent the spreading of tuberculosis, it is necessary to have efficient and prompt methods of detection of the causative agent. Recently, only molecular methods provide rapid (less than 24 h) detection of M.tuberculosis with simultaneous determination of pathogen susceptibility to anti-TB drugs. Among existing molecular methods, hydrogel-based biological microchips (biochips) developed at Engelhardt Institute of Molecular Biology proved to be a reliable diagnostic tool.
The biochip used in the system TB-BIOCHIP MDR contains oligonucleotide probes for the detection of IS6110 sequence, as well as probes for the detection of mutations in the gene rpoB responsible for resistance to rifampin and in the genes katG, inhA, and ahpC, which cause resistance to isoniazide. The procedure of genome analysis of the TB causative agent using the method is based on hybridization of amplified fluorescently labeled fragments of the aforementioned genes with sets of complementary probes immobilized on biochips.
In the Russian Federation, the TB-BIOCHIP MDR test underwent appropriate certification and was included in routine laboratory diagnostics. It has been used successfully by more than twenty anti-TB institutions. A total of more than 20,000 clinical samples were analyzed with the reported sensitivity between 89.5 and 96.9% for rifampin and 82.1 and 89.3% for isoniazid and reported specificity ranging from 86.2 to 94.3% for rifampin and from 88.0 to 95.1% for isoniazid.
Early identification of pathogen susceptibility to rifampin and isoniazid using TB-biochips results in a significantly better tretment outcome because of the introduction of adequate drug therapy at the earliest stages of treatment. The TB-BIOCHIP MDR test identifies more mutations responsible for resistance to rifampicin and isoniazid than any other commercially available test. Computerized registration and processing of the results yield unambiguous conclusions, excluding human error.
Another system TB-BIOCHIP FQ allows detection of mutations in the gyrA gene responsible for resistance to fluoroquinolones (FQ). Using TBBIOCHIP FQ system it was shown that the proportion of patients with resistance infection did not exceed 2% among newly diagnosed TB cases, whereas this proportion was 10% or even more among chronic patients with already identified multidrug-resistant disease. The sensitivity and specificity of the “TB-Biochip FQ” test was determined in clinical trials and reached 81 and 96%, respectively.
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