Tuberculosis: new type of test rapidly and clearly detects resistance

© FZ Borstel/Pukall

An international team managed by scientists at the Research Center Borstel and the German Center for Infection Research (DZIF) have examined a new method for detecting resistant tuberculosis strains more quickly and therefore treating them more effectively. The study demonstrated that the so-called Deeplex®-MycTB test delivers very promising results and could play an important role in diagnostics in the future.

With ten million new infections each year, tuberculosis is one of the deadliest infectious diseases in the world. Particularly multidrug-resistant mycobacterium strains make it difficult to keep tuberculosis under control around the globe and require extensive resistance profiles to be identified quickly before effective and personalised treatment can begin.

Detecting resistance based on the growth of the bacteria is very time-consuming and can take up to six weeks. While available molecular biological tests can be performed on clinical material, they can only collect a limited number of resistance variants. An excellent alternative to extensive resistance detection is analysing the genome of the pathogens by so-called “whole genome sequencing”. However, direct sequencing from clinical material is challenging because the quantity of mycobacterial DNA is low.  

Therefore, this study tested a variant in which only areas of the genome directly associated with resistance are replicated and then decoded. This approach was pursued with the test by the company Genoscreen (Lille, France). It involves a new kind of “deep sequencing assay” that covers 18 resistance-associated regions in the mycobacterial genome. 

The comparison of Deeplex®-MycTB data with typical whole genome sequence data showed 98 % concordance, and the comparison with phenotypical resistance data showed > 95 % concordance for the first-line drug and between 70 and 100 % concordance for the second-line drug. The concordance of only 70 % with the fluoroquinolone antibiotics is due to variants that show a so-called “low-level” resistance and only occur in a small percentage in the analysed sample. The new Deeplex®-MycTB test is able to detect these variants, whereas phenotypic tests are often limited. 

“The results of this study illustrate that the Deeplex®-MycTB test is an ideal tool to quickly and extensively detect resistance from clinical samples and can replace phenotypic resistance detection for the majority of diagnostic samples in the future,” says Dr Silke Feuerriegel, lead author of the study and DZIF scientist at the Research Center Borstel.

Source: Press release FZ Borstel

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