Abstract
The aim of this study was to investigate the usefulness of combining profiles obtained by using a line probe assay (LPA) originally intended to characterize the resistance of two major anti-tuberculosis drugs to the association of spoligotyping and MIRU-VNTR, in order to improve its discriminatory power. For this purpose, 74 strains of Mycobacterium tuberculosis belonging to the same cluster after spoligotyping were further typed by using the 24 loci MIRU/VNTR. These strains were then tested by the GenoType MTBDRplus, and profiles obtained were analyzed within previously obtained clusters. The combination of spoligotying and MIRU-VNTR led to the consolidation of 56 of them (75.7%) in 9 clusters. Most of the strains (54, 96.4%) were multidrug resistant (MDR). From the 9 initial clusters, the addition of GenoType MTBDRplus helped to define 26 profiles including 11 unique profiles, and 3 original clusters remained undifferentiated. Results obtained express the relevance of combining this method which improved quite significantly the discriminatory power in typing Mycobacterium tuberculosis.
Highlights
Molecular methods used to type isolates belonging to Mycobacterium tuberculosis complex (MTBc) are relevant in both phylogenetic and epidemiological studies [1]
In addition to conventional typing methods, there are drug resistance genotyping tests based on line probe assays (LPAs) which were endorsed by the World Health Organization [4] and can be widely used
While 9 clusters were previously defined after the combination of spoligotyping and MIRU-VNTR, 27 profiles were described after adding GenoType MTBDRplus
Summary
Molecular methods used to type isolates belonging to Mycobacterium tuberculosis complex (MTBc) are relevant in both phylogenetic and epidemiological studies [1]. Because of the limited discriminatory power of classical genotyping methods such as Spoligotyping, MIRU-VNTR and IS6110-RFLP, analyses of SNPs and whole genome sequencing (WGS) have recently begun to be used in epidemiological investigations for instance to identify outbreaks [2] [3]. In addition to conventional typing methods, there are drug resistance genotyping tests based on line probe assays (LPAs) which were endorsed by the World Health Organization [4] and can be widely used. By detecting a large number of mutations involved in resistance to anti-tuberculosis drugs, they can generate a broad range of patterns. Even if all pansusceptible strains by these methods display the same pattern, the putative number of possible combinations for resistant and in particular multidrug resistant (MDR) strains can be relatively substantial
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