High-resolution genotyping of Mycobacterium tuberculosis isolates from syria using mycobacterial interspersed repetitive unit-variable-number tandem repeat

Abstract

Background: We aimed to evaluate the utility of 24 loci mycobacterial interspersed repetitive unit-variable-number tandem repeat (MIRU-VNTR) genotyping method for discrimination of clinical Mycobacterium tuberculosis isolates in Syria. Methods: We studied 68 clinical tuberculosis (TB) isolates originating from unrelated Syrian TB patients from different regions in Syria. Genetic types (consisting of 24 digits) were determined and used to construct a dendrogram. Results: Fifty-six distinct MIRU patterns were revealed, from which 52 patterns were represented by unique isolates. Sixteen isolates were distributed into 4 clusters, 3 of which consisted of isolates belonging to the TUR lineage. Nine MIRUs showed high Hunter-Gaston index (HGI) values (>0.6), with QUB-26 having the highest discriminatory power (HGI = 0.821), followed by MIRU10, MIRU26, MIRU16, and Mtub39. The cumulative HGI value of the 24-MIRU set was 0.985. Interestingly, using the reduced 15-MIRU, set resulted in the same HGI. The TUR lineage was the most frequent in our sample (23.5%), and it appears that it is widespread in Syria as in Turkey. The discriminatory power of MIRU-VNTR among the subset belonging to the TUR lineage was extremely low due to the high clustering rate (62.5%) of TUR isolates, indicating that this method is inappropriate to discriminate isolates of this lineage. On the other hand, the Beijing lineage was not represented in our isolates. Conclusion: We demonstrated the high prevalence of the TUR lineage and the low prevalence of the Beijing lineage among Syrian clinical TB isolates. The MIRU-VNTR method was highly discriminative among non-TUR TB isolates, but it was inappropriate to discriminate isolates of the TUR lineage.