Genetic diversity of multidrug-resistant Mycobacterium tuberculosis Beijing family isolates in Nepal

Background: Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) poses a major public health problems in developing countries including Nepal. However, multidrug-resistant TB (MDR-TB) is an emerging threat for successful TB control in South Asian countries. Beijing family is a major group of strains contributing to MDR-TB in Nepal similar to other countries. It has been also characterized with high mutability, virulence and speedy transmission features for TB infection comparing than other families. The main purpose of this study was to understand the molecular epidemiological features and transmission dynamics of MDR-TB Beijing family genotype circulating among the Nepalese patients. Methods and materials: A total of 112 MDR-TB Beijing family isolates were analyzed by spoligotyping as described by Kamerbeek et al. (1997). The spoligotyping method could not accurately distinguish the identical pattern of Spoligo-International type (SIT1: deletion of spacer 1–34 and presence of spacer 35–43 in direct repeat locus). Further, genotyping of 112 MDR-TB Beijing family was carried out by spoligotyping and 15 loci mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing as optimized by Wang J et al., (2011). A dendorgram of phylogenetic tree was constructed and also clustering rate analyzed by Bionumerics software. Results: MIRU-VNTR genotyping results showed that 60 isolates had unique patterns, while the remaining 52 isolates were groups into 17 clusters. Furthermore, isolates were classified into three groups based on the phylogenetic i.e. Group I to III contained 4, 93 and 15 isolates respectively. Among Group II contained 93 isolates were further subgroups into A0 to A15. In present study, phylogenetic tree analysis revealed that clustering rate of MDR-TB Beijing family isolates was found at 46.42%. We could not trace out the actual evidence of transmission of TB among the 52 clusters isolates. Conclusion: Our molecular analysis demonstrated that MDR-TB Beijing family was highly diverse in Nepal. Despite of the successful TB control program in Nepal factors associated with increasing prevalence of MDR-TB Beijing family and deeply genomic analysis have not been ascertained. Therefore, present study results could be helpful to enhance epidemiological surveillance, which could leads to implementation of effective control measures against the spread of MDR-TB in Nepal.