Mycobaterial interspersed repetitive units-Variable number of tandem repeats analysis and pattern of drug resistance in extended drug resistant TB isolates from pulmonary tuberculosis patients in Bangladesh

Abstract

Background: Tuberculosis including multidrug resistance is a major public health problem in Bangladesh. Result of an advance treatment outcome of multidrug resistance is extended drug resistance tuberculosis. Objective: This study was intended to observe the genotypes of XDR mycobacterium tuberculosis by determining 24 loci MIRU-VNTR analysis. Methods: A total of 98 multidrug resistant tuberculosis (MDR-TB) isolates collected through Xpert MTB/RIF assay. They were subjected to 2nd line (Fluoroquinolones, kanamycin, capreomycin and amikacin) drug susceptibility testing through line probe assay (LPA) in a view to detect extensively drug resistant tuberculosis (XDR-TB). Genotyping was done for XDR-TB isolates using 24 loci Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) using the online tool at www.MIRU-VNTRplus.org.. Out of 98 MDR-TB isolates 11(11.23%) XDR-TB isolates were typed and analysed. Results: Twenty four loci MIRU-VNTR genotyping involving similarity searching and phylogenetic tree analysis revealed that six (54.6%) XDR-TB isolates belonged to Beijing strain, other MTB strain also detected were Delhi/CAS two(18.2%), Haarlem two (18.2%) and New-1, one (9.1%) in number. Minimum spanning tree analysis showed two strain of Beijing family form a clonal complex. Beijing strains were more common among younger age group and within urban population. Beijing strains were also predominant in treatment failure patient. Only one new case of XDR-TB belongs to Delhi/CAS family. Second line mycobacterial drug resistance (MTBDRsl) detected by LPA showed the most prevalent mutations involved in fluoroquinolones drug resistance (FQ) was Asp94Gly in gyrA gene (54.55%) in quinolone resistance determining region (QRDR) and for injectable 2nd line drug resistance (ISL) was A1401G, C1402T in 16S rrs gene (100%).. All XDR-TB isolates showed resistance to levofloxacin in 2nd line LPA but moxifloxacin showed low level resistance to some cases. Conclusion: Molecular typing of XDR- TB isolates and pattern of drug resistance associated mutations in XDR-TB isolates in Bangladesh have not been reported previously. The result of this study highlights the need to reinforce the TB policy in Bangladesh with regard to control the spread and transmission as well as detection and treatment strategies regarding XDR-TB.