Abstract
Background: To investigate the spread of specific genotypes in a defined geographical area and to determine any relationship of these genotypes with drug resistance the most essential method is molecular typing. It allows a rapid and precise species differentiation.
 Objective: This study was intended to observe the genotypes of XDR mycobacterium tuberculosis by determining 24 loci MIRU-VNTR analysis.
 Methods: To gain an insight about molecular typing of MTB and drug resistance-associated mutations in XDR-TB isolates a total of 98 multi drug 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 http://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 (54.60%) XDR-TB isolates belonged to Beijing strain, Other MTB strain also detected were Delhi/CAS two(18.20%), Haarlem two(18.20%) and New-1, one (9.10%) 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.
 Bangladesh Med Res Counc Bull 2020; 46(1): 22-28
Highlights
Tuberculosis (TB) is a major public health problem in Bangladesh
XDR-TB is the result of an adverse treatment outcome of multidrug resistant tuberculosis (MDR-TB); many cases are never diagnosed due to limitations in laboratory capacity to test for second-line drug resistance.[3]
Microscopy, DNA extraction and second line line probe assay (LPA) was done in National Tuberculosis Reference Laboratory (NTRL) and 11 XDR-TB were identified. 24 loci MIRUVNTR typing of 11 XDR-TB isolates were performed at Department of Microbiology and Immunology, Bangabandhu Sheikh Mujib Medical University (BSMMU)
Summary
Tuberculosis (TB) is a major public health problem in Bangladesh. The estimated number of all forms (new and relapse) TB cases were 221 per 100 000 population in 2017. The incidence of Multi drug resistant (MDR-TB) was 5.1/100,000 population. Drug resistant tuberculosis (XDR-TB) is defined as TB resistant to Rifampicin (RMP) and Isoniazid (INH) with additional resistance to second line anti-TB drugs i.e. to any fluoroquinolones (FQs), and to at least one of the three injectable second-line drugs (ISL) naming amikacin (AMK), kanamycin (KAN) and capreomycin (CAP).[2] The prevalence of XDRTB is 8.5% worldwide.[1] XDR-TB is the result of an adverse treatment outcome of MDR-TB; many cases are never diagnosed due to limitations in laboratory capacity to test for second-line drug resistance.[3] Treatment of XDR-TB patients is more challenging and less successful than that of Extended Drug Resistance TB Isolates patients with other types of TB.4An extremely high death rate from XDR-TB was reported in patients co-infected with HIV in South Africa.[5]. 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
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