Mutations Associated with Pyrazinamide Resistance in the Clinical Isolates of Mycobacterium tuberculosis

Pyrazinamide is one of the four first line drugs for treatment of tuberculosis. It has been widely accepted, that pyrazinamide (PZA) resistance in Mycobacterium tuberculosis is correlated with mutations in the pncA gene. In the present study, pyrazinamide susceptibility was tested in 65 clinical isolates of Mycobacterium tuberculosis by pncA gene sequencing and was then correlated with pyrazinamidase activity. 68% of the resistant isolates showed mutation in the pncA gene which was further correlated with an assay for pyrazinamidase activity

Genotype-phenotype correlates of infantile-onset developmental & epileptic encephalopathy syndromes in South India: A single centre experience

INTRODUCTION: A paucity of literature exists on genotype- phenotype correlates of 'unknown-etiology' infantile-onset developmental-epileptic encephalopathies (DEE) from India. The primary objective was to explore the yield of genetic testing in identifying potential disease causing variants in electro-clinical phenotypes of DEE METHODS: An observational hospital-based study was undertaken on children with unexplained refractory seizure-onset ≤12 months age and developmental delay, whose families consented and underwent genetic testing during a three year time period (2016-2018) by next-generation sequencing (NGS) or multiplex ligand protein amplification. Yield was considered based on demonstration of pathogenic/likely pathogenic variants only and variants of unknown significance (VUS) were documented. RESULTS: Pathogenic/likely pathogenic variants were identified in 26 (31.7 %) out of 82 children with DEE. These included those variants responsible for primarily DEE- 21(76.7 %); neuro-metabolic disorders- 3(18.6 %) and chromosomal deletions- 2(4.7 %). Of these patients, early-infantile epilepsy onset ≤ 6 months age was noted in 22(84.6 %). The DEE studied included Ohtahara syndrome associated with STXBP1 and SCN8A variants with yield of 50 % (2/4 tested); early myoclonic encephalopathy (no yield in 2); West syndrome with CDKL5, yield of 13.3 % (2/15 tested); epilepsy of infancy with migrating partial seizures due to CACNA1A and KCNT1 variants, yield of 67 % (2/3 tested); DEE-unclassified with KCNQ2, AP3B2, ZEB2, metabolic variants (SUOX, ALDH7A1, GLDC) and chromosome deletions (chr 1p36, chr2q24.3); yield of 32 % (8/25 tested). Patients with Dravet syndrome/Dravet-like phenotypes (N = 33) had variants in SCN1A (N = 10), SCN1B, CHD2; yield of 36.4 % (12/33 tested; 57.1 % from NGS). Eighteen patients with potential variants (SCN1A, SCN2A, SCN8A, KCNQ2, ALDH7A1 which also included VUS) could be offered targeted therapy. CONCLUSIONS: Our study confirms a good yield of genetic testing in neonatal and infantile-onset DEE provided robust phenotyping of infants is attempted with prognostic and therapeutic implications, particularly relevant to centres with resource constraints

A Novel Site of Insertion of IS6110 in the moaB3 Gene of a Clinical Isolate of Mycobacterium tuberculosis

In Mycobacterium tuberculosis, genomic variation is generated mainly by insertions and deletions rather than by point mutations. RvD5 is one such deletion in M. tuberculosis H37Rv. Previous studies from our laboratory have shown the presence of moaA3 gene in the RvD5 region in a large number of clinical isolates, that is absent in M. tuberculosis H37Rv and H37Ra. The present study was aimed at investigating the RvD5 locus of the clinical isolates by a detailed PCR analysis. Here we report a new point of insertion of the mobile genetic element, IS6110 in the genome of one clinical isolate of M. tuberculosis. The insertion has disrupted the moaB3 gene, one of the ORFs in the RvD5 region, which is involved in the molybdopterin biosynthetic pathway. This insertion of IS6110 in the moaB3 of the clinical isolate is different when compared to the insertion in the moaB3 gene of M. tuberculosis H37Rv where 4kb RvD5 region has been lost by homologous recombination and only a truncated form of the gene is present. This finding is of relevance since IS6110 is a major element determining the genome plasticity of M. tuberculosis and its numerical and positional polymorphism has always been of special interest