Vipul Sharma

Typing of drug resistant isolates of Mycobacterium tuberculosis from India using the IS6110 element reveals substantive polymorphism

We investigated IS6110 polymorphism in clinical isolates of Mycobacterium tuberculosis from patients attending the outpatient department at various hospitals in northern India. DNA fingerprinting of 126 clinical isolates of M. tuberculosis was carried out using restriction fragment length polymorphism (RFLP) associated with the IS6110 element in M. tuberculosis genomes. A substantive degree of polymorphism was evident in the MDR M. tuberculosis isolates. The number of bands in the fingerprints varied from 0 to 19. However, the lack of common bands made it difficult to cluster the majority of these isolates. We were also unable to associate drug resistance with IS6110 copy number. Specific regions of the gyrA and katG genes from a representative number of these isolates were sequenced to determine the genotype. The majority of the isolates analyzed were found to belong to Group 1, indicating that these strains were evolutionarily older. We find no evidence of the W strain, prevalent in the US, in our study. The epidemiological patterns of the various strains in India seem to be very complex, as reflected by the presence of a large number of different strains (types) within north India.

Role of embCAB gene mutations in ethambutol resistance in Mycobacterium tuberculosis isolates from India

In the present study, ethambutol (EMB) resistance-associated mutations were characterised in the embCAB genes of clinical isolates of Mycobacterium tuberculosis (MTB) collected in India. Thirty MTB isolates were tested for their susceptibility to first-line antitubercular drugs using the Löwenstein-Jensen proportion method, and EMB minimum inhibitory concentrations of MTB isolates were determined by the resazurin microtitre assay. Sequencing of various regions of the embCAB genes was performed to identify EMB resistance-associated mutations. Mutations of embB306 were detected in 15 of 23 EMB-resistant MTB isolates. Three EMB-resistant isolates had mutations at codon 270 of the embC gene, two of which also harboured embB306 mutations. No mutation was identified in the embA gene. All seven EMB-sensitive MTB isolates had the wild-type embCAB sequence. In summary, embB306 mutations were associated with EMB resistance, and mutation at codon 270 of the embC gene may contribute to high-level EMB resistance in some MTB isolates.

Metamaterials in microwave applications: A selective survey

Recently, metamaterial has grabbed prime focus of research fraternity working in the field of antennas, microwave filters and components design. Many different structures of split ring resonators (SRR) for their respective applications have been reported till date. In all of these findings in some way or other, using metamaterial, drastic reduction in size of the component has been achieved. Thus, the metamaterial can be viewed as a powerful miniaturization tool in the field of radio frequency (RF) and microwave. Since its inception in 1999, many variants of SRR have come up leading to more efficient designs with better RF properties. This review paper presents an application based review of such variants and will be useful for new researchers exploring its use in their research problems.