Mycobacterium tuberculosis
World Tuberculosis Day on 24 March recognises the date in 1882 when Dr Robert Koch announced his discovery of Mycobacterium tuberculosis, the bacillus that causes tuberculosis (TB). In celebration of this, we are excited to present a collection of recently published papers on M. tuberculosis.
Collection Contents
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Pyrosequencing: a rapid and effective sequencing method to diagnose drug-resistant tuberculosis
Purpose. This study was undertaken to evaluate the efficiency of the pyrosequencing (PSQ) assay for the rapid detection of resistance to rifampicin (RIF), fluoroquinolones (FQs) and second-line injectables (SLIs) such as capreomycin (CAP) and kanamycin (KAN) in Mycobacterium tuberculosis (Mtb) clinical isolates.
Methodology. Pyrosequencing is a simple and accurate short read DNA sequencing method for genome analysis. DNA extraction from Mtb clinical isolates was performed using Tris-HCl buffer and chloroform. The rpoB (RIF), gyrA (FQs) and rrs (aminoglycosides) genes were amplified, followed by sequencing using the PyroMark Q24 ID system. The PSQ results were compared with the results from the conventional drug susceptibility testing performed in the laboratory.
Results. The sensitivity of the PSQ assay for the detection of resistance to RIF, FQ, CAP and KAN was 100 %, 100 %, 40 % and 50 %, respectively. The specificity of the PSQ assay was 100 %.
Conclusion. The PSQ assay is a rapid and effective method for detecting drug resistance mutations from Mtb clinical isolates in a short period of time.
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Phylogenomic analysis of the species of the Mycobacterium tuberculosis complex demonstrates that Mycobacterium africanum, Mycobacterium bovis, Mycobacterium caprae, Mycobacterium microti and Mycobacterium pinnipedii are later heterotypic synonyms of Mycobacterium tuberculosis
The species within the Mycobacterium tuberculosis Complex (MTBC) have undergone numerous taxonomic and nomenclatural changes, leaving the true structure of the MTBC in doubt. We used next-generation sequencing (NGS), digital DNA–DNA hybridization (dDDH), and average nucleotide identity (ANI) to investigate the relationship between these species. The type strains of Mycobacterium africanum , Mycobacterium bovis , Mycobacterium caprae , Mycobacterium microti and Mycobacterium pinnipedii were sequenced via NGS. Pairwise dDDH and ANI comparisons between these, previously sequenced MTBC type strain genomes (including ‘Mycobacterium canettii’, ‘Mycobacterium mungi’ and ‘Mycobacterium orygis’) and M. tuberculosis H37RvT were performed. Further, all available genome sequences in GenBank for species in or putatively in the MTBC were compared to H37RvT. Pairwise results indicated that all of the type strains of the species are extremely closely related to each other (dDDH: 91.2–99.2 %, ANI: 99.21–99.92 %), greatly exceeding the respective species delineation thresholds, thus indicating that they belong to the same species. Results from the GenBank genomes indicate that all the strains examined are within the circumscription of H37RvT (dDDH: 83.5–100 %). We, therefore, formally propose a union of the species of the MTBC as M. tuberculosis . M. africanum , M. bovis , M. caprae , M. microti and M. pinnipedii are reclassified as later heterotypic synonyms of M. tuberculosis . ‘M. canettii’, ‘M. mungi’, and ‘M. orygis’ are classified as strains of the species M. tuberculosis . We further recommend use of the infrasubspecific term ‘variant’ (‘var.’) and infrasubspecific designations that generally retain the historical nomenclature associated with the groups or otherwise convey such characteristics, e.g. M. tuberculosis var. bovis.
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