Clonal Complexity in Mycobacterium tuberculosis Can Hamper Diagnostic Procedures

A Mycobacterium tuberculosis Beijing strain persists at high rates and extends its geographic boundaries 20 years after importation

Transmission of Beijing Mycobacterium tuberculosis can be investigated based on genotypic analysis of clinical isolates. A Beijing strain began to spread on Gran Canaria Island, Spain, at the end of the last century. In 1996, only 3 years after its importation to the island, its frequency had increased to 27.1% of all the isolates. The strain was tracked during the following years, and the most recent data obtained corresponded to 2007-8, when its presence continued to be alarming (21%). In the current study, we updated data on the distribution of this strain 20 years (2013–2014) after it was first detected on the island and extended the analysis for the first time to all the mycobacteriology laboratories covering the population of the Canary Island archipelago. Rapid updating was enabled by means of 2 different strain-specific PCRs: one targeting a peculiar feature of the strain, which was identified based on an IS6110 copy mapping in the Rv2180c gene, and a newly defined strain-specific single nucleotide polymorphism, which was identified by whole-genome sequencing. The results showed that the strain has remained highly prevalent (20.90% of all isolates), has spread throughout the neighbouring islands, and has also reached high representativeness in them (11–32%).

Molecular epidemiology of tuberculosis

The application of genotyping tools allowed us to discriminate between the Mycobacterium tuberculosis isolates obtained in the laboratory. The differentiation between single strains opened the door to molecular epidemiology studies, which had helped us to progress in our knowledge of how this pathogen is transmitted in the progressively more complex socio-epidemiological scenario. The genetic stability of this microorganism led to develop specific methodologies, which are thoroughly revised in this chapter. In addition to their application in epidemiology, we review, how they can offer a response to different diagnostic and clinical challenges. Finally, we focus on describing the novel genomic revolution we are experiencing in the analysis of tuberculosis, the methodology in which it is based and the novel possibilities it offers, including new routes of integrating both the molecular and genomic languages in innovative post-genomic proposals, better suited to our real-life context.