Genetic features shared by Mycobacterium tuberculosis strains involved in microevolution events.

Microevolved Mycobacterium tuberculosis (MTB) clonal variants from a parental strain can emerge within a single patient infection and during transmission events. Genotypic rearrangements may involve functional changes conferring advantages to favor strain adaptation to the host. In the present study, we analyzed in depth some genotypic characteristics of a strain with a high tendency to microevolve that generated 6 clonal variants during transmission of sequential hosts. In order to identify genetic features potentially associated to microevolution in MTB, we analyzed 56 3R genes and the IS6110 insertion sites from this strain and identified an SNP in alkA and an IS6110 copy located upstream of a transposase (Rv0755A). These markers could be involved in mechanisms leading to genotypic variation. Both features were shared by strains from our collection that were also involved in microevolution, suggesting their putative association with these events.