Genome analysis shows a common evolutionary origin for the dominant strains of Mycobacterium tuberculosis in a UK South Asian community☆

We have investigated the Mycobacterium tuberculosis strain types present in the South Asian population of the UK, in which tuberculosis is particularly prevalent. In contrast to the widespread Beijing strains which have the variable number tandem repeats (VNTR) profile 42435, isolates with the VNTR profile 42235, jointly with 02335 or 42234 profiles, appear more frequently in tuberculosis patients of South Asian ethnic origin (SA-strains) in the UK than in any other ethnic group. Using microarray-based comparative genomics to distinguish total or partially deleted genes, we found that three of the common deleted regions in the SA-strains were identical to some deleted genes in the strain CH, which caused an outbreak among South Asian patients in Leicester in 2001 but were different from genomic deletions found in Beijing/W strains. Analysis of some of the deleted regions revealed differences in comparison to the strain CH including the polymorphism in some of the PE/PPE and Esat-6 genes, which may be responsible for the diversity of antigenic variation or differences in the activation of the host immune response. Interrupted genes or the replacement by insertion elements was confirmed in some of the deleted genomic regions. Our results are consistent with the hypothesis that the SA-strains may present common features, implying a common origin for this group of strains.