Genotypic analysis of genes associated with transmission and drug resistance in the Beijing lineage of Mycobacterium tuberculosis

The Beijing genotype of Mycobacterium tuberculosis is an endemic lineage in East Asia that has disseminated worldwide. It is a major health concern, as it is geographically widespread and is considered to be hypervirulent. To elucidate its genetic diversity in Taiwan, phylogenetic reconstruction was performed using 338 M. tuberculosis Beijing family clinical isolates. Region-of-difference analysis revealed the strains from Taiwan to be distributed among six subgroups of a phylogenetic tree. Synonymous single nucleotide polymorphisms at 10 chromosomal positions were also analysed. Among the 338 isolates analysed for single-nucleotide polymorphisms by using mass spectrometry, the most frequent strain found was ST10 (53.3%), followed by ST19 (14.8%) and ST22 (14.5%). Tests of drug resistance showed that the sublineages ST10, ST19 and ST26 were over-represented in the multidrug-resistant population. The presence of mutations in putative genes coding for DNA repair enzymes, which could confer a mutator phenotype to facilitate spreading of the pathogen, did not demonstrate an association with multidrug resistance. Therefore, the DNA repair genes may be involved in transmission but not in drug resistance.