A major subgroup of Beijing family Mycobacterium tuberculosis is associated with multidrug resistance and increased transmissibility.

This study investigated further the association between the Beijing family Mycobacterium tuberculosis circulating in rural China and anti-tuberculosis (TB) drug resistance. In total, 351 M. tuberculosis isolates were collected through a population-based epidemiological study, 223 (63·5%) of which were resistant to at least one anti-TB drug, including 53 (15·1%) multidrug-resistant (MDR) isolates. Spoligotyping found 243 isolates (69·2%) that belonged to the Beijing family. A major subgroup of the Beijing family identified by mycobacterial interspersed repetitive unit (MIRU) genotyping (223325173533), showed significantly higher frequencies of MDR (44·7% vs . 13·7%, OR 6·18, 95% CI 2·68–14·23), katG and rpoB mutations (31·6% vs . 9·3%, OR 4·27, 95% CI 1·86–9·80), and being clustered by IS 6110 RFLP genotyping (60·5% vs . 21·0%, OR 6·14, 95% CI 2·82–13·37) in comparison with other Beijing family isolates. Our data suggest that MIRU genotype 223325173533 of the Beijing family is associated with MDR and increased transmissibility.