Genome sequencing of 161 Mycobacterium tuberculosis isolates from China identifies genes and intergenic regions associated with drug resistance

Lijun Bi and colleagues report sequencing of 161 tuberculosis strains from China, including 44 drug-sensitive, 94 MDR and 23 XDR isolates. They identify 72 new genes and 28 new intergenic regions significantly associated with drug resistance. The worldwide emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis threatens to make this disease incurable 1 , 2 . Drug resistance mechanisms are only partially understood 3 , 4 , 5 , and whether the current understanding of the genetic basis of drug resistance in M. tuberculosis is sufficiently comprehensive remains unclear. Here we sequenced and analyzed 161 isolates with a range of drug resistance profiles, discovering 72 new genes, 28 intergenic regions (IGRs), 11 nonsynonymous SNPs and 10 IGR SNPs with strong, consistent associations with drug resistance. On the basis of our examination of the dN/dS ratios of nonsynonymous to synonymous SNPs among the isolates 6 , 7 , 8 , we suggest that the drug resistance–associated genes identified here likely contain essentially all the nonsynonymous SNPs that have arisen as a result of drug pressure in these isolates and should thus represent a near-complete set of drug resistance–associated genes for these isolates and antibiotics. Our work indicates that the genetic basis of drug resistance is more complex than previously anticipated and provides a strong foundation for elucidating unknown drug resistance mechanisms.