Genomic sequence based scanning for drug resistance-associated mutations and evolutionary analysis of multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis.
OBJECTIVE
To better understand the molecular mechanisms and evolution of drug resistance in Mycobacterium tuberculosis (M. tuberculosis), we performed a genomic sequence based scanning of drug resistance-associated loci for multidrug-resistant (MDR) and extensively drug-resistant (XDR) M. tuberculosis strains.


METHODS
Forty-five pairs of primers covering known drug resistance-associated loci compiled in the TBDReaMDB database were designed to perform the analysis of drug resistance-associated mutations for 14 M. tuberculosis clinical isolates from TB patients in China. Genetic diversity and evolutionary analysis was done using concatenated nucleotide sequences of drug resistance-associated loci.


RESULTS
Forty-four types of mutations were identified in 14 M. tuberculosis clinical isolates. Average nucleotide diversity for drug resistance-associated loci increased in the M. tuberculosis isolates as the drug resistance increased (π = 0, π = 0.00021, and π = 0.00028 for susceptible, MDR, and XDR isolates, respectively). The dN/dS ratios for coding regions of drug resistance-associated genes in MDR and XDR isolates were 2.73 and 1.83, respectively. MDR and XDR isolates were distributed sporadically on different branches in the phylogenetic trees.


CONCLUSIONS
Our study provides supporting evidence to demonstrate that the MDR- and XDR-M. tuberculosis strains have evolved independently driven by positive selection.
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, No. 8 North 2 Zhongguancun Road, Haidian District, Beijing 100019, China. liucuihua@im.ac.cn
Cui Hua
CH
Liu
Hong Min
HM
Li
Na
N
Lu
Qi
Q
Wang
Yong Liang
YL
Hu
Xi
X
Yang
Yong Fei
YF
Hu
Patrick C Y
PC
Woo
George F
GF
Gao
Baoli
B
Zhu
D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000032:analysis; D030541:Databases, Genetic; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D019143:Evolution, Molecular; D054908:Extensively Drug-Resistant Tuberculosis / Q000382:microbiology*; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D010802:Phylogeny; D018088:Tuberculosis, Multidrug-Resistant / Q000382:microbiology*
D004269:DNA, Bacterial