Objective To investigate the prevalence of primary drug-resistant tuberculosis(TB)and associated risk factors in China.We also explored factors contributing to the transmission of multidrug-resistant tuberculosis(MDR-TB).Methods A total of 2794 representative,Mycobacterium tuberculosis isolates from treatment-naive patients were subjected to drug susceptibility testing,and risk factors for drug-resistant TB were analyzed.We also analyzed MDR-TB strain sublineages,drug-resistance-conferring mutations,and risk factors associated with clustered primary MDR strains.Results Among 2794 Mycobacterium tuberculosis isolates from treatment-naive patients,the prevalence of any resistance to first-line drugs was 33.2%and the prevalence of MDR-TB was 5.7%.We did not find any risk factors significantly associated with resistance to first-line drugs.The 93 primary MDR-TB isolates were classified into six sublineages,of which,75(80.6%)isolates were the RD105-deleted Beijing lineage.The largest sublineage included 65(69.9%)isolates with concurrent deletions of RD105,RD207,and RD181.Twenty-nine(31.2%)primary MDR strains grouped in clusters;MDR isolates in clusters were more likely to have S531L rpoB mutation.Conclusion This study indicates that primary drug-resistant TB and MDR-TB strains are prevalent in China,and multiple measures should be taken to address drug-resistant TB. Objective To investigate the prevalence of primary drug-resistant tuberculosis (TB) and associated risk factors in China. We also explored factors contributing to the transmission of multidrug-resistant tuberculosis (MDR-TB). Methods A total of 2794 representative, Mycobacterium tuberculosis isolates from treatment-naive patients were subjected to drug susceptibility testing, and risk factors for drug-resistant TB were analyzed. We also analyzed MDR-TB strain sublineages, drug-resistance-conferring mutations, and risk factors associated with clustered primary MDR strains. Results Among 2794 Mycobacterium tuberculosis isolates from treatment-naive patients, the prevalence of any resistance to first-line drugs was 33.2% and the prevalence of MDR-TB was 5.7% .We did not find any risk factors significantly associated with resistance to first-line drugs.The 93 primary MDR-TB isolates were classified into six sublineages, of which, 75 (80.6%) isolates were the RD105-deleted Beijing lineage.The largest subline age included 65 (69.9%) isolates with concurrent deletions of RD105, RD207, and RD181.Twenty-nine (31.2%) primary MDR grouped in clusters; MDR isolates in clusters were more likely to have S531L rpoB mutation.Conclusion This study indicates that primary drug-resistant TB and MDR-TB are prevalent in China, and multiple measures should be taken to address drug-resistant TB.