Abstract: Objective To initially ascertain molecular characteristics of the second-line antituberculosis drug-resistant M. tuberculosis clinical isolates in Jiangxi, and to evaluate the feasibility of multiplex allele-specific polymerase chain reaction (MAS-PCR) assay for the detection of the second-line drug resistance in M. tuberculosis clinical isolates.  Methods Fifty-two second-line drug-resistant isolates and 30 pan-susceptible isolates from Jiangxi province were analyzed for gene mutations related to the second-line drug resistance using MAS-PCR and DNA sequencing.  Results DNA sequencing indicated that 32 of 39 ofloxacin （Ofx）-resistant isolates displayed missense mutations in gyrA gene, and the most common mutations were observed at codon 94 (n=27)，and only 2 isolates showed single-point mutation in gyrB gene. In addition, 22 of 29 kanamycin (Km)- or capreomycin (Cm)-resistant isolates had an A-to-G transition at nucleotide position 1401 of rrs gene. It is shown that the Beijing genotype was predominant (76.92%, 40/52) among the 52 drug-resistant strains. Of 40 Beijing genotype strains, 17 strains （42.50%）displayed gyrA-GAC94GGC mutations, and 19 strains (47.50%) showed rrs-A1401G mutations. No relationship could be demonstrated between Beijing genotype and gyrA-GAC94GGC or rrs-A1401G mutations（χ²=1.16，1.92，P value＞0.05）. In comparison with the phenotypic data, the sensitivities of the detection of Ofx resistance, and Km or Cm resistance using MAS-PCR were 61.54%（24/39）and 79.31%（23/29） respectively. Conclusion In Jiangxi province, gyrA mutation is the main molecular mechanism of Ofx resistance in M. tuberculosis, and an A1401G mutation in the rrs gene is the main cause of Km or Cm resistance. MAS-PCR, an assay with technical simplicity, short turnaround time, and low cost, could be useful for screening second-line drug-resistant M. tuberculosis, particularly in resource-limited areas with a high prevalence of tuberculosis and drug resistance.

Key words: Mycobacterium tuberculosis, Drug resistance, bacterial, Antibiotics, antitubercular, Kanamycin, Capreomycin sulfate, Polymerase chain reaction, Jiangxi