Characterisation of drug resistance-associated mutations among clinical multidrug-resistant Mycobacterium tuberculosis isolates from Hebei Province, China.

OBJECTIVES

Multidrug-resistant tuberculosis (MDR-TB) is a major public-health problem in China. However, there is little information on the molecular characterisation of clinical MDR-TB isolates in Hebei Province.

METHODS

In this study, 123 MDR-TB isolates were identified in sputum cultures using traditional drug susceptibility testing. The isolates were analysed for mutations in seven genes associated with resistance to antituberculous four drugs: katG and inhA promoter for isoniazid (INH); rpoB for rifampicin (RIF); gyrA and gyrB for ofloxacin (OFLX); and rrs and eis promoter for kanamycin (KAN). All strains were genotyped by spoligotyping and 15-loci MIRU-VNTR analysis.

RESULTS

A total of 39 distinct mutations were found at the seven loci in 114/123 (92.7%) MDR-TB isolates. Frequencies of INH, RIF, OFLX and KAN resistance-associated mutations were 82.1% (101/123), 83.7% (103/123), 92.1% (35/38) and 76.2% (16/21), respectively. The most prevalent mutations involved in resistance were: Ser315Thr in katG (70/123; 56.9%) and C(-15)T in inhA (15/123; 12.2%) for INH; Ser531Leu in rpoB (72/123; 58.5%) for RIF; Asp94Gly in gyrA (10/38; 26.3%) for OFLX; and A1401G in rrs (12/21; 57.1%) for KAN. Four novel gyrB mutants (Leu442Leu, Ser447Phe, Asn499Thr and Ala504Val) were identified. Mutations in katG, rpoB (or both) and the inhA promoter showed a sensitivity of 75.6% and specificity of 97.0% for detection of MDR-TB. DNA sequencing of the seven loci was 57.1% sensitive and 91.0% specific for prediction of XDR-TB isolates.

CONCLUSION

These results may be of value in rapid molecular detection of MDR- and XDR-TB isolates in clinical samples in Hebei Province.