Genetic characterisation of drug-resistant Mycobacterium tuberculosis in rural China: a population-based study

A population-based study was performed to characterise the genotype and phenotype of drug-resistant tuberculosis (TB) in the year 2004-2005 in two Chinese rural counties with different durations of DOTS implementation, Deqing and Guanyun.

Mycobacterium tuberculosis strains were isolated from respectively 164 and 187 patients registered at local TB dispensaries of Deqing and Guanyun. Drug susceptibility profiling and DNA sequencing were performed on the isolates.

A total of 223 isolates from 223 patients were identified as resistant to first-line drugs, of which 53 were multidrug-resistant TB (MDR-TB, i.e., resistant to isoniazid [INH] and rifampicin [RMP]). Mutations in katG were identified in 81 of 131 INH-resistant isolates (61.8%), all of which harboured the mutation in codon 315. Mutations related to RMP resistance occurred mostly in codon 531, 526 and 516 of the rpoB gene. Seventy-eight of the 115 streptomycin-resistant isolates carried a mutation in the rpsL gene at codon 43 or 88. A mutation in codon 306 of embB occurred in 21 ethambutol (EMB) resistant and 19 EMB-susceptible isolates.

Our data indicated that DNA sequencing of specific codons of the rpoB gene should be effective for predicting RMP resistance and MDR-TB in rural China.