Genotyping and drug susceptibility of Mycobacterium tuberculosis isolated in Changping district in Beijing, 2011-2015

Abstract

Objective: To understand the genotype distribution of Mycobacterium tuberculosis and the drug susceptibility of M. tuberculosis with different genotypes in Changping district of Beijing and evaluate the application of genotyping of M. tuberculosis in local tuberculosis (TB) prevention and control. Methods: A total of 1 099 M. tuberculosis strains isolated in Changping from 2011 to 2015 were used. Spoligotyping and 12-locus VNTR recommended by Gao were used for the genotyping of these isolates. In addition, the susceptibility of the M. tuberculosis isolates to rifampin (RFP), isoniazid (INH), ethambutol (EMB), streptomycin (SM), amikacin (AMK) and ofloxcin (OFX) were detected by using conventional drug susceptibility test. Results: From 2011 to 2015, the detection rate of OFX-resistance increased from 2.9% to 8.9% (P=0.01). Of all the M. tuberculosis isolates, 976 belonged to Beijing genotype (88.8%), and the other 123 belonged to non-Beijing genotype (11.2%). In addition, there were 189 ancient Beijing genotype isolates and 787 modern Beijing genotype isolates, respectively. The proportion of Beijing genotype strains showed no significant increase in the past five years (81.1% in 2011 vs. 82.0% in 2015). On the basis of VTNR genotyping, only 2 isolates belonged to one cluster (0.1%). In addition, the AMK resistant rate of Beijing genotype strains (1.7%) was significantly lower than that of non-Beijing genotype strains (4.9%, P=0.02). Compared with modern Beijing genotype strains, the SM resistant rate of ancient Beijing genotype strains was significantly higher (28.0% vs. 15.7%, P=0.01). Conclusions: In the past five years, the OFX- resistant rate of M.tuberculosis in Changping was in increase. There was no significant difference in the detection of Beijing genotype strains during this period. In addition, the low clustering rate indicated that the TB transmission rate was low in Changping.