Abstract：Objective To learn the characteristics of second-line drug resistance and related gene mutations of multidrug-resistant Mycobacterium tuberculosis ( MDR-TB ) Beijing genotype strains. Methods The MDR-TB isolates in Hwa Mei Hospital from 2017 to 2019 were enrolled and detected using RD105 deletion-targeted multiplex polymerase chain reaction (PCR). The proportion method for drug susceptibility test was used to detect the drug-resistant profiles against kanamycin, amikacin, capreomycin, ofloxacin and levofloxacin. The gene sequencing of rrs, tlyA, eis, gidB, gyrA and gyrB was conducted by PCR compared with H37RV strain. The differences in the rates of drug resistance and mutation between Beijing and non-Beijing genotype strains were examined to understand the characteristics of Beijing genotype strains. Results There were 106 Beijing genotype and 27 non-Beijing genotype strains in 133 MDR-TB isolates. The drug resistance rates of kanamycin, amikacin, capreomycin, ofloxacin and levofloxacin in Beijing genotype strains were 9.43%, 7.55%, 3.77%, 32.08% and 32.08%, respectively. The rates of quasi-extensive and extensive drug resistance in Beijing genotype strains were 30.19% and 7.55%. The gene mutation rates of rrs, tlyA, eis, gidB, gyrA and gyrB in Beijing genotype strains were 7.55%, 7.55%, 1.89%, 2.83%, 36.79% and 2.83%, respectively. There were no significantly differences between Beijing and Non-Beijing genotype strains in the factors above ( P>0.05 ). The gene rrs, tlyA, eis, gidB, gyrA and gyrB had 2, 1, 2, 2, 5 and 3 mutation types, respectively, with single base substitution as the main type. Conclusion Beijing genotype strains are dominant in MDR-TB, with high resistance to fluoroquinolones and mainly gyrA gene mutation.
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