Prevalence and Molecular Characterization of Second-Line Drugs Resistance among Multidrug-Resistant<i>Mycobacterium tuberculosis</i>Isolates in Southwest of China

Abstract

This study aimed to investigate the prevalence of multidrug-resistant tuberculosis (MDR-TB) isolates resistant to the second-line antituberculosis drugs (SLDs) and its association with resistant-related gene mutations in <i>Mycobacterium tuberculosis</i> (<i>M.tb</i>) isolates from Southwest of China. There were 81 isolates resistant to at least one of the SLDs among 156 MDR-TB isolates (81/156, 51.9%). The rates of general resistance to each of the drugs were as follows: OFX (66/156, 42.3%), KAN (26/156, 16.7%), CAP (13/156, 8.3%), PTO (11/156, 7.1%), PAS (22/156, 14.1%), and AMK (20/156, 12.8%). Therefore, the most predominant pattern was resistant to OFX compared with other SLDs (<i>P</i> < 0.001). The results of sequencing showed that 80.2% OFX-resistant MDR-TB isolates contained <i>gyrA</i> mutation and 88.5% KAN-resistant isolates had <i>rrs</i> mutations with the most frequent mutation being A1401G. These results suggest that improper use of SLDs especially OFX is a real threat to effective MDR-TB treatment not only in China but also in the whole world. Furthermore the tuberculosis control agencies should carry out SLDs susceptibility testing and rapid screening in a broader population of TB patients immediately and the SLDs should be strictly regulated by the administration in order to maintain their efficacy to treat MDR-TB.