Increased prevalence of levofloxacin-resistant Mycobacterium tuberculosis in China is associated with specific mutations within the gyrA gene

Abstract Objectives To compare the prevalence of levofloxacin (LFX) resistance and the population structure of Mycobacterium tuberculosis (MTB) with different mutations conferring LFX resistance between 2005 and 2015. Methods 542 MTB isolates were randomly selected from pulmonary TB patients in 2005 and 2015 were analysed for minimum inhibitory concentrations (MICs) and quinolone resistance-determining regions (QRDR) respectively. Results A total of 542 MTB isolates were analyzed, of which 111 (20.5%) were resistant to LFX. Of 42 and 69 LFX-resistant isolates from 2005 and 2015 respectively, 40.6% (28/69) had MIC high-level LFX resistance in 2015, which was significantly higher than 16.7% (7/42) in 2005 (P = 0.02). There are 87 (78.4%) mutations of these 111 LFX-resistant isolates. In addition, a significant difference in proportion was observed in the isolates with mutations in codon 90 of the gyrA gene between 2005 and 2015 (11.9% in 2005 versus 29.0% in 2015, P = 0.04). Conclusion The prevalence of LFX-resistant TB in China was an alarming increase between 2005 and 2015. This dynamic change is majorly attributed to the increase of high-level LFX-resistance. Moreover, a significant difference was noted in the proportion of LFX-resistant isolates harboring specific mutations within the gyrA gene between 2005 and 2015.