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

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: A total 542 MTB isolates were randomly selected from pulmonary tuberculosis (TB) patients in 2005 and 2015 and analyzed regarding minimum inhibitory concentrations (MICs) and quinolone resistance-determining regions (QRDR). Results: One hundred and eleven of the 542 MTB isolates analyzed (20.5%) were resistant to LFX. There were 42 and 69 LFX-resistant isolates from 2005 and 2015, respectively, and MIC high-level LFX resistance was significantly higher in 2015 (40.6%, 28/69) than in 2005 (16.7%, 7/42) (p = 0.02). There were 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). Conclusions: There was an alarming increase in prevalence of LFX-resistant TB in China between 2005 and 2015. This dynamic change is mostly attributed to the increase in 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. Keywords: Tuberculosis, Levofloxacin, Drug resistance, gyrA, China