Fluoroquinolone resistance in multidrug-resistantMycobacterium tuberculosisindependent of fluoroquinolone use

During the 1990s, multidrug-resistant tuberculosis (MDR-TB), resistant to at least isoniazid and rifampin, emerged as a great threat to global tuberculosis (TB) control [1]. For most MDR-TB patients, the World Health Organization (WHO) recommends a treatment regimen including second-line anti-TB drugs [2]. One of the most effective second-line drugs is fluoroquinolone [3]. During the treatment, MDR-TB may develop resistance to fluoroquinolone, or even become extensively drug-resistant (XDR-TB), which is resistant to both fluoroquinolone and at least one of three injectable second-line drugs [4]. The main genetic mechanism of fluoroquinolone resistance lies in the mutations in the quinolone-resistance-determining region of gyrA and gyrB [5]. Fluoroquinolone resistance in multidrug-resistant tuberculosis develops with various anti-tuberculosis regimens