Sequencing analysis of the quinolone resistance-determining region (QRDR)

In order to detect mutations within the QRDR in 2 subunits of both DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE), polymerase chain reaction (PCR) and sequencing analysis were performed using the specific primer pairs summarized in Table 2. Briefly, after amplification of the QRDR by PCR, the PCR products were cloned into pCR 2.1-TOPO vectors (Invitrogen, USA) and introduced into Escherichia coli DH5α cells. Sequencing analysis of the QRDR from purified plasmids of competent cells was performed by using ABI PRISM BigDye Terminator v3.1 Cycle Sequencing Kits (Applied Biosystems, USA).

QRDR, quinolone resistance-determining region.