Division of Animal Infectious Diseases, State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
Int J Antimicrob Agents. 2013 Jul;42(1):87-9. doi: 10.1016/j.ijantimicag.2013.03.011. Epub 2013 May 29.
There are many studies on fluoroquinolone (FQ) resistance in the literature, but little is known regarding the molecular characterisation of FQ-resistant Haemophilus parasuis. In this study, a total of 138 H. parasuis isolates were examined, among which 83 (60.1%) were resistant to enrofloxacin (EFX) and 8 (5.8%) were resistant to levofloxacin (LFX) as determined by Etest. Ten point mutations in the quinolone resistance-determining regions of gyrA, gyrB, parC and parE were detected by PCR and DNA sequencing. Interestingly, 100% of the resistant isolates contained mutations at 87D of gyrA, but other mutations occurred less frequently. Furthermore, it was found that there was synergy between 73S→R/I in parC and other point mutations with respect to FQ resistance. To examine the effect of different point mutations on FQ resistance, the minimum inhibitory concentrations of EFX and LFX were determined for strains generated by site-directed mutagenesis, and three point mutations (gyrA 87D→N, parC 73S→R and parE 551T→A) were shown to be involved in FQ resistance.
文献中有许多关于氟喹诺酮（FQ）耐药性的研究，但对于猪嗜血杆菌中 FQ 耐药性的分子特征知之甚少。在本研究中，共检测了 138 株 H. parasuis 分离株，其中 83 株（60.1%）对恩诺沙星（EFX）耐药，8 株（5.8%）对左氧氟沙星（LFX）耐药，这是通过 Etest 确定的。通过 PCR 和 DNA 测序检测到喹诺酮耐药决定区中 gyrA、gyrB、parC 和 parE 的 10 个点突变。有趣的是，100%的耐药分离株在 gyrA 的 87D 处都含有突变，但其他突变发生的频率较低。此外，还发现 parC 中的 73S→R/I 与其他点突变与 FQ 耐药性之间存在协同作用。为了研究不同点突变对 FQ 耐药性的影响，通过定点诱变生成的菌株确定了 EFX 和 LFX 的最小抑菌浓度，结果显示三个点突变（gyrA 87D→N、parC 73S→R 和 parE 551T→A）与 FQ 耐药性有关。
