School of Medicine, Hangzhou Normal University, Hangzhou, 310036, Zhejiang, China.
Department of Primary Health Care, Health and Family Planning Commission of Zhejiang Province, Hangzhou, 310006, Zhejiang, China.
World J Microbiol Biotechnol. 2018 May 18;34(6):72. doi: 10.1007/s11274-018-2454-3.
The aim of this study was to explore the fluoroquinolone resistance mechanism of aac (6')-Ib-cr and qnrS gene by comparing complete sequences and stability of the aac(6')-Ib-cr- and qnrS-positive plasmids from Shigella isolates in the Hangzhou area of China. The complete sequences of four newly acquired plasmids carrying aac(6')-Ib-cr or qnrS were compared with those of two plasmids obtained previously and two similar reference Escherichia coli plasmids. The results showed that the length, antibiotic resistance genes and genetic environment were different among the plasmids. Moreover, the plasmid stability of three wild-type isolates and five plasmid transformants carrying aac(6')-Ib-cr and/or qnrS was measured in vitro, and all eight isolates were found to have lost their aac(6')-Ib-cr- or qnrS-positive plasmids to a different extent at different stages. When the plasmids were electroporated into Shigella flexneri or they lost positive plasmids, the MICs of ciprofloxacin increased or decreased two- to eightfold for aac(6')-Ib-cr-positive plasmids and 16- to 32-fold for qnrS-positive plasmids. To our knowledge, this is the first report comparing the complete sequences and describing stability for the aac(6')-Ib-cr- and qnrS-positive plasmids from Shigella isolates.
本研究旨在通过比较中国杭州地区志贺菌分离株中携带 aac(6')-Ib-cr 和 qnrS 基因的完整质粒序列及其稳定性，探讨氟喹诺酮耐药机制。对 4 个新获得的携带 aac(6')-Ib-cr 或 qnrS 的质粒的完整序列与先前获得的 2 个质粒和 2 个相似的参考大肠杆菌质粒进行了比较。结果表明，质粒的长度、抗生素耐药基因和遗传环境存在差异。此外，还测量了 3 个野生型分离株和 5 个携带 aac(6')-Ib-cr 和/或 qnrS 的质粒转化子的质粒稳定性，所有 8 个分离株在不同阶段均不同程度地丢失了其 aac(6')-Ib-cr-或 qnrS 阳性质粒。当质粒电穿孔到福氏志贺菌中或它们丢失阳性质粒时，aac(6')-Ib-cr 阳性质粒的环丙沙星 MIC 值增加或减少了 2 至 8 倍，qnrS 阳性质粒的 MIC 值增加了 16 至 32 倍。据我们所知，这是首次比较志贺菌分离株中携带 aac(6')-Ib-cr 和 qnrS 基因的完整质粒序列及其稳定性的报道。
