Department of Microbiology, Assam University, Silchar, Assam, India.
Department of Microbiology, Silchar Medical College and Hospital, Silchar, Assam, India.
J Glob Antimicrob Resist. 2017 Sep;10:40-46. doi: 10.1016/j.jgar.2017.03.010. Epub 2017 Jun 12.
Quinolone antimicrobials are frequently misused due to self-medication and suboptimal dose administration, leading to the development of resistance as well as treatment failure. The present study aimed to characterise plasmid-mediated quinolone resistance (PMQR) determinants and their genetic selection in the presence of quinolone stress within members of the Enterobacteriaceae.
A total of 209 non-duplicate Enterobacteriaceae isolates were collected from hospital and community health centres over the period July 2013-June 2014. Molecular characterisation of phenotypically screened quinolone-resistant isolates was done by multiplex PCR. Plasmids bearing the qnr and aac(6')-Ib-cr genes were transformed into Escherichia coli DH5α and were selected on Muller-Hinton agar plates containing 0.25μg/mL and 0.5μg/mL ciprofloxacin, norfloxacin, ofloxacin, levofloxacin and moxifloxacin. Conjugation experiments were performed to determine whether the aac(6')-Ib-cr- and qnr-carrying plasmids were self-transferable.
The transformation assay revealed that transformants carrying qnrA could be selected in media containing norfloxacin, ciprofloxacin and levofloxacin, whereas qnrB and aac(6')-Ib-cr were selected on media containing norfloxacin and ciprofloxacin. Transformed qnrD could be selected in media containing norfloxacin and ofloxacin, and qnrS was selected only in the presence of levofloxacin.
The presence of qnr genes has been associated with an increase in quinolone minimum inhibitory concentrations (MICs) and therefore leads to treatment failure when quinolones are used as selective therapeutic drugs. Since PMQR determinants have a high prevalence, effective measures should be taken and surveillance should be performed in order to avoid treatment failures using this group of antimicrobials.
由于自我用药和剂量使用不当，喹诺酮类抗菌药物经常被滥用，导致耐药性的产生和治疗失败。本研究旨在描述肠杆菌科成员在喹诺酮类药物压力下，质粒介导的喹诺酮类耐药（PMQR）决定因素及其遗传选择。
2013 年 7 月至 2014 年 6 月期间，从医院和社区卫生中心共收集了 209 株非重复的肠杆菌科分离株。通过多重 PCR 对表型筛选出的喹诺酮类耐药分离株进行分子特征分析。将携带 qnr 和 aac(6')-Ib-cr 基因的质粒转化到大肠杆菌 DH5α 中，并在含有 0.25μg/mL 和 0.5μg/mL 环丙沙星、诺氟沙星、氧氟沙星、左氧氟沙星和莫西沙星的 Muller-Hinton 琼脂平板上进行选择。进行接合实验以确定携带 aac(6')-Ib-cr 和 qnr 质粒是否具有自我转移能力。
转化试验表明，携带 qnrA 的转化子可以在含有诺氟沙星、环丙沙星和左氧氟沙星的培养基中被选择，而 qnrB 和 aac(6')-Ib-cr 则可以在含有诺氟沙星和环丙沙星的培养基中被选择。携带 qnrD 的转化子可以在含有诺氟沙星和氧氟沙星的培养基中被选择，而 qnrS 仅在左氧氟沙星存在时被选择。
qnr 基因的存在与喹诺酮类最低抑菌浓度（MICs）的增加有关，因此当喹诺酮类药物作为选择性治疗药物使用时，会导致治疗失败。由于 PMQR 决定因素的高流行率，应采取有效措施并进行监测，以避免使用这组抗生素治疗失败。
