Department of Clinical Microbiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
Department of Clinical Laboratory Science The International Peace Maternity & Child Health Hospital of China Welfare Institute (IPMCH), Shanghai, China.
Antimicrob Resist Infect Control. 2020 Apr 15;9(1):52. doi: 10.1186/s13756-020-00711-y.
Quinolones are commonly used for treatment of infections by bacteria of the Enterobacteriaceae family. However, the rising resistance to quinolones worldwide poses a major clinical and public health risk. This study aimed to characterise a novel multiple resistance plasmid carrying three plasmid-mediated quinolone resistance genes in Escherichia coli clinical stain RJ749.
MICs of ceftriaxone, cefepime, ceftazidime, ciprofloxacin, and levofloxacin for RJ749 and transconjugant c749 were determined by the Etest method. Conjugation was performed using sodium azide-resistant E. coli J53 strain as a recipient. The quinolone resistance-determining regions of gyrA, gyrB, parC, and parE were PCR-amplified.
RJ749 was highly resistant to quinolones, while c749 showed low-level resistance. S1-nuclease pulsed-field gel electrophoresis revealed that RJ749 and c749 both harboured a plasmid. PCR presented chromosomal mutation sites of the quinolone resistance-determining region, which mediated quinolone resistance. The c749 genome comprised a single plasmid, pRJ749, with a multiple resistance region, including three plasmid-mediated quinolone resistance (PMQR) genes (aac (6')-Ib-cr, qnrS2, and oqxAB) and ten acquired resistance genes. One of the genes, qnrS2, was shown for the first time to be flanked by two IS26s. Three IS26-mediated circular molecules carrying the PMQR genes were detected.
We revealed the coexistence of three PMQR genes on a multiple resistance plasmid and a new surrounding genetic structure of qnrS2 flanked by IS26 elements. IS26 plays an important role in horizontal spread of quinolone resistance.
喹诺酮类药物常用于治疗肠杆菌科细菌感染。然而，全球范围内喹诺酮类药物的耐药性不断上升，对临床和公共卫生构成了重大威胁。本研究旨在对携带三种质粒介导的喹诺酮耐药基因的大肠杆菌临床株 RJ749 中的新型多重耐药质粒进行特征描述。
采用 Etest 法测定 RJ749 和转接合子 c749 对头孢曲松、头孢吡肟、头孢他啶、环丙沙星和左氧氟沙星的 MIC 值。采用耐叠氮化钠的大肠杆菌 J53 菌株作为受体进行接合。PCR 扩增 gyrA、gyrB、parC 和 parE 的喹诺酮耐药决定区。
RJ749 对喹诺酮类药物高度耐药，而 c749 表现出低水平耐药。S1-核酸酶脉冲场凝胶电泳显示 RJ749 和 c749 均携带质粒。PCR 显示了喹诺酮耐药决定区的染色体突变位点，这些突变介导了喹诺酮耐药。c749 基因组包含一个单一的质粒 pRJ749，该质粒带有一个多重耐药区，包括三个质粒介导的喹诺酮耐药（PMQR）基因（aac（6'）-Ib-cr、qnrS2 和 oqxAB）和十个获得性耐药基因。其中一个基因 qnrS2 首次被发现位于两个 IS26 之间。检测到三个携带 PMQR 基因的 IS26 介导的环形分子。
我们揭示了三种 PMQR 基因共存于一个多重耐药质粒上，以及 qnrS2 侧翼被 IS26 元件包围的新的周围遗传结构。IS26 在喹诺酮耐药的水平传播中发挥了重要作用。
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