Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan.
Department of Energy, Joint Genome Institute, Walnut Creek, CA, USA.
J Microbiol Immunol Infect. 2021 Aug;54(4):658-664. doi: 10.1016/j.jmii.2020.04.019. Epub 2020 May 23.
Shewanella algae is a zoonotic pathogen that poses a serious health threat to immunocompromised hosts. Treatment of S. algae infections is challenging due to the pathogen's intrinsic resistance to a variety of β-lactam antibiotics. Therapeutic options have become further limited by the emergence of quinolone-resistant strains. Currently, there are few studies concerning the genetic and molecular mechanisms underlying acquired quinolones resistance in S. algae. qnrA was once proposed as the candidate gene related to quinolones resistance in S. algae. However, recent studies demonstrated qnrA are highly conservative and does not confer resistance to quinolones in S. algae.
A total of 27 non-duplicated isolates of S. algae strains were examined. MICs of ciprofloxacin were determined using Vitek 2. Whole genome sequencing was performed using MiSeq platform. Comprehensive Antibiotic Resistance Database and ResFinder were used for annotation of quinolones resistance genes. Multiple sequence alignment by EMBOSS Clustal Omega were used to identified mutation in quinolone resistance-determining regions. To investigation of the alteration of protein structure induced by mutation, in silico molecular docking studies was conducted using Accryl Discovery studio visualizer.
All S. algae harbored the quinolone-resistance associated genes (qnrA, gyrA, gyrB, parC, and parE) regardless its resistance to ciprofloxacin. Comparison of these genomes identified a nonsynonymous mutation (S83V) in chromosome-encoded gyrase subunits (GyrA) in quinolone-resistant strain. We found this mutation disrupts the water-metal ion bridge, reduces the affinity of the quinolone-enzyme complex for the metal ions and therefore decrease the capability of quinolones to stabilize cleavage complexes.
The study provides insight into the quinolone resistance mechanisms in S. algae, which would be helpful for the evolution of antibiotic resistance in this bacterium.
海栖假单胞菌是一种人畜共患病病原体，对免疫功能低下的宿主构成严重的健康威胁。由于该病原体对多种β-内酰胺类抗生素具有固有耐药性，因此治疗海栖假单胞菌感染具有挑战性。治疗选择因喹诺酮耐药株的出现而进一步受到限制。目前，关于海栖假单胞菌获得性喹诺酮耐药的遗传和分子机制的研究很少。qnrA 曾被提议为与海栖假单胞菌喹诺酮耐药相关的候选基因。然而，最近的研究表明 qnrA 高度保守，并且不会赋予海栖假单胞菌对喹诺酮的耐药性。
共检测了 27 株非重复的海栖假单胞菌菌株。使用 Vitek 2 测定环丙沙星的 MIC。使用 MiSeq 平台进行全基因组测序。使用综合抗生素耐药数据库和 ResFinder 注释喹诺酮耐药基因。使用 EMBOSS Clustal Omega 进行多重序列比对，以鉴定喹诺酮耐药决定区的突变。为了研究突变引起的蛋白质结构的改变，使用 Accryl Discovery studio visualizer 进行了计算机分子对接研究。
所有海栖假单胞菌均携带喹诺酮耐药相关基因（qnrA、gyrA、gyrB、parC 和 parE），无论其对环丙沙星的耐药性如何。比较这些基因组发现，喹诺酮耐药株染色体编码的回旋酶亚基（GyrA）中存在非同义突变（S83V）。我们发现这种突变破坏了水-金属离子桥，降低了喹诺酮-酶复合物与金属离子的亲和力，从而降低了喹诺酮稳定裂解复合物的能力。
该研究深入了解了海栖假单胞菌的喹诺酮耐药机制，这将有助于该细菌抗生素耐药性的演变。
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