Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.
Jinan Microecological Biomedicine Shandong Laboratory, Jinan, China.
Microbiol Spectr. 2024 Sep 3;12(9):e0049624. doi: 10.1128/spectrum.00496-24. Epub 2024 Jul 23.
Omadacycline and eravacycline are gradually being used as new tetracycline antibiotics for the clinical treatment of Gram-negative pathogens. Affected by various tetracycline-inactivating enzymes, there have been reports of resistance to eravacycline and omadacycline in recent years. We isolated a strain carrying the mobile tigecycline resistance gene (X4) from the feces of a patient in Zhejiang Province, China. The strain belongs to the rare ST485 sequence type. The isolate was identified as by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The MICs of antimicrobial agents were determined using either the agar dilution method or the micro broth dilution method. The result showed that the isolate was resistant to eravacycline (MIC = 32 mg/L), omadacycline (MIC > 64 mg/L), and tigecycline (MIC > 32 mg/L). Whole-genome sequencing revealed that the (X4) resistance gene is located on the IncFII(pCRY) conjugative plasmid. (X4) is flanked by IS, and we hypothesize that this association contributes to the spread of the resistance gene. Plasmids were analyzed by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, and electrotransformation experiment. We successfully transferred the plasmid carrying (X4) to the recipient bacteria by electrotransformation experiment. Compared with the DH-5α, the MICs of the transformant L3995-DH5α were increased by eight-fold for eravacycline and two-fold higher for omadacycline. Overall, the emergence of plasmid-borne (X4) resistance gene in a clinical isolate of ST485 underscores the essential requirement for the ongoing monitoring of (X4) to prevent and control its further dissemination in China.IMPORTANCEThere are still limited reports on strains harboring tetracycline-resistant genes in China, and L3995hy adds a new example to those positive for the (X4) gene. Importantly, our study raises concerns that plasmid-mediated resistance to omadacycline and eravacycline may spread further to a variety of ecological and clinical pathogens, limiting the choice of medication for extensively drug-resistant bacterial infections. Therefore, it is important to continue to monitor the prevalence and spread of (X4) and other tetracyclines resistance genes in and diverse bacterial populations.
奥马环素和依拉环素逐渐被用作治疗革兰氏阴性病原体的新型四环素抗生素。受各种四环素失活酶的影响，近年来已有依拉环素和奥马环素耐药的报道。我们从中国浙江省一位患者的粪便中分离出一株携带可移动替加环素耐药基因（X4）的菌株。该菌株属于罕见的 ST485 序列型。通过基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）鉴定该分离株为 。采用琼脂稀释法或微量肉汤稀释法测定抗菌药物的 MIC。结果表明，该分离株对依拉环素（MIC=32mg/L）、奥马环素（MIC>64mg/L）和替加环素（MIC>32mg/L）耐药。全基因组测序显示，（X4）耐药基因位于 IncFII(pCRY) 接合质粒上。（X4）位于 IS 侧翼，我们假设这种关联有助于耐药基因的传播。通过 S1-核酸酶脉冲场凝胶电泳（S1-PFGE）、Southern 印迹和电转化实验分析质粒。我们通过电转化实验成功地将携带（X4）的质粒转移到受体菌中。与 DH-5α 相比，转化子 L3995-DH5α 对依拉环素的 MIC 值增加了 8 倍，对奥马环素的 MIC 值增加了 2 倍。总体而言，临床分离株 ST485 中携带质粒介导的（X4）耐药基因的出现，凸显了持续监测（X4）以防止和控制其在中国进一步传播的必要性。
重要性：在中国，携带四环素耐药基因的 菌株报告仍然有限，而 L3995hy 为 基因阳性菌株增加了一个新的例子。重要的是，我们的研究表明，对奥马环素和依拉环素的质粒介导耐药性可能会进一步传播到各种生态和临床病原体，从而限制了对广泛耐药菌感染的药物选择。因此，继续监测 和不同细菌种群中（X4）和其他四环素耐药基因的流行和传播非常重要。
