摘要
目标
革兰氏阴性菌中移动替加环素灭活酶基因tet（X）介导的替加环蛋白耐药性是全球公共卫生的一个新问题。然而，关于tet（X）在自然环境中的分布信息有限。在这项研究中，我们调查了环境革兰氏阴性菌中tet（X）的存在。
方法
2021年3月，从越南河内的一个城市排水沟中获得了一种耐碳青霉烯和替加环素的夏门谢瓦内拉分离株（NUITM-VS1）。通过长读和短读测序进行全基因组测序分析，得出完整的基因组序列。基因组中的抗微生物耐药性基因（ARG）是基于定制的ARG数据库检测的，包括所有已知的替加环素耐药性基因。
后果
厦门谢瓦尼拉分离株NUITM-VS1在染色体上携带tet（X4）基因和blaOXA-48碳青霉烯酶基因。tet（X4）两侧是IS91家族转座酶基因，这表明tet（X4）的获得是由这种可移动基因元件（MGE）介导的，而在blaOXA-48周围没有发现MGE，这与先前的研究结果一致，即blaOXA48-样β-内酰胺酶基因是谢瓦内拉属中物种特异性的内在ARG。
结论
据我们所知，这是首次报道一种携带tet（X4）的Shewanella sp.分离物。我们的研究结果为水环境中细菌中具有临床意义的ARGs动力学的复杂性提供了遗传学证据。
ABSTRACT
Objectives
Tigecycline resistance mediated by the mobile tigecycline-inactivating enzyme gene tet(X) in Gram-negative bacteria is an emerging concern for global public health. However, limited information is available on the distribution of tet(X) in the natural environment. In this study, we investigated the presence of tet(X) in environmental Gram-negative bacteria.

Methods
A carbapenem- and tigecycline-resistant Shewanella xiamenensis isolate (NUITM-VS1) was obtained from an urban drainage in Hanoi, Vietnam, in March 2021. Whole-genome sequencing analysis was performed by long- and short-read sequencing, resulting in a complete genome sequence. Antimicrobial resistance genes (ARGs) in the genome were detected based on the custom ARG database, including all known tigecycline resistance genes.

Results
Shewanella xiamenensis isolate NUITM-VS1 harboured the tet(X4) gene and the blaOXA-48 carbapenemase gene on the chromosome. tet(X4) was flanked by IS91 family transposase genes, suggesting that the acquisition of tet(X4) was mediated by this mobile gene element (MGE), whereas no MGE was found surrounding blaOXA-48, consistent with previous findings that blaOXA-48-like β-lactamase genes are species-specific intrinsic ARGs in Shewanella spp.

Conclusion
To the best of our knowledge, this is the first report of a tet(X4)-harbouring Shewanella sp. isolate. Our results provide genetic evidence of the complexity of the dynamics of clinically important ARGs among bacteria in the water environment.

https://www.sciencedirect.com/science/article/pii/S2213716522000042