摘要
目标
弗氏柠檬酸杆菌是一种重要的机会性病原体，耐碳青霉烯类菌株对公众健康构成了重大挑战。本文通过全基因组测序，报道了一株来自医院污水的碳青霉烯类耐药弗氏梭菌SCLZS47的抗菌基因的遗传特征。
方法
采用肉汤微量稀释法测定抗菌药物的敏感性。SCLZS47的全基因组序列是通过使用HiSeq 2000和PacBio-RSII平台获得的。分别使用PlasmidFinder、ResFinder和ISfinder鉴定质粒不相容性类型、抗性基因和插入元件。
后果
SCLZS47有一个环状染色体和三个抗性质粒，它携带23个已知的ARG。其中，blaCMY-135和三个拷贝的blaCTX-M-14位于染色体上。16个ARG聚集在多药耐药性（MDR）质粒的两个附属模块中，同源重组和转座事件有助于这些MDR区域的形成。碳青霉烯酶基因blaKPC-2和blaNDM-1分别由pCKPC18-1样质粒和pNDM-HN380样质粒携带。结合实验表明，KPC-2-和NDM-1-编码质粒都是可传播的。
结论
分析抗性基因的遗传特征将有助于更好地了解其在细菌群落中的传播机制和动力学，这具有重要的临床意义。
ABSTRACT
Objectives
Citrobacter freundii is an important opportunistic pathogen, and carbapenem-resistant strains pose a significant challenge to public health. Here we report the genetic features of antimicrobial resistance genes of a carbapenem-resistant C. freundii SCLZS47 from hospital sewage by using whole genome sequencing.

Methods
Antimicrobial susceptibility was determined by the broth microdilution method. Whole genomic sequences of SCLZS47 were obtained by using the HiSeq 2000 combined with PacBio RSII platforms. Plasmid incompatibility types, resistance genes, and insertion elements were identified using the PlasmidFinder, ResFinder, and ISfinder, respectively.

Results
SCLZS47 has a circular chromosome and three resistance plasmids, and it carries 23 known ARGs. Among them, blaCMY-135 and three copies of blaCTX-M-14 are located on the chromosome. Sixteen ARGs are clustered in two accessory modules of a multidrug resistance (MDR) plasmid, and homologous recombination and transposition events contribute to the formation of these MDR regions. Carbapenemase genes blaKPC-2 and blaNDM-1 are carried by a pCKPC18-1-like plasmid and a pNDM-HN380-like plasmid, respectively. Conjugation experiments indicated that both KPC-2- and NDM-1-encoding plasmids are transmissible.

Conclusion
Analysis of the genetic features of resistance genes would help to better understand their transmission mechanisms and dynamics in bacterial community, which has significant clinical implications.

https://www.sciencedirect.com/science/article/pii/S2213716522000947