Zhang Xuefei, Wang Leilei, Li Dan, Wang Chen, Guo Qinglan, Wang Minggui
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
Key Laboratory of Clinical Pharmacology of Antibiotics, National Heath Commission of the People's Republic of China, Shanghai, China.
J Antimicrob Chemother. 2021 Dec 24;77(1):83-88. doi: 10.1093/jac/dkab342.
To characterize the novel subclass B1 MBL AFM-1, encoded by a blaIMP-45-bearing megaplasmid from a carbapenem-resistant Pseudomonas aeruginosa (CRPA) clinical isolate.
CRPA HS17-127 and its transconjugant were discovered to carry blaAFM-1 in our previous study. blaAFM-1 and blaNDM-1 were cloned and expressed in Escherichia coli TOP10 and P. aeruginosa PAO1, respectively, to test the resistance phenotype. Kinetic studies were performed to elucidate the biochemical characteristics of the AFM-1 enzyme. Comparative genomic analysis was applied to investigate the genetic context of blaAFM-1.
PAO1 transconjugant TcHS17-127 exhibited carbapenem resistance with an imipenem MIC of 64 mg/L. E. coli transformants with cloned blaAFM-1 or blaNDM-1 had increased MICs of all β-lactams tested (except aztreonam) and imipenem MICs of 4-8 mg/L. Kinetic studies showed that AFM-1 had greater catalytic efficiency against cephalosporins than carbapenems. blaAFM-1 was located on a 486 963 bp IncP-2 plasmid, pHS17-127, containing a 57.3 kb MDR Tn1403-derivative transposon, Tn6485e, which is genetically closest to the blaIMP-45-bearing Tn6485 transposon but has acquired an extra ISCR27n3-blaAFM-1 module. Multicentre surveillance of 605 P. aeruginosa clinical isolates identified three blaAFM carriers from different STs. Two of them co-carried blaAFM-1 and blaIMP-45. A BLAST search against the NCBI database showed six blaAFM carriers on various plasmids and the chromosomes of different Gram-negative species.
The blaAFM-1 gene confers carbapenem resistance and has been captured in distinct species of non-fermenters. Co-carriage of blaAFM-1 and blaIMP-45 in an MDR transposon on a conjugative plasmid can be expected to promote further dissemination of blaMBLs.
对一种新型B1亚类MBL AFM-1进行特性分析，该基因由一株耐碳青霉烯类铜绿假单胞菌（CRPA）临床分离株携带blaIMP-45的大质粒编码。
在我们之前的研究中发现CRPA HS17-127及其接合子携带blaAFM-1。分别将blaAFM-1和blaNDM-1克隆并在大肠杆菌TOP10和铜绿假单胞菌PAO1中表达，以测试耐药表型。进行动力学研究以阐明AFM-1酶的生化特性。应用比较基因组分析来研究blaAFM-1的遗传背景。
PAO1接合子TcHS17-127表现出对碳青霉烯类的耐药性，亚胺培南MIC为64mg/L。携带克隆的blaAFM-1或blaNDM-1的大肠杆菌转化子对所有测试的β-内酰胺类药物（除氨曲南外）的MIC增加，亚胺培南MIC为4-8mg/L。动力学研究表明，AFM-1对头孢菌素的催化效率高于碳青霉烯类。blaAFM-1位于一个486963bp的IncP-2质粒pHS17-127上，该质粒含有一个57.3kb的多药耐药Tn1403衍生转座子Tn6485e，它在遗传上与携带blaIMP-45的Tn6485转座子最接近，但获得了一个额外的ISCR27n3-blaAFM-1模块。对605株铜绿假单胞菌临床分离株的多中心监测发现了来自不同ST型的3个blaAFM携带者。其中两个同时携带blaAFM-1和blaIMP-45。在NCBI数据库中进行的BLAST搜索显示，在不同革兰氏阴性菌的各种质粒和染色体上有6个blaAFM携带者。
blaAFM-1基因赋予碳青霉烯类耐药性，并已在不同种类的非发酵菌中被捕获。预计在接合性质粒上的多药耐药转座子中共同携带blaAFM-1和blaIMP-45会促进blaMBLs的进一步传播。
