Servicio Antimicrobianos, National Reference Laboratory in Antimicrobial Resistance (NRLAR), National Institute of Infectious Diseases (INEI), ANLIS "Dr. Carlos G. Malbrán", Buenos Aires City, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires City, Argentina.
PLoS One. 2024 Feb 26;19(2):e0294820. doi: 10.1371/journal.pone.0294820. eCollection 2024.
Mobile colistin resistance (mcr) genes were described recently in Gram-negative bacteria including carbapenem-resistant Enterobacterales. There are ten mcr genes described in different Gram-negative bacteria, however, Escherichia coli harboring mcr-1 gene is by far the most frequent combination. In Argentina, mcr-1 gene was characterized only on plasmids belonging to IncI2 group. The aim of this work was to get new insights of mcr-1-harboring plasmids from E. coli. Eight E. coli isolates from a larger collection of 192 clinical E. coli isolates carrying the mcr-1 gene were sequenced using next generation technologies. Three isolates belonged to ST131 high-risk clone, and five to single ST, ST38, ST46, ST226, ST224, and ST405. Eight diverse mcr-1-harboring plasmids were analyzed: IncI2 (1), IncX4 (3), IncHI2/2A (3) and a hybrid IncFIA/HI1A/HI1B (1) plasmid. Plasmids belonging to the IncI2 (n = 1) and IncX4 (n = 3) groups showed high similarity with previously described plasmids. Two IncHI2/HI2A plasmids, showed high identity between them, while the third, showed several differences including additional resistance genes like tet(A) and floR. One IncFIA/H1A/H1B hybrid plasmid was characterized, highly similar to pSRC27-H, a prototype plasmid lacking mcr genes. mcr-1.5 variant was found in four plasmids with three different Inc groups: IncI2, IncHI2/HI2A and the hybrid FIA/HI1A/HI1B plasmid. mcr-1.5 variant is almost exclusively described in our country and with a high frequency. In addition, six E. coli isolates carried three allelic variants codifying for CTX-M-type extended-spectrum-β-lactamases: blaCTX-M-2 (3), blaCTX-M-65 (2), and blaCTX-M-14 (1). It is the first description of mcr-1 harboring plasmids different to IncI2 group in our country. These results represents new insights about mcr-1 harboring plasmids recovered from E. coli human samples from Argentina, showing different plasmid backbones and resistance gene combinations.
最近在包括耐碳青霉烯肠杆菌科在内的革兰氏阴性菌中描述了移动性多粘菌素耐药（mcr）基因。在不同的革兰氏阴性菌中已描述了十个 mcr 基因，但迄今为止，携带 mcr-1 基因的大肠杆菌是最常见的组合。在阿根廷，mcr-1 基因仅在属于 IncI2 组的质粒上进行了特征描述。本研究的目的是从大肠杆菌中获得对 mcr-1 基因具有抗性的质粒的新见解。从更大的 192 株携带 mcr-1 基因的临床大肠杆菌分离株中，使用下一代技术对 8 株大肠杆菌分离株进行了测序。其中 3 株属于高风险克隆 ST131，5 株属于单 ST，ST38、ST46、ST226、ST224 和 ST405。分析了 8 种不同的 mcr-1 基因携带质粒：IncI2（1）、IncX4（3）、IncHI2/2A（3）和混合 IncFIA/HI1A/HI1B（1）质粒。属于 IncI2（n = 1）和 IncX4（n = 3）组的质粒与以前描述的质粒高度相似。两个 IncHI2/HI2A 质粒之间具有高度相似性，而第三个质粒则存在许多差异，包括额外的耐药基因，如 tet(A)和 floR。一个 IncFIA/H1A/H1B 混合质粒被鉴定，与缺乏 mcr 基因的原型质粒 pSRC27-H 高度相似。在具有三个不同 Inc 组的四个质粒中发现了 mcr-1.5 变体：IncI2、IncHI2/HI2A 和混合的 FIA/HI1A/HI1B 质粒。mcr-1.5 变体几乎仅在我国描述，且频率较高。此外，6 株大肠杆菌分离株携带三种编码 CTX-M 型超广谱β-内酰胺酶的等位基因变体：blaCTX-M-2（3）、blaCTX-M-65（2）和 blaCTX-M-14（1）。这是首次在我国描述的不属于 IncI2 组的 mcr-1 基因携带质粒。这些结果代表了从阿根廷人类大肠杆菌样本中获得的 mcr-1 基因携带质粒的新见解，这些质粒具有不同的质粒骨架和耐药基因组合。
