Yang Chen, Chen Kaichao, Chan Edward Wai-Chi, Yao Wen, Chen Sheng
College of Animal Science & Technology, Nanjing Agricultural University, Nanjing, China.
Shenzhen Key Lab for Food Biological Safety Control, Food Safety and Technology Research Center, Hong Kong PolyU Shenzhen Research Institute, Shenzhen, China.
Front Microbiol. 2020 Sep 18;11:556227. doi: 10.3389/fmicb.2020.556227. eCollection 2020.
Resistance to ciprofloxacin, a treatment choice for infections, has increased dramatically in recent years in particular in serotype Derby with most of strains carrying chromosome-encoded multiple plasmid-mediated quinolone resistance (PMQR) genes. In this work, we discovered a conjugative plasmid, pSa64-96kb, in a Derby isolate, namely Sa64, which could extract and fuse to a multiple drug resistance (MDR) DNA fragment containing two PMQR genes, , and located on the chromosome of the strain. This process led to the formation of a new 188 kb fusion plasmid, which could be then subsequently transmitted to recipient strain Escherichia J53. The chromosomal MDR DNA fragment was shown to be flanked by one copy of IS element at each end and could be excised from the chromosome to form circular intermediate, which was then fused to pSa64-96kb and form a single plasmid through IS mediated homologous recombination. The role of IS on enhancing the efficacy of fusion and transmission of this chromosomal MDR DNA fragment was further proven in other strains. These findings showed that dynamic interaction between specific chromosomal fragment and plasmids may significantly enhance resistance development and transferability of mobile resistance-encoding elements among bacterial pathogens.
环丙沙星是治疗感染的一种选择，近年来其耐药性急剧增加，尤其是在德比血清型中，大多数菌株携带染色体编码的多重质粒介导喹诺酮耐药（PMQR）基因。在这项研究中，我们在一株德比分离株（即Sa64）中发现了一种接合质粒pSa64 - 96kb，它可以提取并融合到一个含有两个PMQR基因（qnrS和aac(6')-Ib-cr）的多重耐药（MDR）DNA片段上，这两个基因位于该菌株的染色体上。这个过程导致形成了一个新的188 kb融合质粒，随后它可以被转移到受体菌株大肠杆菌J53中。结果表明，染色体MDR DNA片段两端各有一个IS元件拷贝，它可以从染色体上切除形成环状中间体，然后通过IS介导的同源重组与pSa64 - 96kb融合形成单一质粒。IS在增强该染色体MDR DNA片段融合和转移效率方面的作用在其他菌株中也得到了进一步证实。这些发现表明，特定染色体片段与质粒之间的动态相互作用可能会显著增强细菌病原体中移动耐药编码元件的耐药性发展和转移性。
