Resistance to ciprofloxacin, a treatment choice for Salmonella infections, has increased dramatically in recent years in particular in serotype Salmonella 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 Salmonella Derby isolate, namely Sa64, which could extract and fuse to a multiple drug resistance (MDR) DNA fragment containing two PMQR genes, aac(6’)-Ib-cr, and qnrS2 located on the chromosome of the Salmonella strain. This process led to the formation of a new 188 kb fusion plasmid, which could be then subsequently transmitted to recipient strain Escherichia coli J53. The chromosomal MDR DNA fragment was shown to be flanked by one copy of IS26 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 IS26 mediated homologous recombination. The role of IS26 on enhancing the efficacy of fusion and transmission of this chromosomal MDR DNA fragment was further proven in other Salmonella 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.

对环丙沙星的耐药性，一种环丙沙星的治疗选择 沙门氏菌 感染，近年来特别是血清型急剧增加 沙门氏菌德比大多数菌株携带染色体编码的多个质粒介导的喹诺酮抗性（PMQR）基因。在这项工作中，我们发现了一个质粒pSa64-96kb沙门氏菌 Derby分离物，即Sa64，可以提取并融合成包含两个PMQR基因的多药抗性（MDR）DNA片段， aac（6'）-Ib-cr和 qnrS2 位于染色体上 沙门氏菌应变。这个过程导致了一个新的188 kb融合质粒的形成，随后可以将其传递给受体菌株埃希氏菌大肠杆菌J53。染色体MDR DNA片段的侧面显示为一份IS26 分子的两端可被切割，形成环状中间体，然后与pSa64-96kb融合并通过IS形成单个质粒26介导的同源重组。IS的作用26 关于增强该染色体MDR DNA片段融合和传播的功效的研究已在其他 沙门氏菌株。这些发现表明，特定染色体片段和质粒之间的动态相互作用可以显着增强细菌病原体之间的抗性发展和移动抗性编码元件的转移能力。