Renjie Wu,1– 3,* Luchao Lv,1– 3,* Chengzhen Wang,1– 3 Guolong Gao,1– 3 Kaiyang Yu,1– 3 Zhongpeng Cai,1– 3 Yiyun Liu,1– 3 Jun Yang,1– 3 Jian-Hua Liu1– 4 1Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China; 2Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China; 3National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China; 4Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jian-Hua Liu, College of Veterinary Medicine, South China Agricultural University, Wushan Road 483, Guangzhou, 510642, People’s Republic of China, Email jhliu@scau.edu.cnPurpose: The objective of this study was to elucidate the characteristics and mechanism of formation of the fusion plasmid pHNSHP24 carrying mcr-1.1.Materials and Methods: mcr-1.1-bearing Escherichia coli SHP24 and the corresponding transconjugant were subjected to whole-genome sequencing (WGS) combining the Illumina and MinION platforms to obtain the complete sequences of the fusion plasmid and its original plasmids.Results: Complete sequence analysis and S1 nuclease-pulsed field gel electrophoresis (S1-PFGE) results indicated that E. coli SHP24 carried four plasmids: mcr-1.1-harboring phage-like plasmid pHNSHP24-3, F53:A-:B- plasmid pHNSHP24-4, pHNSHP24-1, and pHNSHP24-2. However, the plasmid pHNSHP24 carrying mcr-1.1 presents in the transconjugant differed from the four plasmids in the donor strain SHP24. Further analysis showed that pHNSHP24 may be the fusion product of pHNSHP24-3 and pHNSHP24-4 and is formed through a replicative transposition mechanism mediated by IS 26 in E. coli SHP24.Conclusion: This study is the first to report the fusion of an mcr-1.1-harboring phage-like pO111 plasmid and an F53:A-:B- plasmid mediated by IS 26. Our findings revealed the role of phage-like and fusion plasmids in the dissemination of mcr-1.1.Keywords: fusion plasmid, mcr-1.1, IS 26, pO111 plasmid
