Ruichao Li1,2, Pei Zhang3,4, Xiaorong Yang5, Zhiqiang Wang1, Séamus Fanning4,6, Juan Wang7, Pengcheng Du8, Li Bai4. 1. Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, P. R. China. 2. Institute of Comparative Medicine, Yangzhou University, Yangzhou, Jiangsu Province, P. R. China. 3. Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University, Guangzhou, P. R. China. 4. Key Laboratory of Food Safety Risk Assessment, National Health Commission of the People's Republic of China, China National Center for Food Safety Risk Assessment, Beijing, P. R. China. 5. Center for Disease Control and Prevention of Sichuan Province, Chengdu, P. R. China. 6. UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield, Dublin D04 N2E5, Ireland. 7. College of Veterinary Medicine, Northwest A&F University, No. 22 Xinong Road, Yangling 712100, Shaanxi, P. R. China. 8. Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, and Beijing Key Laboratory of Emerging Infectious Diseases, Beijing, P. R. China.
Abstract
OBJECTIVES: To characterize the genome of an Escherichia coli harbouring both mcr-1 and mcr-3.19 on a hybrid plasmid and the underlying transmission mechanisms. METHODS: Broth microdilution was used to perform antimicrobial susceptibility testing. Conjugation assays and S1-PFGE were used to assess the transferability of mcr genes. Resistance genotypes and genetic contexts were investigated, based on WGS data from the Illumina and MinION platforms. Inverse PCR was performed to test the mcr-3.19-bearing circular intermediate. Bioinformatic tools were used to further characterize the hybrid plasmid. RESULTS: E. coli CP53 was identified as harbouring both mcr-1 and mcr-3.19 on a 231 859 bp hybrid plasmid pCP53-mcr1_3 containing IncFIA, IncHI1A, IncHI1B and IncN replicons. The genetic structures of mcr-1 and mcr-3.19 were similar to those reported in other mcr-1 and mcr-3.19-bearing plasmids, which suggested that recombination between mcr-bearing plasmids had been mediated by ISs. However, the MDR plasmid pCP53-mcr1_3 cannot transfer via conjugation. Furthermore, another three plasmids were identified in the isolate, two of which encoded resistance genes. In640 duplication between two MDR plasmids was observed. An MDR-region recombination existed in E. coli CP53. A core structure consisting of mcr-3-dgkA existed in mcr-3-bearing plasmids reported, to date. Circular intermediates were observed for mcr-1 and mcr-3.19 regions. CONCLUSIONS: A novel mcr-3.19 was identified along with mcr-1 contained in a hybrid plasmid. This finding suggested that evolution of mcr genes among various plasmids was being driven by mobile elements. Molecular surveillance of mcr gene co-occurrence warrants further investigation to evaluate the public health risk.
OBJECTIVES: To characterize the genome of an Escherichia coli harbouring both mcr-1 and mcr-3.19 on a hybrid plasmid and the underlying transmission mechanisms. METHODS: Broth microdilution was used to perform antimicrobial susceptibility testing. Conjugation assays and S1-PFGE were used to assess the transferability of mcr genes. Resistance genotypes and genetic contexts were investigated, based on WGS data from the Illumina and MinION platforms. Inverse PCR was performed to test the mcr-3.19-bearing circular intermediate. Bioinformatic tools were used to further characterize the hybrid plasmid. RESULTS:E. coli CP53 was identified as harbouring both mcr-1 and mcr-3.19 on a 231 859 bp hybrid plasmid pCP53-mcr1_3 containing IncFIA, IncHI1A, IncHI1B and IncN replicons. The genetic structures of mcr-1 and mcr-3.19 were similar to those reported in other mcr-1 and mcr-3.19-bearing plasmids, which suggested that recombination between mcr-bearing plasmids had been mediated by ISs. However, the MDR plasmid pCP53-mcr1_3 cannot transfer via conjugation. Furthermore, another three plasmids were identified in the isolate, two of which encoded resistance genes. In640 duplication between two MDR plasmids was observed. An MDR-region recombination existed in E. coli CP53. A core structure consisting of mcr-3-dgkA existed in mcr-3-bearing plasmids reported, to date. Circular intermediates were observed for mcr-1 and mcr-3.19 regions. CONCLUSIONS: A novel mcr-3.19 was identified along with mcr-1 contained in a hybrid plasmid. This finding suggested that evolution of mcr genes among various plasmids was being driven by mobile elements. Molecular surveillance of mcr gene co-occurrence warrants further investigation to evaluate the public health risk.