Xing-Ping Li1, Ruan-Yang Sun2, Jia-Qi Song2, Liang-Xing Fang2, Rong-Min Zhang2, Xin-Lei Lian2, Xiao-Ping Liao2, Ya-Hong Liu2, Jun Lin3, Jian Sun4. 1. National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, P. R. China; College of Veterinary Medicine, South China Agricultural University, Guangzhou, P. R. China; Department of Animal Science, The University of Tennessee, Knoxville, TN, USA. 2. National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, P. R. China; College of Veterinary Medicine, South China Agricultural University, Guangzhou, P. R. China. 3. Department of Animal Science, The University of Tennessee, Knoxville, TN, USA. Electronic address: jlin6@utk.edu. 4. National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, P. R. China; College of Veterinary Medicine, South China Agricultural University, Guangzhou, P. R. China. Electronic address: jiansun@scau.edu.cn.
Abstract
OBJECTIVES: To characterize the colistin-resistant bacterial population in the gut and assess diversity of mcr-1 transmission within a single individual. METHODS: Large numbers of isolates (>100 colonies/chicken cecum sample) were collected from nine randomly selected mcr-1-positive chickens in China and used for comprehensive microbiological, molecular and comparative genomics analyses. RESULTS: Of 1273 colonies, 968 were mcr-1 positive (962 Escherichia coli, two Escherichia fergusonii, two Klebsiella pneumoniae and two Klebsiella quasipneumoniae). One to six colistin-resistant species and three to 10 E. coli pulsed-field gel electrophoresis (PFGE) clusters could be identified from each sample. Whole-genome sequencing (WGS) analysis of the representative E. coli strains revealed three to nine sequence types observed in a single chicken host. The mcr-1 genes are located in either chromosomes or plasmids of different types, including IncI2 (n=30), IncHI2 (n=14), IncX4 (n=4), p0111(n=2) and IncHI1(n=1). Strikingly, in single cecum samples, one to five Inc type plasmids harbouring mcr-1 could be identified. Great diversity was also observed for the same IncI2 plasmid within a single chicken host. In addition, up to eight genetic contexts of the mcr-1 gene occurred within a single chicken. CONCLUSIONS: There is extensive heterogeneity and flexibility of mcr-1 transmission in chicken gut due to bacterial species differences, distant clonal relatedness of isolates, many types and variations of mcr-positive plasmids, and the flexible genetic context of the mcr-1 gene. These compelling findings indicate that the gut is a 'melting pot' for active horizontal transfer of the mcr-1 gene.
OBJECTIVES: To characterize the colistin-resistant bacterial population in the gut and assess diversity of mcr-1 transmission within a single individual. METHODS: Large numbers of isolates (>100 colonies/chicken cecum sample) were collected from nine randomly selected mcr-1-positive chickens in China and used for comprehensive microbiological, molecular and comparative genomics analyses. RESULTS: Of 1273 colonies, 968 were mcr-1 positive (962 Escherichia coli, two Escherichia fergusonii, two Klebsiella pneumoniae and two Klebsiella quasipneumoniae). One to six colistin-resistant species and three to 10 E. coli pulsed-field gel electrophoresis (PFGE) clusters could be identified from each sample. Whole-genome sequencing (WGS) analysis of the representative E. coli strains revealed three to nine sequence types observed in a single chicken host. The mcr-1 genes are located in either chromosomes or plasmids of different types, including IncI2 (n=30), IncHI2 (n=14), IncX4 (n=4), p0111(n=2) and IncHI1(n=1). Strikingly, in single cecum samples, one to five Inc type plasmids harbouring mcr-1 could be identified. Great diversity was also observed for the same IncI2 plasmid within a single chicken host. In addition, up to eight genetic contexts of the mcr-1 gene occurred within a single chicken. CONCLUSIONS: There is extensive heterogeneity and flexibility of mcr-1 transmission in chicken gut due to bacterial species differences, distant clonal relatedness of isolates, many types and variations of mcr-positive plasmids, and the flexible genetic context of the mcr-1 gene. These compelling findings indicate that the gut is a 'melting pot' for active horizontal transfer of the mcr-1 gene.
Authors: Ebenezer Foster-Nyarko; Nabil-Fareed Alikhan; Anuradha Ravi; Nicholas M Thomson; Sheikh Jarju; Brenda A Kwambana-Adams; Arss Secka; Justin O'Grady; Martin Antonio; Mark John Pallen Journal: Microb Genom Date: 2020-11-30
Authors: Carlos Bastidas-Caldes; Jacobus H de Waard; María Soledad Salgado; María José Villacís; Marco Coral-Almeida; Yoshimasa Yamamoto; Manuel Calvopiña Journal: Pathogens Date: 2022-06-08