%A Wu,Renjie %A Yi,Ling-xian %A Yu,Lin-feng %A Wang,Jing %A Liu,Yiyun %A Chen,Xiaojie %A Lv,Luchao %A Yang,Jun %A Liu,Jian-Hua %D 2018 %J Frontiers in Microbiology %C %F %G English %K Escherichia coli,MCR-1,Colistin,Plasmid,fitness %Q %R 10.3389/fmicb.2018.00331 %W %L %M %P %7 %8 2018-February-27 %9 Original Research %+ Dr Jian-Hua Liu,Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University,China,jhliu@scau.edu.cn %# %! The impact of IncHI2, IncX4, and IncI2 plasmids on host fitness. %* %< %T Fitness Advantage of mcr-1–Bearing IncI2 and IncX4 Plasmids in Vitro %U https://www.frontiersin.org/articles/10.3389/fmicb.2018.00331 %V 9 %0 JOURNAL ARTICLE %@ 1664-302X %X The objective of this study was to assess the impact of diverse plasmids bearing colistin resistance gene mcr-1 on host fitness. Forty-seven commensal E. coli isolates recovered from the pig farm where mcr-1 was first identified were screened for mcr-1. mcr-1-bearing plasmids were characterized by sequencing. The fitness impact of mcr-1-bearing plasmids was evaluated by in vitro competition assays. Twenty-seven (57.5%) E. coli isolates were positive for mcr-1. The mcr-1 genes were mainly located on plasmids belonging to IncI2 (n = 5), IncX4 (n = 11), IncHI2/ST3 (n = 8), IncFII (n = 2), and IncY (n = 2). InHI2 plasmids also carried other resistance genes (floR, blaCTX−M, and fosA3) and were only detected in isolates from nursery pigs. Sequences of the representative mcr-1–bearing plasmids were almost identical to those of the corresponding plasmid types reported previously. An increase in the fitness of IncI2- and IncX4-carrying strains was observed, while the presence of IncHI2, IncFII and IncY plasmids showed a fitness cost although an insignificant fitness increase was initially observed in IncFII or IncY plasmids-containing strains. Acquisition of IncI2-type plasmid was more beneficial for host E. coli DH5α than either IncHI2 or IncX4 plasmid, while transformants with IncHI2-type plasmid presented a competitive disadvantage against IncI2 or IncX4 plasmid containing strains. In conclusion, IncI2, IncX4, and IncHI2 were the major plasmid types driving the dissemination of mcr-1 in this farm. Increased fitness or co-selection by other antimicrobials might contribute to the further dissemination of the three epidemic mcr-1–positive plasmids (IncI2, IncX4, and IncHI2) in this farm and worldwide.