Analysis of serial isolates of mcr-1-positive Escherichia coli reveals a highly active ISApl1 transposon

Erik Snesrud, Ana C. Ong, Brendan Corey, Yoon I. Kwak, Robert Clifford, Todd Gleeson, Shannon Wood, Timothy J. Whitman, Emil P. Lesho, Mary Hinkle, Patrick McGann*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


The emergence of a transferable colistin resistance gene (mcr-1) is of global concern. The insertion sequence ISApl1 is a key component in the mobilization of this gene, but its role remains poorly understood. Six Escherichia coli isolates were cultured from the same patient over the course of 1 month in Germany and the United States after a brief hospitalization in Bahrain for an unconnected illness. Four carried mcr-1 as determined by real-time PCR, but two were negative. Two additional mcr-1-negative E. coli isolates were collected during follow-up surveillance 9 months later. All isolates were analyzed by whole-genome sequencing (WGS). WGS revealed that the six initial isolates were composed of two distinct strains: an initial ST-617 E. coli strain harboring mcr-1 and a second, unrelated, mcr-1-negative ST-32 E. coli strain that emerged 2 weeks after hospitalization. Follow-up swabs taken 9 months later were negative for the ST-617 strain, but the mcr-1-negative ST-32 strain was still present. mcr-1 was associated with a single copy of ISApl1, located on a 64.5-kb IncI2 plasmid that shared >95% homology with other mcr-1 IncI2 plasmids. ISApl1 copy numbers ranged from 2 for the first isolate to 6 for the final isolate, but ISApl1 movement was independent of mcr-1. Some movement was accompanied by gene disruption, including the loss of genes encoding proteins involved in stress responses, arginine catabolism, and L-arabinose utilization. These data represent the first comprehensive analysis of ISApl1 movement in serial clinical isolates and reveal that, under certain conditions, ISApl1 is a highly active IS element whose movement may be detrimental to the host cell.

Original languageEnglish
Article numbere00056
JournalAntimicrobial Agents and Chemotherapy
Issue number5
StatePublished - May 2017
Externally publishedYes


  • Colistin
  • Mcr-1
  • Plasmids


Dive into the research topics of 'Analysis of serial isolates of mcr-1-positive Escherichia coli reveals a highly active ISApl1 transposon'. Together they form a unique fingerprint.

Cite this