First detection of mcr-1-producing Escherichia coli in Greece.

Objectives: In this communication, we describe the emergence of the mcr-1 colistin resistance gene in a blaCTX-M-32 extended-spectrum-β-lactamase-producing Escherichia coli isolate recovered from a pediatric patient in Greece.

Methods: Bacterial identification and antimicrobial susceptibility testing were performed with the VITEK2 automated system and broth microdilution. Detection of resistance genes, assignment to sequence type, in silico plasmid detection, and virulence factors were carried out using ResFinder, MLST 2.0, PlasmidFinder 2.1., and VirulenceFinder 2.0, respectively. PlasmidSPAdes v3.11.1 was used to assemble the plasmid contigs. The mcr-1.1-containing plasmid was analyzed for insertion sequence elements using ISfinder. Phylogenetically relevant sequences of the plasmid were identified using the Microbe BLASTN suite.

Results: The microorganism was assigned to sequence type 48 and carried four plasmids of different incompatibility groups. The specific mcr-1.1 allele was located in a 32.722 bp plasmid belonging to the IncX4 group with no additional resistance genes.

Conclusion: To the best of our knowledge, this is the first detection of mcr-1 in a human specimen in our country. A potential spread of mcr-1 in Greece is concerning because of the existing high rates of carbapenem resistance and colistin usage as a last resort regimen.