Genome sequences of two clinical Escherichia coli isolates harboring the novel colistin-resistance gene variants mcr - 1
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Gut Pathogens Open Access
GENOME REPORT
Genome sequences of two clinical Escherichia coli isolates harboring the novel colistin‑resistance gene variants mcr‑1.26 and mcr‑1.27 Bernd Neumann1* , Wiebke Rackwitz1, Klaus‑Peter Hunfeld2, Stephan Fuchs1, Guido Werner1 and Yvonne Pfeifer1
Abstract Background: Colistin is still a widely used antibiotic in veterinary medicine although it is a last-line treatment option for hospitalized patients with infections caused by multidrug-resistant Gram-negative bacteria. Colistin resistance has gained additional importance since the recent emergence of mobile colistin resistance (mcr) genes. In the scope of a study on colistin resistance in clinical Escherichia coli isolates from human patients in Germany we characterized the mcr-1 gene variants. Results: Our PCR-based screening for mcr-carrying E. coli from German patients revealed the presence of mcr-1-like genes in 60 isolates. Subsequent whole-genome sequence-based analyses detected one non-synonymous muta‑ tion in the mcr-1 gene for two isolates. The mutations were verified by Sanger sequencing and resulted in amino acid changes Met1Thr (isolate 803-18) and Tyr9Cys (isolate 844-18). Genotyping revealed no relationship between the iso‑ lates. The two clinical isolates were assigned to sequence types ST155 (isolate 803-18) and ST69 (isolate 844-18). Both mcr-1 variants were found to be located on IncX4 plasmids of 33 kb size; these plasmids were successfully conjugated into sodium azide resistant E. coli J53 Azir in a broth mating experiment. Conclusions: Here we present the draft sequences of E. coli isolate 803-18 carrying the novel variant mcr-1.26 and isolate 844-14 carrying the novel variant mcr-1.27. The results highlight the increasing issue of transferable colistin resistance. Keywords: Colistin-resistance, mcr-1, Escherichia coli, IncX4 Background The spread of multidrug-resistant Gram-negative bacteria with resistance to carbapenem antibiotics is a serious threat for public health globally and has led to the reintroduction of colistin, also known as polymyxin E, as a treatment option of last resort [1]. The emergence of *Correspondence: [email protected] 1 Division of Nosocomial Pathogens and Antibiotic Resistance, Robert Koch Institute, Wernigerode, Germany Full list of author information is available at the end of the article
colistin resistance in Escherichia coli (E. coli), a gut commensal of humans and animals, also appearing as opportunistic pathogen, is due to chromosomal mutations or plasmid-mediated genes (mcr) that were first described in 2015 [2–4]. So far, a total of 10 different mcr genes (mcr-1–mcr-10) are known; each gene has its origin in a specific bacterial species [5]. The gene mcr-1 is most prevalent and 25 different mcr-1 variants based on single amino acid substitutions have been submitted to the NCBI database, as of March 2020.
© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution
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