Letter to the Editor: Surveillance of mcr-1 and mcr-2 genes in Carbapenem-resistant Klebsiella pneumoniae strains from an Italian Hospital

To the editor: In a recent editorial [1], Kluytmans reports on the rise of plasmid-mediated colistin resistance that has occurred worldwide since its first description in 2016 [2]. Antimicrobial resistance, especially in Gram-negative bacteria, has been recognised as a serious threat to human health, and colistin, as well as tigecycline, is often the only therapeutic option for infections caused by carbapenem-resistant Enterobacteriaceae (CRE). Resistance to colistin can occur in Enterobacteriaceae either through adaptive chromosomal mutations that alter the bacterial outer membrane, or through plasmid-mediated horizontal gene transfer. The recently recognised global distribution of plasmid-borne colistin resistance determinants mcr-1,mcr-2, mcr-3 and mcr-4 represent a concern for infection prevention and public health , especially in the context of high CRE prevalence in hospital wards [3-5].