Plasmid-mediated mcr-1 in carbapenem-susceptible Escherichia coli ST156 causing a blood infection: an unnoticeable spread of colistin resistance in Brazil?

OBJECTIVE

We describe an IncX4 pHC891/16mcr plasmid carrying mcr-1 in a colistin-resistant and carbapenem-susceptible E. coli isolate (HC891/16), ST156, which caused a blood infection in a Brazilian patient with gallbladder adenocarcinoma.

METHODS

Strain HC891/16 was subjected to whole genome sequencing using the MiSeq Platform (Illumina, Inc., USA). Assembly was performed using Mira and ABACAS.

RESULTS

The isolates showed resistance only to ciprofloxacin, ampicillin and cefoxitin, and whole-genome sequencing revealed the presence of aac(6')Ib-cr and blaTEM1.

CONCLUSIONS

Our findings warn of the possible silent dissemination of colistin resistance by carbapenem-susceptible mcr-1 producers, as colistin susceptibility is commonly tested only among carbapenem-resistant isolates.