mcr-1 Gene Has No Effect on Colistin Resistance When It Coexists with Inactivated mgrB Gene in Klebsiella pneumoniae.

The inactivated mgrB gene and the mcr-1 gene are important mechanisms of colistin resistance in Klebsiella pneumoniae and they are threats to the clinical use of colistin. In this study, mcr-1 gene was cloned into K. pneumoniae strains (XH209 and KP10) and their derived strains (XH209 M and KP10 M), which showed high-level resistance to colistin. The acquisition of the mcr-1 gene led to colistin resistance in XH209 and KP10, but the addition of mcr-1 gene did not cause change of colistin minimum inhibitory concentrations in the XH209 M and KP10 M. In addition, the impact of mcr-1 gene on growth rate showed strain specific in K. pneumoniae. In conclusion, the mcr-1 gene does not cause the same level of colistin resistance as the inactivated mgrB gene in K. pneumoniae. The mcr-1 gene has no effect on colisitin resistance when it coexists with inactivated mgrB gene in K. pneumoniae.