Emergence of carbapenem-resistant Enterobacter hormaechei ST93 plasmids co-harbouring blaNDM-1, blaKPC-2, and mcr-9 in bloodstream infection

Abstract

We isolated a strain of Enterobacter hormaechei, ECC2783, coharbouring blaNDM-1, blaKPC-2 and mcr-9 plasmids in bloodstream infection and investigated its biological features. The presence of carbapenemase genes and mcr-9 was comfirmed by polymerase chain reaction (PCR) amplification. Whole genome sequencing and genomic analysis were performed on ECC2783. Conjugation and stability of plasmids carrying the carbapenemase gene experiments were performed. We also performed a colistin resistance induction experiment and studied the fitness cost of transconjugants. ECC2783 has an extensive drug resistance (XDR) phenotype. Multilocus sequence typing analysis results show that ECC2783 is sequence type 93. Bioinformatic analysis confirmed that ECC2783 has four plasmids of which pECC2783_a carrying mcr-9 is the IncHI2 type, and pECC2783_c carrying blaNDM-1 is the IncX3 type. pECC2783_d carrying blaKPC-2 is an unclassified type. We successfully obtained two transconjugants (J53/ECC2783_1 carrying blaNDM-1 and J53/ECC2783_2 carrying blaKPC-2 and blaNDM-1). There was no statistically significant difference in the relative growth rate between J53 and J53/ECC2783_2. For the first time, we isolated a carbapenem-resistant E. hormaechei plasmids coharbouring blaNDM-1, blaKPC-2 and mcr-9 in a BSI patient. This isolate has the advantage of survival in a hospital environment, and its clinical monitoring should be strengthened.