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

Abstract

Objectives: We isolated a strain of Enterobacter hormaechei, ECC2783, co-harbouring bla_NDM-1, bla_KPC-2 and mcr-9 plasmids from a bloodstream infection and investigated its biological features.

Methods: The presence of carbapenemase genes and mcr-9 was confirmed by polymerase chain reaction amplification. Whole genome sequencing and genomic analysis were performed on ECC2783. Experiments assessing the conjugation and stability of plasmids carrying the carbapenemase gene were performed. We also performed a colistin resistance induction experiment and studied the fitness cost of transconjugants.

Results: ECC2783 has an extensive drug resistance phenotype. Multilocus sequence typing analysis results showed that ECC2783 belongs to sequence type 93. Bioinformatics analysis confirmed that ECC2783 has four plasmids, of which pECC2783_a, carrying mcr-9, is the IncHI2 type, and pECC2783_c, carrying bla_NDM-1, is the IncX3 type. pECC2783_d, carrying bla_KPC-2, is an unclassified type. We successfully obtained two transconjugants (J53/ECC2783_1, carrying bla_NDM-1, and J53/ECC2783_2, carrying bla_KPC-2 and bla_NDM-1). There was no statistically significant difference in the relative growth rate between J53 and J53/ECC2783_2.

Conclusion: For the first time, we isolated carbapenem-resistant E. hormaechei plasmids co-harbouring bla_NDM-1, bla_KPC-2, and mcr-9 from a patient with a blood stream infection. This isolate has a survival advantage in a hospital environment, and its clinical monitoring should be strengthened.

Keywords: Carbapenem resistance; Enterobacter hormaechei; Fitness cost; bla(KPC-2); bla(NDM-1); mcr-9.