Genomic characteristics and antibiotic-resistant mechanisms of plasmid pB557-NDM isolate from Enterbacter cloacae / 军事医学

ABSTRACT

Objective To characterize the whole-sequence of plasmid pB557-NDM isolate from Enterbacter cloacae and elaborate its antibiotic-resistant mechanisms .Methods Antibiotic resistance genes were determined by PCR , followed by amplicon sequencing .The activity of class A/B/D carbapenemases was determined by modified Carba NP test .Conjugation experiments were performed to verify the transferability of plasmid pB 557-NDM.The minimum inhibitory concentration (MIC) values of bacterial strains were tested using VITEK 2.The genetic structure, mobile elements and antibiotic-resistant mechanisms of transferable plasmid pB 557-NDM were determined by a whole genome sequencing method .Results The modified CarbaNP test showed that B557 and B557-EC600 had class B carbapenemase activity , and that the blaNDM was carried by plasmid pB557-NDM.This plasmid could be transferred into E.coli through conjugation experiments and therefore could confer corresponding antibiotic resistances to the transconjugant B 557-EC600.Plasmid pB557-NDM was an IncA/C2 plasmid, whose total length was 141.65 kb, and the GenBank accession number was KX786648.It had two inserted regions.One was the blaCMY-6 region where the blaCMY gene was carried by a transposition unit IS Ecp1-blaCMY , the other was the blaNDM-1 region which consisted of a ΔTn1696-In46-rmtC-ISKpn14-ΔTn125 complex structure.Conclusion The production of plasmid pB557-NDM in strain B557 contributes most to its high resistance to many antibiotics .The blaNDM-1 gene is carried in a trancated transposition ΔTn125.