Adaptation of IncX3 plasmid encoding blaNDM-4 within broad host range: A study from India

Abstract

Different variants of blaNDM has been reported across Indian subcontinent within diverse host range of gram negative bacilli. Most of their transferability depends on types of plasmid that encodes resistance determinant. IncX type plasmid is more recently known for carrying carbapenem resistance and NDM-4 variant is considered to have better hydrolytic property. This study aims to investigate the maintenance and stability of blaNDM-4 within BHR and transcriptional response. E.coli of clinical origin that harbor blaNDM-4 within IncX3 plasmid were used. Six different hosts were selected for gene transfer experiment, two strains of E.coli, K.pneumoniae, P.mirabilis, A.baumannii and P.aeruginosa. All the transformants and parent isolate were subjected for stability within new host. IncX3 plasmid encoding blaNDM-4 was transferred in host when imipenem (0.5µg/ml) screen agar was used for selection of transformants which are coharbouring resistance for aminoglycosides and quinolone. Plasmid was successfully expanded within all the six recipients till 55th serial passages. Transcriptional expression with NDM gene was variable for parent isolates though for new hosts it was showing random increased pattern in Proteus, E.coli, and DH5α. This could highlight, external carbapenem pressure helps in maintenance and expression of blaNDM-4 within different host range and epidemiological significance and will help in tracking the genetic vehicle responsible for their transmission,restricting their spread.