Abstract
Objectives: The current study was aimed to investigate the adaptability and stability of blaNDM-4 within a broad host range and transcriptional response.<br>Methods: Six isolates of Escherichia coli, harboring blaNDM-4 were confirmed by PCR sequencing of the whole gene. Transformation and conjugation assay were carried out and plasmid incompatibility was determined by PCR assay. The serial passage was done for consecutive 70 days without any antibiotic pressure for both parent strain and transformants. Transcriptional expression of blaNDM-4 within a broad host range against concentration gradient imipenem stress was studied.<br>Results: IncX3 plasmid encoding blaNDM-4 was successfully transferred in six different hosts when imipenem (0.5 µg/ml) screen agar was used for the selection of transformants. It was also found to harbor resistance for aminoglycosides and quinolone. When checked for stability, it was observed that the plasmid was successfully expanded within all six recipients for 55th serial passages. Transcriptional expression with IncX3 was random but at a consistent level for wild type and without concentration gradient stress of imipenem. Transcriptional expression with NDM gene was variable for parent isolates though for new hosts it was showing randomly increased patterns in Proteus, E. coli, and DH5α.<br>Conclusion: The present study could highlight that external carbapenem pressure helps in the maintenance and expression of blaNDM-4 within different host range. This study is of epidemiological significance and will help in tracking the genetic vehicle responsible for their transmission by restricting their spread. J Microbiol Infect Dis 2021; 11(2):75-81.

Key words: Broad host range, NDM, Transcriptional expression