BackgroundAntibiotics exert an outstanding selective pressure on bacteria, forcing their chromosomal gene mutations and drug resistance genes to spread. The objective of this study is to evaluate the expression of the New Delhi Metallo-β-Lactamase-1 gene (blaNDM−1) in the clinical isolate (Klebsiella pneumoniaeTH-P12158), transformant strainsEscherichia coliBL21 (DE3)-blaNDM−1, andEscherichia coliDH5α-blaNDM−1when exposed to imipenem.Methodsβ-Lactamase genes (blaSHV,blaTEM−1,blaCTX−M−9,blaIMP,blaNDM−1,blaKPC,blaOXA,blaGES, andblaDHA) from randomly selected carbapenems-sensitiveK.pneumoniae(n = 20) andE.coli(n = 20) strains were amplified by PCR. The recombinant plasmid of pET-28a harboringblaNDM−1was transformed intoE.coliBL21 (DE3) andE.coliDH5α by electroporation. The resistance phenotype and higherblaNDM−1expression inK.pneumoniaeTH-P12158, transformantE.coliBL21 (DE3)-blaNDM−1, andE.coliDH5α-blaNDM−1were observed when exposed to imipenem with grade increasing, decreasing, and canceling doses, respectively.ResultsAfter being exposed to different doses of imipenem, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of antimicrobial drugs andblaNDM−1expression of strains increased, which was positively correlated with doses of imipenem. On the contrary, with the decrease or cancellation of imipenem doses, theblaNDM−1expression was deteriorated, while the MIC and MBC values remained relatively stable. These results demonstrated that low doses of imipenem (˂MIC) could pressblaNDM−1positive strains producing stable drug resistance memory and alteredblaNDM−1expression.ConclusionsLow doses of imipenem could pressblaNDM−1positive strains producing sustained resistance memory and alteredblaNDM−1expression. In particular, the positive correlation between the resistance genes expression and antibiotics exposure shows promising guiding significance for clinical medication.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12941-023-00598-8.