To investigate the molecular mechanisms of reduced carbapenem susceptibility in Klebsiella pneumonia.One reduced carbapenem susceptible Klebsiella pneumonia clinical isolate was investigated. Kirby-Bauer disc test was applied to determine the antibiotic susceptibility of the isolate. Modified Hodge Test and EDTA-disk synergy test were used to confirm whether this Klebsiella pneumonia strain could produce metallo-beta-lactamase. The genotype of the beta-lactamase was confirmed by PCR and DNA sequence analysis. Plasmid DNA preparations and conjugation experiment were used to determine the location of the resistant gene.Antibacterial circle of imipenem, meropenem for Klebsiella pneumonia isolate were 16 cm and 17 cm implied that the isolated strain producing carbapenemas. Modified Hodge Test and EDTA-disk synergy test confirmed that this Klebsiella pneumonia isolate produced metallo-beta-lactamase. IMP-4 gene was amplified by PCR and confirmed with sequence analysis. A reduced carbapenem susceptibility in obtained conjugants was observed when evaluated with Kirby-Bauer disc test and conjugation experiment also revealed that blalMP-4 were carried on one plasmid with a size of approximately 73 000 bp.Production of plasmid-mediated metallo-beta lactamase IMP-4 might lead to the reduced susceptibility of Klebsiella pneumonia spp. to carbapenems.