Detection of carbapenemase genes in Klebsiella pneumoniae isolates

Abstract

Introduction Klebsiella pneumoniae is one of the leading causes of serious hospital-acquired infections worldwide among Enterobacteriaceae species. It is the most common producer of carbapenemases in many parts of the world.

Objective The aim of the study was to determine which enzymes were responsible for resistance to carbapenems in Klebsiella pneumoniae strains isolated at the Centre of Microbiology of Public Health Institute of Vojvodina.

Methods A total of 29 Klebsiella pneumoniae non-duplicated strains resistant to at least one carbapenem isolated from clinical samples of hospitalized patients between November 1st 2013 and April 30th 2014 were studied. The species identification and susceptibility were done using VITEK 2 (bioMérieux, Marcy-l’Étoile, France) system. Phenotypic conformation of carbapenemase production was done by double-disc synergy test. PCR technique was performed for detection of genes encoding production of carbapenemases (bls_KPC, bla_VIM, bla_NDM, bla_OXA-48).

Results Isolates of Klebsiella pneumoniae resistant to at least one carbapenem showed positive on double-disc synergy test between meropenem and dipicolinic acid. All strains positive in phenotypic test contained bla_NDM gene. In isolates resistant only to ertapenem, neither production of carbapenemases nor presence of genes encoding these enzymes were detected. Among these isolates, nine produced extended-spectrum β-lactamase.

Conclusion The presence of NDM metallo-β-lactamase was determined in all Klebsiella pneumoniae isolates resistant to at least one carbapenem.

Keywords: Klebsiella pneumoniae; carbapenem-resistance; NDM β-lactamase