Investigation of the carbapenem resistance genes and the clonal relationships of the carbapenem resistant klebsiella pneumoniae strains in A University Hospital

Aim: Klebsiella pneumoniae is among the leading human pathogens. The carbapenem resistance, particularly seen in the strains from the nosocomial infections, significantly limits the treatment options. Knowing the molecular dynamics of this resistance is important for development of the control measurements intended to prevent the emergence of carbapenem resistance in Klebsiella strains and to reduce the spreading of such resistant strains. In this study, previously determined carbapenemase genes and the clonal relationships of the carbapenem resistant K. pneumonia strains isolated from clinical samples were aimed to be investigated. Material and Methods: In this cross sectional study, the carbapenem resistant K. pneumoniae strains which were isolated from the clinical samples between January 2012 and June 2014 in the medical microbiology laboratory of our hospital were included. Strains were prospectively collected, the carbapenem resistance was determined with ertapenem disc and Modified Hodge test, and imipenem MICs of these strains were studied with Etest method. Carriage of the carbapenemase genes including OXA-48, NDM, VIM, IMP, and KPC were determined with in-house PCR, and clonal relationships of the strains was studied with Pulsed Field Gel Electrophoresis (PFGE). Results: AAim: Klebsiella pneumoniae is among the leading human pathogens. The carbapenem resistance, particularly seen in the strains from the nosocomial infections, significantly limits the treatment options. Knowing the molecular dynamics of this resistance is important for development of the control measurements intended to prevent the emergence of carbapenem resistance in Klebsiella strains and to reduce the spreading of such resistant strains. In this study, previously determined carbapenemase genes and the clonal relationships of the carbapenem resistant K. pneumonia strains isolated from clinical samples were aimed to be investigated. Material and Methods: In this cross sectional study, the carbapenem resistant K. pneumoniae strains which were isolated from the clinical samples between January 2012 and June 2014 in the medical microbiology laboratory of our hospital were included. Strains were prospectively collected, the carbapenem resistance was determined with ertapenem disc and Modified Hodge test, and imipenem MICs of these strains were studied with Etest method. Carriage of the carbapenemase genes including OXA-48, NDM, VIM, IMP, and KPC were determined with in-house PCR, and clonal relationships of the strains was studied with Pulsed Field Gel Electrophoresis (PFGE). Results: A total 70 carbapenem resistant K. pneumoniae were identified throughout the study. With the molecular analysis, at least one carbapenemase gene was determined in 61 (87.1%) strains, and there was no studied genes in any of the remaining 9 (12.9%) strains. After the analyses, blaOXA-48 was found in 51 (72.8%) strains, blaNDM in 11 (15.7%) strains, and blaVIM in 3 (4.2%) strains; and it was observed that 4 (7.8%) strains harboring blaOXA-48 were also carrying blaNDM. blaIMP and blaKPC were not determined any of the studied strains. With the Etest MIC analyses, imipenem MICs of 23 (32.8%) of the 70 studied strains were found under the susceptibility breakpoint (<4 μg/ml), and total MIC distribution of the included strains was between 0.125-32 μg/ml. A total 67 of 70 studied K. pneumoniae strains showed 59 different PFGE profile and remaining 3 strains didn't produce a meaningful band pattern. Clonally related strains were collected in 4 different cluster, and the clustering rate of all strains was found as 18%. The largest cluster was genotype 58 consisting 5 strains, followed by genotype 34 consisting 3 strains and genotype 29 including 2 strains.Discussion and Conclusion: According to results of this study, OXA-48 and NDM type carbapenemases were responsible for the majority of carbapenem resistance in the Klebsiella strains in our hospital. This data is very similar to the data previously reported from our country. Though this study was performed in a single center, the strains showing a highly heterogenic genetic distribution was a significant evidence of proving that these resistance genes spreading between different genetic clones.