Investigation of Carbapenemase Genes and Clonal Relationship in Carbapenem Resistant Klebsiella pneumoniae Strains

Abstract

Objective:Resistant Gram-negative bacteria isolated from health-related infections are a worldwide problem. Increasing frequency of infections particularly caused by Enterobacteriaceae producing expanded spectrum beta lactamase, leads to the use of more carbapenem group antibiotics which, in turn, leads to bacterial resistance. In this study, we aimed to evaluate carbapenem resistance in Klebsiella pneumoniae (K. pneumoniae) isolates, the mechanisms causing this resistance and the clonal relationship between these isolates.Methods:Ninety one K. pneumoniae strains isolated from clinical samples obtained in our laboratory were included to the study. The identification of the bacteria was performed with Matriks assisted laser desorption ionization time of flight mass spectrometry (bioMérieux, Marcy-I’Étoile, France) and antimicrobial susceptibility with VITEK-2 (bioMérieux), and the carbapenem resistance was confirmed by ertapenem E-test (bioMérieux). Reverse transcription polymerase chain reaction method was used for the investigation of genes causing carbapenemase production (blaOXA-48, blaNDM-1, blaKPC, blaIMP, blaVIM-1). The clonal relationship between isolates was investigated by pulsed-field jel elektroforez.Results:In carbapenem resistant isolates, blaOXA-48 positivity was found to be 55%, blaNDM-1 positivity 37.4%, blaKPC and blaVIM-1 positivity 1.1%. A total of 10 isolates was identified with different resistance genes. In 73 of the isolates included in the study, the clonal relationship was examined, and 16 different groups were identified. Twenty isolates were not clonally associated with any other isolates. The most common resistance mechanism causing the carbapenem resistance was blaOXA-48 gene that is known to be endemic in Turkey.Conclusion:As a result, the carbapenem resistance that we found as 3.13% in our study is similar to the rates obtained in other studies performed in our country which indicates that this resistance is not at a high level yet in our country. However, the ability of carbapenem resistance genes to spread between strains can be a major problem in the near future. Molecular methods are gold standard in carbapenemase detection, but because of having high cost they can not be used in laboratories routinely. Modified Hodge test or carbapenemase inactivation test are alternative tests with low costs that can be used in the determination of carbapenemase.

Keywords

• Resistance gene
• carbapenem
• Klebsiella pneumoniae
• pulsed-field gel electrophoresis