Carbapenem resistance determinants in Klebsiella pneumoniae strains isolated from blood cultures-comparative analysis of molecular and phenotypic methods

Abstract

Introduction: This study provides data on carbapenemases identified in carbapenem-resistant Klebsiella pneumoniae (CR-KP) isolated from blood-cultures by the multiplex molecular method. Material and method: Between October 2016 and September 2017, 47 non-duplicate Klebsiella pneumoniae (KP) were isolated from blood cultures, from hospitalized patients in the Regional Institute of Gastroenterology and Hepathology, Cluj-Napoca, Romania. Identification and antimicrobial susceptibility tests (AST) were performed by Vitek 2 Compact. The combination disks test (CDT) was used for phenotypic analysis and the LightCycler® Multiplex DNA assay was used to detect and identify the carbapenemases by the LightCycler®z 480 Instrument. The following targets were chosen: blaKPC, blaNDM, blaGES, blaIMP and blaOXA-48 genes and the Cobas® 4800 software variant 2.2.0 was used for the results interpretation. Results: Taking into consideration the meropenem minimum inhibitory concentration (MIC), 29 KP were susceptible and 18 were not-susceptible (MIC≥0.5 µg ml-1). In the CR-KP group, the CDT identified OXA-48 (10/18) and KPC (7/18) producers. One isolate showed a noninterpretable profile. The multiplex molecular analyses confirmed the carbapenemases production as: 9 CR-KP were KPC and OXA-48 co-producers, 8 were OXA-48 and one was KPC producing strains. In CR-KP group, we found a significant correlation between the CDT and RT-PCR tests results, concerning KPC (p = 0.671). Eight phenotypic results were confirmed by molecular Light-Cycler® Multiplex DNA assay. For CR-KP co-producers (KPC and OXA-48), the CDT could indicate only one carbapenem-hydrolyzing enzyme. Conclusion: This study highlights the CR-KP co-producers (OXA-48 and KPC). OXA-48-like is more frequently encountered in our area than other carbapenemases.