Objective: Carbapenem-resistant Klebsiella pneumoniae restricts treatment options and increases mortality and morbidity. Strains harboring multiple carbapenemases have emerged as a new phenomenon posing a serious threat, like the hidden part of an iceberg. We aimed to evaluate the carbapenemase resistance genes distribution and clonal relationships in our isolates.

Methods: The study included 69 meropenem-resistant K. pneumoniae isolates obtained from blood cultures in 2024. The isolates were identified using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Bacterial DNA was obtained using the DNeasy Blood and Tissue Kit (Qiagen, Germany). PCR reactions were performed using the DreamTaq Green PCR Master Mix kit (Thermo Scientific Chemicals, USA). Clonality was determined by pulsed-field gel electrophoresis.

Results: Of the isolates, 46 (66.7%) were from intensive care units and 23 (33.3%) from the clinical wards. All isolates were resistant to ertapenem, meropenem, amoxicillin clavulanate, piperacillin tazobactam, cefuroxime, and ciprofloxacin. Susceptibility of ceftazidime-avibactam and colistin were 43.5% (n=30) and 34.8% (n=24). At least one carbapenemase gene was detected in all isolates. In the isolates, blaOXA-48, blaKPC, and blaNDM-1 were detected at the rates of 23.2%, 23.2%, and 7.2%, respectively. blaOXA-48 and blaNDM-1 were coexisted in 32 (46.4%) isolates. In pulsed-field gel electrophoresis analysis, 46 different genotypes and nine different clusters were identified.

Conclusion: K. pneumoniae strains harboring multiple carbapenemase genes severely limit current treatment options and pose a significant threat to public health. To prevent the spread of these strains, it is necessary to shed light on the mechanisms and to sustain active surveillance efforts with rigorousness.