Comparison of the performance of phenotypic methods used to detect carbapenem resistance in Klebsiella Pneumoniae isolates from clinical specimens.
Abstract
Background
Rapid and accurate detection of carbapenemase-producing Klebsiella pneumoniae is essential for effective antimicrobial therapy and infection control, yet molecular methods remain costly and technically demanding. This two-center study, representing two different geographic regions of Turkey, compared the performance of four phenotypic carbapenemase-detection assays, the Carbapenem Inactivation Method (CIM), the modified CIM (mCIM), the simplified CIM (sCIM), and mCIM supplemented with ammonium bicarbonate (mCIM-A), against polymerase chain reaction (PCR), the reference standard.
Methods
A total of 100 carbapenem-resistant K. pneumoniae isolates collected between 2022 and 2023 from Karabuk Training and Research Hospital and Balikesir Ataturk State Hospital were tested with all four phenotypic assays and confirmed by PCR for carbapenemase genes.
Results
Average sensitivities across the two centers were 86% for CIM, 91% for mCIM, 91% for sCIM, and 94% for mCIM-A. False-negative results occurred most frequently among isolates carrying OXA-48 and OXA-48-combination genes.
Conclusion
Because Turkey is an OXA-48-endemic region, molecular testing should remain the first-line approach for carbapenemase detection; however, given their high sensitivity, the carbapenem inactivation method and its modifications, particularly mCIM-A, represent reliable, cost-effective alternatives that can be readily incorporated into routine clinical microbiology laboratory practice.