Abstract
AIM: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major public health concern, particularly in immunocompromised and critically ill patients. Colistin and tigecycline are among the last-resort treatment options, while the primary driver of CRKP emergence is carbapenemase production, especially Klebsiella pneumoniae carbapenemase (KPC) and metallo-β-lactamase (MBL). A thorough understanding of its resistance mechanisms is essential for selecting the most effective antimicrobial therapy. This study aimed to evaluate the diagnostic accuracy of the modified Hodge test (MHT) and modified carbapenem inactivation method (mCIM) in detecting molecular resistance mechanisms in CRKP clinical isolates. MATERIAL AND METHODS: This exploratory study consisted of 65 CRKP isolates, which were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany). Antimicrobial susceptibility testing was performed using the BD Phoenix system. The test isolates were subjected to MHT and mCIM and later shipped to the Central Research Laboratory (CRL), Bengaluru, India, where they were subjected to polymerase chain reaction (PCR) and whole-genome sequencing (WGS). RESULTS: PCR detected bla(OXA-48-like) , bla(NDM-1) , bla (NDM-5), and bla(KPC) genes in 79.7%, 10.2%, 64.4%, and 1.7% CRKP isolates, respectively. The PCR results were concordant with WGS. The MHT demonstrated an overall sensitivity of 60.3%, specificity of 100%, positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 4.2% for detecting carbapenemase production. It showed the highest sensitivity and specificity for bla(KPC) (100%) and bla(OXA-48-like) (75%) genes, respectively, with the highest PPV for bla(OXA-48-like) (91.4%) and NPV for bla(KPC) (100%). However, agreement between MHT and PCR for carbapenemase detection was negligible (Kappa: 0.049, p=0.223). A minimal but statistically significant agreement was noted for bla(OXA-48-like) detection (Kappa: 0.314, p=0.007), while no significant agreement was observed for bla(NDM-1) , bla(NDM-5) , or bla(KPC) genes. The mCIM had an overall sensitivity of 3.63%, specificity of 100%, PPV of 100%, and NPV of 1.8%. It exhibited the highest sensitivity (4.3%) and specificity (100%) for bla(OXA-48-like) (genes), with the highest PPV for bla(OXA-48-like) (100%), and NPV for bla(KPC) (98.1%). No statistically significant agreement was found between mCIM and PCR for carbapenemase detection (Kappa: 0.001, p=0.850). CONCLUSIONS: Comprehensive assessment of the diagnostic accuracy of MHT and mCIM using WGS across a broad spectrum of multi-drug-resistant (MDR) organisms should be conducted at multiple centers to produce reliable data that can guide better clinical management of the patients.