Comparison of Different Methods for Detecting Carbapenemase Types in Enterobacterales Species

AIM: This study aims to compare different phenotypic methods for detecting carbapenemases in carbapenem-resistant Enterobacterales BACKGROUND: Carbapenemase-producing Enterobacterales, a major public health threat, require rapid and accurate detection to control their spread and ensure effective patient management. METHODS: A total of 120 Clinical isolates, including 22 carbapenem-sensitive and 98 carbapenem-resistant strains, were inluded. Identification and susceptibility testing were performed using the BD Phoenix M50 system, while carbapenem resistance genes were detected via multiplex PCR (Bioeksen, Turkiye). Phenotypic methods applied included CIM, mCIM, combination disk test (Bioanalyse, Turkiye) and the RESIST-5 rapid test (Coris Bioconcept, Belgium). Sensitivity and specificity were calculated using molecular method as the gold standard. RESULTS: Carbapenem resistance genes were detected in all 98 resistant isolates, with KPC being the most prevalent (71.42%), followed by OXA-48 (21.42%) and NDM (14.2%). Multiple gene positivity was observed in 11.22% of isolates. The CIM test showed 100% sensitivity and specificity at both 6 and 20 hours. The mCIM test had a sensitivity of 90.81% at 6 hours, increasing to 94.89% at 20 hours, with specificities of 72.72% and 86.36%. The combination disc test had a sensitivity of 98.57% for KPC(A), 100% for OXA-48(D) and NDM+OXA-48 (B+D), 50% for OXA-23+OXA-51 (D) and 0% for NDM+KPC (B+A) isolates. The rapid test demonstrated 100% sensitivity. CONCLUSIONS: The rapid test's high sensitivity, simplicity, and full agreement with PCR results suggest its suitability for routine laboratory use. The combination disk test also offers a reliable alternative for detecting carbapenemase production, particularly when considering local resistance patterns.