Performance Evaluation of Diagnostic Assays for Detection and Classification of Carbapenemase-Producing Organisms

Rapid and accurate detection can help optimize patient treatment and improve infection control against nosocomial carbapenemase-producing organisms (CPO). In this study, a total of 217 routine clinical isolates (Enterobacterales and A. baumannii), including 178 CPOs and 39 non-CPOs, were tested to evaluate the performance of six phenotypic carbapenemase detection and classification assays, i.e., BD Phoenix CPO detect panel, Rapidec Carba-NP, O.K.N detection kit, and three carbapenem inactivation methods (CIMs; mCIM, eCIM, sCIM). The overall detection sensitivity and specificity were 98.78% (95.21-99.79%) and 79.49% (63.06-90.13%), respectively, for the BD phoenix CPO P/N test; 91.93% (86.30-95.45%) and 100% (88.83-100%), respectively, for the Rapidec Carba-NP; 98.06% (94.00-99.50%) and 97.44% (84.92-99.87%), respectively, for mCIM; and 96.89% (92.52-98.85%) and 94.87% (81.37-99.11%), respectively, for sCIM. The classification sensitivity and specificity for the BD phoenix CPO Ambler test, the O.K.N detection kit, and the mCIM and eCIM were 56.71% (48.75-64.34%) and 94.87% (81.37-99.11%), 99.28% (95.43-99.96%) and 100% (88.83-100%), and 92.90% (87.35-96.23%) and 97.44% (84.92-99.87%), respectively. All detection assays were reliable in detecting carbapenemase. However, the Rapidec Carba-NP and mCIM were insufficient in detecting OXA-48-like enzymes. The BD phoenix CPO detect panel had a strong ability to detect carbapenemase but failed to classify 48/59 (81.36%) KPC, 8/52 (15.38%) NDM, 8/22 (36.36%) OXA-23-like, and 6/11 (54.55%) dual enzymes. The O.K.N detection kit accurately detected and differentiated KPC, NDM, and OXA-48-like enzymes existing alone or in combination. The results of this study will support reliable laboratory work tools and promote therapeutic and infection control decisions.