Performance of the BD Phoenix CPO detect assay for the detection and classification of OXA-48 producing-Escherichia colithat do not coproduce ESBL/pAmpC

Reliable detection of OXA-48-like enzymes in routine antimicrobial susceptibility testing is difficult, especially if the isolate does not coproduce other beta-lactamases. The BD Phoenix™ Emerge panel includes the CPO Detect Test (CPO-T), which allows simultaneous antimicrobial susceptibility testing and carbapenemase detection and characterization. We evaluated the accuracy of detection and classification of carbapenemases determined by CPO-T against a characterized set of OXA-48-producingEscherichia coliisolates that do not co-produce ESBL/pAmpC, and BD PhoenixTMfor rapid antimicrobial susceptibility testing. A total of 51E. coliisolates were included All the isolates were sequenced using Illumina and analyzed using Resfinder and CARD for resistance determinants, MLSTfinder for typing and Clermont Phylotyper for phylotypes. CPO-T was performed within the BD Phoenix™ NMIC-502 panel. Disk diffusion, with readings at 4, 6, 8 and 24 hours, was performed as reference method (RDD). The CPO-T detected carbapenemase activity in 100% of the isolates within 7 hours of incubation and 42 (82.4%) isolates were correctly assigned to the class D Ambler. For all isolates and antibiotics, BD Phoenix™ provided definitive susceptibility results in less than 8 hours in 64.6% of cases compared to 58.2% with RDD. Overall categorical agreement was 90.7% and 5.9% very major, 6.2% major and 3.2% minor errors were observed.Our results demonstrate that CPO-T is a reliable tool for the detection of OXA-48 inE.coliisolates that do not co-produce ESBL/pAmpCwithout the need for additional testing, and that BD Phoenix™ provides rapid results for the antibiotics most commonly used in empirical treatment.