Evaluation of the BD MAX Check-Points CPO Assay for the Detection of Carbapenemase Producers Directly from Rectal Swabs

A novel real-time multiplex PCR assay, BD MAX Check-Points CPO, was evaluated to detect carbapenemase-producing organisms in clinical settings on the BD MAX system. A total of 175 well-characterized isolates (including 123 carbapenemase producers) and 128 rectal swab specimens (including 83 positives) of patients considered at high risk for carriage of carbapenemase producers were included. Bacterial suspensions were used to spike true-negative rectal swabs to mimic a clinical sample. Sample (50 μL), containing either the spiked or the patient's sample, was processed. The BD MAX Check-Points CPO assay detected carbapenemases KPC, VIM/IMP, NDM, and OXA-48-like producers with a high sensitivity and specificity of 97.1% and 98.8%, respectively. Rare variants of the IMP type (IMP-11, IMP-13, and IMP-14) and one rare and distantly related OXA-48 variant (OXA-535) remained undetected. With patients' rectal swabs, sensitivity and specificity were 92.8% and 97.8%, respectively. Failure of detection was due to weak inoculum. The time to result was short: approximately. 2.5 hours for 12 samples (including extraction and PCR). The automated sample-in results-out platform is an efficient, quick, and easy-to-use tool for the detection of the main five carbapenemases. The lack of distinction between producers of VIM and IMP may be limiting in countries where these enzymes are widespread, as in Asia, but not in France, where IMP producers are extremely rare.