Systematic comparison of four methods for the detection of carbapenemase-producing Enterobacterales (CPE) directly from blood cultures

Maria Meier, Axel Hamprecht
Journal of Clinical Microbiology 2019 August 14
Early identification of infections caused by carbapenemase-producing Enterobacterales (CPE) can help to optimize patient treatment and improve outcome. In this study, protocols for rapid detection of carbapenemase production directly from positive blood cultures were developed applying a concentration and hemolysis step before a test for carbapenemase production was performed. Four different methods (three modified colorimetric assays [β-Carba, bcCarba NP and NeoRapid Carb] and a variation of the CIM test [bcCIM]) were assessed on blood cultures spiked with 185 different molecularly characterized Enterobacterales isolates. The challenge collection included 81 carbapenemase-negative isolates and 104 CPE (OXA-48 [n=25], NDM [n=20], KPC [n=18], VIM [n=25], GIM [n=5], OXA-48-Iike [n=9], OXA-48-like + NDM [n=2]). The sensitivity/specificity was 99.0%/95.1% for bcCarba NP, 99.0%/91.4% for NeoRapid Carb, 100%/95.1% for β-Carba and 100%/100% for bcCIM. Weakly hydrolyzing carbapenemases (e.g. OXA-48-like) were also well detected by the assays. The time-to-result was 20-45 min for β-Carba, 2-3 h for bcCarba NP 2.5-2h for NeoRapid Carb and 18-24 h for bcCIM. In conclusion, all assays demonstrated a good detection of CPE. The protocols can be easily implemented in any clinical microbiology laboratory and could help to early optimize therapy in bloodstream infections by CPE.


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