Enhanced detection of carbapenemase-producing Enterobacteriaceae by an optimized phenol red assay

Screening for the detection of carbapenemase-producing bacteria still encounters issues related to workflow, limit of detection, or qualitative interpretation. We developed a spectrophotometry-based version of the Carba NP phenol red assay (Nordmann et al., 2012) in a microtiter plate format, compatible with low bacterial cell counts. We were able to detect highly active carbapenemases such as KPC and IMP in 30min. A wider range of carbapenemases including OXA-48 were detected using higher inocula, still being competitive compared with currently available phenol red assays. Validation experiments of our test with a panel of 81 Enterobacteriaceae showed good performance with 93% of sensitivity and 92% of specificity. The compatibility of our routine-friendly protocol with automation offers great perspectives for high throughput screening in outbreak situations and/or in big laboratories. [Display omitted] •Spectrophotometry-based phenol red assay for carbapenemase detection•The test can be performed with low amount of bacteria.•The performance is comparable to that of currently used commercial tests.•The assay is cost-efficient, routine-friendly and compatible with automation.