Background: Rapid and accurate methods for detecting carbapenemase-producing Enterobacterales (CPE) are essential for improving patient prognosis and preventing the spread of these microbes. In this study, 103 carbapenem-resistant Enterobacterales (CRE) isolates were collected from clinical specimens; of these, 55 CRE isolates were included in the retrospective analysis, and 48 CRE isolates were included in the prospective evaluation. Using sequencing results as the gold standard, we evaluated the performance of the rapid carbapenem inactivation method (rCIM) for detecting carbapenemases in comparison with the modified carbapenem inactivation method (mCIM) and CNPt-Direct test. In rCIM, the test isolate was incubated with meropenem (MEM) disks, and the supernatant obtained via centrifugation was incubated with the indicator strain Escherichia coli ATCC 25922. Growth of the indicator strain was monitored using a nephelometer.
Results: The cut-off value of rCIM was 0.50 McFarland units. In retrospective analysis, the percent positive agreement and percent negative agreement of rCIM for detecting carbapenemase were 97.1% and 100%, respectively, and these values were higher than those for mCIM and the CNPt-Direct test. In the prospective evaluation, rCIM was linked to a sensitivity and specificity of 96.4% and 95%, respectively.
Conclusion: rCIM may be a rapid (<3 h), economical, simple, and reliable method for screening CPE isolates, and it is expected to be routinely implemented in clinical microbiology laboratories.