Systematic Comparison of Four Methods for Detection of Carbapenemase-Producing Enterobacterales Directly from Blood Cultures

Abstract

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.

Blood-Modified Carbapenem Inactivation Method: a Phenotypic Method for Detecting Carbapenemase-Producing Enterobacteriaceae Directly from Positive Blood Culture Broths

“…Second, we only assessed this method using a single blood culture system at one center. Again, this appears to be a limitation of previous studies (17,18). Finally, an 18 to 24 h of incubation step is required to evaluate meropenem zone sizes.…”

“…Notwithstanding the favorable performance of the Blood-mCIM, our study has limitations. First, only contrived blood culture broths were assessed, although this appears to be a limitation of most studies assessing the performance of phenotypic methods for detecting carbapenemase activity directly from positive blood culture broths (17,18). Second, we only assessed this method using a single blood culture system at one center.…”

“…Several phenotypic methods for the detection of carbapenemase-producing isolates directly from positive blood culture broths have been reported. These include modifications of the Carba NP, ␤-CARBA, CIM, and NeoRapid CARB tests (17,18). The reported diagnostic sensitivity of these assays varied between 97.9 and 100%, and the diagnostic specificity between 91.4 and 100%.…”

A Four-Hour Carbapenem Inactivation Method (CIMB.S) Using Bacillus stearothermophilus as Indicator Strain

“…A rapid carbapenem inactivation method (rCIM) was recently developed that could detect CPE within 3 h, but it required automated turbidity measurements, which may be a restriction for some clinical laboratories (21). Some researchers have attempted shorter incubation periods of the disk on the indicator strain (8 h), aiming to reduce incubation time of mCIM, but it is still time-consuming (22).…”

“…The major limitation of this study is that the tested carbapenemresistant Gram-negative bacteria only possessed several prevalent carbapenemases, in particular lacking the genotype like OXA-48, which is necessary to further study. In addition, we did not examine clinical samples of blood and urine, but these samples could be applicable because a carbapenem hydrolysis test for these sample types has been developed (22). Evaluation of the CIM B.S assay to detect clinical samples is worthy of further study.…”