Detection of carbapenemase activity in Enterobacteriaceae using LC-MS/MS in comparison with the neo-rapid CARB kit using direct visual assessment and colorimetry

Abstract

It has been described that the sensitivity of the Carba NP test may be low in the case of OXA-48-like carbapenamases and mass spectrometry based methods as well as a colorimetry based method have been described as alternatives. We evaluated 84 Enterobacteriaceae isolates including 31 OXA-48-like producing isolates and 13 isolates that produced either an imipenemase (IMP; n=8), New Delhi metallo-β-lactamase (NDM; n=3), or Klebsiella pneumoniae carbapenemase (KPC; n=2), as well as 40 carbapenemase negative Enterobacteriaceae isolates. We used the Neo-Rapid CARB kit, assessing the results with the unaided eye and compared it with a colorimetric approach. Furthermore, we incubated the isolates in growth media with meropenem and measured the remaining meropenem after one and 2h of incubation, respectively, using liquid chromatography tandem mass spectrometry (LC-MS/MS). Whilst all carbapenemase producing isolates with the exception of the OXA-244 producer tested positive for both the Neo-rapid CARB test using the unaided eye or colorimetry, and the 13 isolates producing either IMP, NDM or KPC hydrolysed the meropenem in the media almost completely after 2h of incubation, the 31 OXA-48-like producing isolates exhibited very variable hydrolytic activity when incubated in growth media with meropenem. In our study, the Neo-Rapid CARB test yielded a sensitivity of 98% for both the traditional and the colorimetric approach with a specificity of 95% and 100% respectively. Our results indicate that the Neo-Rapid CARB test may have use for the detection of OXA-48 type carbapenemases and that it may be particularly important to ensure bacterial lysis for the detection of these weaker hydrolysers.

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

“…The specificity of the NeoRapid CARB was slightly lower than for the other tests. However, other studies show similar results on isolates grown on solid medium, with sensitivity and specificity values ranging from 89% to 100% and 70% to 100%, respectively (11, 13, 14).…”

Diagnostic Accuracy of Carba NP test for Rapid Detection of Carbapenemase-Producing Enterobacteriaceae: Systematic Review and Meta-Analysis

“…Although molecular methods are considered the gold standard for CRE detection, they less commonly used because of their high cost and the need for special laboratory facilities [34][35][36] , therefore, many phenotypic methods which are fast, accurate, and cheap have been suggested, the most common one is Carba NP test 7,[37][38][39] .…”

“…On the other hand, the difference in the geographic and genetic distribution of carbapenemases might be another factor explains the heterogeneity in this study. The presence of OXA-48-like carbapenemases remarkably reduce the sensitivity of Carba NP test, because of its low hydrolysis activity 12,39 . This class of carbapenemase is rare in the USA.…”

One System for All: Is Mass Spectrometry a Future Alternative for Conventional Antibiotic Susceptibility Testing?

“…The fully quantitative technique allows the detection of minor changes in antibiotic concentration (Peaper et al, 2013), in particular when internal standards are used (Wang et al, 2013b). As substrate antibiotics, meropenem (Foschi et al, 2015), ertapenem (Peaper et al, 2013), and imipenem (Kulkarni et al, 2014) have been deployed to detect carbapenemase (OXA-48, IMP, NDM, and KPC) activity in Enterobacteriaceae (Huber et al, 2016; Tadros et al, 2018), Acinetobacter baumannii (Lin et al, 2016), and other taxa. The technique can potentially be applied equally widely as the MALDI antibiotic degradation assay, except for the same limitations discussed above.…”