Phenotypic detection and differentiation of carbapenemase classes including OXA-48-like enzymes in Enterobacterales and Pseudomonas aeruginosa by a highly specialized MICRONAUT-S microdilution assay.

Objectives: The objective of this study was to evaluate the MICRONAUT-S Carbapenemases Detection microtiter plate assay for detection of carbapenemases and Ambler class determination. Methods: The MICRONAUT-S Carbapenemases Detection microtiter plate was tested using a challenging collection of 154 carbapenemase-producing and 150 carbapenemase-negative clinical strains of Enterobacterales and Pseudomonas aeruginosa. Results: The MICRONAUT-S Carbapenemases Detection assay was able to detect 148/154 carbapenemase producers correctly, while 5/150 non-carbapenemase producing isolates were tested false-positive. This resulted in an overall sensitivity of 96 % and a specificity of 97 %. Regarding detection of the class of carbapenemase, sensitivities and specificities were 93 %/100 %, 96 %/100 and 97 %/99 % for class A (n = 27), class B (n = 54) and class D (n = 73) carbapenemases, respectively. Conclusions: The MICRONAUT-S Carbapenemases Detection microtiter plate represents an easy-to-use and valuable tool for accurate and reliable detection of carbapenemases. In addition, it provides identification of the class of carbapenemase in most cases which can provide significant therapy guidance.